HYDRAULIC PARAMETERS DETERMINATION IN MINE WATER OF THE ABANDONED EDENDALE LEAD MINE USING TRACER TESTS

DETERMINATION OF HYDRAULIC PARAMETERS IN MINE WATER
OF THE ABANDONED EDENDALE LEAD MINE USING TRACER TESTS
by
Mpho Penelope Mokone
Submitted in partial fulfilment of the requirements for the degree
MAGISTER TECHNOLOGIAE: ENVIRONMENTAL MANAGEMENT
Department of Environmental, Water and Earth Sciences
FACULTY OF SCIENCE
TSHWANE UNIVERSITY OF TECHNOLOGY
SARChl Chair for Mine Water Management
Supervisor: Prof. Dr habil. Ch. Wolkersdorfer
May 2017

DECLARATION
I hereby declare that this dissertation submitted for the degree M Tech:
Environmental Management at the Tshwane University of Technology is my
original work and has not previously been submitted to any other institution of
higher education. I further declare that all sources cited or quoted are indicated
and acknowledged by means of a comprehensive list of references.
Mokone Mpho Penelope
208003879
i

Copyright © Tshwane University of Technology 2017
ii

ACKNOWLEDGMENTS
I would like to express my gratitude to my supervisor Professor Christian
Wolkersdorfer, for granting me the opportunity to study my MTech degree under
his supervision and guidance. I would like to thank him for his endless
encouragement and assistance in the field, for his valuable time that he gave for
all our discussions and all the lessons he gave for presentations and tips and
tricks of writing. I am thankful for his patience and for believing in me. It was
indeed a great privilege to work with him and I am thankful for all the time he spent
with me through to the completion of this dissertation. It would certainly be an
honour to work with him in the future.
Special thanks to Mr Thando Majodina, Geology Lecturer at the Tshwane
University of Technology for his assistance and time. To my fellow M-tech mates
who have become my second family, Lwazi, Busisiwe, and Kagiso; I appreciate
their assistance in the field and encouragement in the office all their support.
iii

PRESENTATIONS AND PUBLICATIONS
The work contained in this thesis has previously been presented at conferences as
indicated below.
Conference Presentations
Mokone, M. P. & Wolkersdorfer, C. The Determination of Hydrodynamic
Processes and Mine Water Quality at the Abandoned Edendale Lead Mine By
Stratification. Poster presentation. Tshwane University of Technology, Faculty
Research Day. 9 September 2016, Pretoria, South Africa.
Mokone, M. P. & Wolkersdorfer, C. Tracer Test in Mine Water of the Abandoned
Edendale Lead Mine, South Africa. Oral presentation. 13th International Mine
Water Association Congress. 25 – 30 June 2017, Rauha, Lappeenranta, Finland.
Publications
Mokone, M. P. & Wolkersdorfer, C. Tracer Test in Mine Water of the Abandoned
Edendale Lead Mine, South Africa. IMWA 2017 – Mine Water & Circular Economy
(Vol I), proceedings: 342-350.
iv

ACKNOWLEDGEMENT
Most of all to my parents I am grateful for them being supportive and encouraging
me to further my studies and the faith they have in me.
Mrs Zicki Jourbert, in the Department of Environmental, Water and Earth Science,
I would like to thank her for ensuring that all things ran smoothly throughout the
dissertation, from registration, field transportation including reagents needed for
both the laboratory and field all the equipment and software which were required
during the study. She has been a blessing.
I would like to acknowledge the Water Lab for the laboratory results of the water
quality analyses which they always sent on time in an orderly manner.
Great thanks to the Tshwane University of Technology, the Department of
Environmental, Water and Earth Sciences for allowing me to carry out this study.
v

ABSTRACT
The purpose of this study is to determine hydraulic connectivity by conducting a
tracer test and to establish an understanding of the hydrodynamic processes
through stratification in the mine water of the abandoned Edendale Lead Mine with
the aim of identifying potential mine water pollution and classifying the mine water
quality. This study was conducted at the abandoned Edendale Lead Mine which is
located on the farm Nooitgedagt 333JR in Silverton, Pretoria east one of the
earliest mines in the Transvaal region and operated from 1890 to 1974. Water
samples were collected at the shafts, discharge point and Edendalespruit up and
downstream and analysed for main ions and trace elements using ion
chromatography and ICP-MS or ICP-OES. In addition, on-site parameters were
measured with Hach instruments. A dipper was used for stratification
measurements in the three shafts of Edendale Lead Mine and 21 kg of food quality
NaCl were dissolved in 75 L of tap water the solute was then used as a tracer and
injected into one shaft. The mine water discharging from the mine and also in the
mine shafts when measuring on-site parameters indicated that the pH 6-8,
circumneutral pH, with a oxidation-reduction potential electrode between 90 and
500 mV this influences ion exchange in mine water, dissolved oxygen percentage
below 90% and dissolved oxygen concentration lower than 20 mg/L this could be
because of bacteria which use up the oxygen or the biological oxygen demand by
plants in the Edendalespruit stream water and also because of the water warmth.
Pb, Ag and Sb were below detection limit, high silicon concentration was detected
vi

at all sites but higher at the downstream. Ca and K elevated at the discharge point
and Mg and Na found high downstream. SO42- high as 102 mg/L downstream and
55 mg/L upstream. Stratification in the three shafts was not stable, high EC was
observed at great deeper water level and at lower temperatures and lower EC
waters above at substantially high temperatures. During the tracer test, the
electrical conductivity increased in the wet months. Only 17.1% of the injected
tracer was recovered. The fact that the mine water is stratified demonstrates that
chemical and hydrodynamic processes seem to favour a mine water stratification.
Based on the results, it can be concluded that there is mineralisation and possible
contamination. However, it can be concluded from the tracer test that the flow is
adjective. Yet, the results obtained so far show that there will be not deteriorating
contamination of the receiving watercourses.
vii

TABLE OF CONTENTS
PAGE
DECLARATION.....................................................................................................................................i
ACKNOWLEDGMENTS.......................................................................................................................ii
PRESENTATIONS AND PUBLICATIONS...............................................................................................iii
Conference Presentations........................................................................................................iii
Publications..............................................................................................................................iii
ACKNOWLEDGEMENT......................................................................................................................iv
ABSTRACT..........................................................................................................................................v
LIST OF FIGURES...............................................................................................................................xi
LIST OF TABLES.................................................................................................................................xv
LIST OF ABBREVIATIONS.................................................................................................................xvi
1 INTRODUCTION.........................................................................................................................1
1.1 Background And Justification............................................................................................1
1.2 Research Problem..............................................................................................................5
viii

1.3 General Aims and Objectives.............................................................................................6
2 LITERATURE REVIEW.................................................................................................................8
2.1 CHEMISTRY OF MINE WATER............................................................................................8
2.1.1 Mineral dissolution as a source of contamination.....................................................8
2.1.2 Mobility of contaminants - effects of pH.................................................................14
2.1.3 Pyrite and sulphide mineral weathering..................................................................20
2.2 STRATIFICATION..............................................................................................................29
2.2.1 Stratification of lakes...............................................................................................29
2.2.2 Stratification of underground mines........................................................................32
2.3 MINE WATER AND GROUNDWATER AQUIFER.................................................................36
2.3.1 Characteristics of mine water aquifers and mine pools...........................................36
2.3.2 Aquifer parameters..................................................................................................39
2.3.3 Interaction of mine water and groundwater...........................................................42
2.4 TRACERS AND TRACER TESTS IN UNDERGROUND MINES................................................44
2.4.1 Types of tracers.......................................................................................................44
2.4.2 Applications of tracing tests....................................................................................46
ix

2.4.3 Assessment and simplification of tracer tests..........................................................49
2.5 ENVIRONMENTAL EFFECTS OF MINE WATER DISCHARGE...............................................51
2.5.1 Impacts on human health and aquatic life...............................................................51
2.5.2 Impacts on water resources....................................................................................54
3 METHODOLOGY......................................................................................................................55
3.1 DESCRIPTION OF STUDY AREA.........................................................................................55
3.1.1 Geological setting and study area............................................................................56
3.1.2 Climate and hydrology.............................................................................................59
3.1.3 Mining history..........................................................................................................60
3.2 DATA COLLECTION...........................................................................................................65
3.2.1 Mine water chemistry..............................................................................................65
3.2.2 Sample collection procedures..................................................................................66
3.2.3 Stratification............................................................................................................68
3.2.4 Mine water tracing..................................................................................................69
3.2.5 Analytical methodology...........................................................................................69
4 RESULTS AND DISCUSSION......................................................................................................71
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4.1 Introduction.....................................................................................................................71
4.2 On-site parameters..........................................................................................................71
4.3 Water Chemistry.............................................................................................................79
4.4 Statistical Analysis...........................................................................................................83
4.5 Stratification....................................................................................................................84
4.6 Tracer test.......................................................................................................................92
5 CONCLUSION AND RECOMMENDATIONS................................................................................95
6 REFERENCES............................................................................................................................96
APPENDIX I....................................................................................................................................117
Water Samples co-ordinates.........................................................................................................118
xi

LIST OF FIGURES
PAGE
Figure 2.1: Solubility of metals as a function of p H (from Cravotta, 2008)............14
Figure 2.2: Stability diagram for Sb-species in the Sb – S – H2O system (from
Filella et al., 2002)...................................................................................................15
Figure 2.3: Eh – pH diagram for zinc ( from Nuttall et al., 2000)............................17
Figure 2.4: Pyrite oxidation simplified diagram showing reaction pathway (from
Banks et al., 1997)..................................................................................................21
Figure 2.5: Stratification of lakes (from UFI, 1994).................................................27
Figure 2.6: Temperature and specific conductivity profile of Cueva de la Mora Pit
Lake (from España et al., 2009).............................................................................29
Figure 2.7: Development of stratification in mine water in a shaft and how it is lost
(from Nuttall et al., 2004)........................................................................................30
Figure 2.8: Conductivity and temperature log of No. 2 Shaft at Frazer's Grove Mine
(from Johnson et al., 2002).....................................................................................32
xii

Figure 2.9: Schematic depiction of the vertical zonation of the dolomite in the FWR
based on the degree of karstification/ fracturing and storativity (according to Winde
et al. (2006).............................................................................................................37
Figure 2.10: Bimodal breakthrough curve for the January 2001 tracer experiment,
represented as tracer flux. The curve is decomposed in 2 signals, each
corresponding to one impulse injection of tracer (0.5 and 1 kg respectively),
showing a linear behaviour of the system with respect to mass transport. (Massei
et al 2006)...............................................................................................................46
Figure 2.11: Residence time distribution for each tracer test (peak areas = 1).
Residence time distributions ordinates are H(t)=tracer flux/recovered mass.
Massei et al 2006....................................................................................................47
Figure 3.1: Overview of three shafts of the abandoned Edendale Lead Mine
(Google Earth, 2004 http://earth.google.com; Datum WGS84, geographical
coordinates, without scale).....................................................................................52
Figure 3.2: The three main outcrops of Kaapvaal craton, Kanye basin in Botswana,
Griqualand West basin and the Transvaal basin (from Eriksson et al., 2012).......55
Figure 3.3: Cross section of the Edendale No 1 Mine 1903 – 1909 (From Reeks,
2012).......................................................................................................................59
xiii

Figure 3.4 Cross section of the Edendale (Union Silver and Lead Ltd) No 2 Mine
1937 (from Reeks, 2012)........................................................................................60
Figure 4.1: pH from the abandoned Edendale Lead Mine.....................................70
Figure 4.2: Redox (mV) from the abandoned Edendale Lead Mine.......................71
Figure 4.3: Electrical Conductivity (μS/cm) from the abandoned Edendale Lead
Mine.........................................................................................................................73
Figure 4.4: Temperature (°C) from the abandoned Edendale Lead Mine..............74
Figure 4.5: Dissolved Oxygen (mg/L) from the abandoned Edendale Lead Mine. 75
Figure 4.6: Dissolved Oxygen (%) from the abandoned Edendale Lead Mine......75
Figure 4.7 Element concentration...........................................................................79
Figure 4.8: Piper diagram for samples collected at the abandoned Edendale Lead
Mine; n = 15, averages of three sampling campaigns............................................79
Figure 4.9: Stratification on shaft E01, E12 and E13 in the abandoned Edendale
Lead Mine January 2016........................................................................................83
xiv

Figure 4.10: Stratification on shaft E01, E12 and E13 in the abandoned Edendale
Lead Mine in March 2016.......................................................................................84
Figure 4.11: Stratification on shaft E01, E12 and E13 in the abandoned Edendale
Lead Mine in April 2016..........................................................................................85
Figure 4.12: Stratification on shaft E01, E12 and E13 in the abandoned Edendale
Lead Mine in June 2016..........................................................................................86
Figure 4.13: Stratification on shaft E01, E12 and E13 in the abandoned Edendale
Lead Mine in July 2016...........................................................................................87
Figure 4.14 Stratification on shaft E12 and E13 in the abandoned Edendale Lead
Mine in August 2016...............................................................................................88
Figure 4.15: Stratification on shaft E12 and E13 in the abandoned Edendale Lead
Mine September 2016.............................................................................................88
Figure 4.16: EC measurement in shaft E13 and discharge point of the abandoned
Edendale Lead Mine during tracer test...................................................................90
Figure 4.17: Recovery rate of the Edendale tracer test..........................................91
xv

LIST OF TABLES
PAGE
Table 3.1: Coordinates for each of the sample sites..............................................53
Table 3.2: Names used at the Edendale mine during operation (modified from
Reeks, 2012)...........................................................................................................58
Table 3.3: Instruments used to measure on-site parameters in the field...............63
Table 4.1: On-site parameters from the abandoned Edendale Lead Mine. n: on-
site parameter; ± is standard deviation of sample population. Average of the pH
calculated using the [H+].........................................................................................68
xvi

LIST OF ABBREVIATIONS
AMD: Acid Mine Drainage
DO: Dissolved Oxygen
DWAF: Department of Water Affairs
EIA: Environmental Impact Assessment
ELM: Edendale Lead Mine
EPA: Environmental Protection Agency
EU: European Union
GDP: Gross Domestic Product
GPS: Global Positioning System
IC: Ion Chromatography
ICP-MS: Inductively Coupled Plasma– Mass Spectrometry
ICP-OES: Inductively Coupled Plasma– Optical Emission Spectrometry
NEMA: National Environmental Management Act 107 of 1998
NWA: National Water Act 36 of 1998
xvii

ORP: Oxidation Reduction Potential
SAC: South African Constitution 108 of 1996
SANS: South African National Standards
TDS: Total Dissolved Solids
TWQR: Target Water Quality Range
WHO: World Health Organisation
xviii

1 INTRODUCTION
1.1 BACKGROUND AND JUSTIFICATION
In many parts of the world, mining is known as one of the major economic
contributors as it provides resources used in modern industrial society in both
developing and developed countries. In South Africa mining play an important part
in the economy contributing 30% to the country’s gross domestic product (GDP)
employing millions of people and paying R10.5 billion to tax (Chimhanda, 2010;
Van Der Schyff, 2012). However, globally mining is known as one of the main
cause of environmental concerns.
The quality and quantity of water resources and their surrounding environment are
substantially influenced by mining activities. The case in Randfontein,
Johannesburg ## (Cidu et al., 2008; Wolkersdorfer, 2008). Moreover, mining can
lead to the pollution of soil and water, topographical changes, degraded land and
reduced ecological footprint (Yenilmez et al., 2011). Worldwide changes in the
mining sector have led to the closure of many long-established deep mines
because of economic and environmental reasons (Adams et al., 2001).
In South Africa, legislation and guidelines have been adopted to address mine
closure and post-mining water management even so abandoned mines remain a
liability (Kgari et al., 2016). The South African Constitution (108 of 1996) is aimed
at reducing environmental impacts associated with mining activities providing
1

sustainable development it states the priority of environmental protection for
present and future generation beneficiaries giving everyone a right to a clean and
healthy environment. Water resources near mines are preserved by the National
Water Act (36 of 1998) that strive for ecosystem sustainability and commands
water users to prevent or minimize contamination of water resources and
authorizes water uses promoting the reduced water uses and pollution of
resources. Furthermore, the Best Practice Guidelines for Water Resource
Protection is aimed to apply cleaner production techniques to protect water
resources and prevent pollution at source. In 2002 the Minerals and Petroleum
Resources Development Act No. 28 (MPRDA) was adopted and is used as a
policy to govern the exploration of minerals in South Africa pre/post-mining life
cycle. It necessitates the procedures of Environmental Impact Assessment (EIA)
along with the National Environmental Management Act (No. 107 of 1998) that
legislates polluters to take responsibility to minimize and mitigate pollution.
Silver mining in South Africa started around 1880 when the “Pretoria Silver Belt”
prospected in Pretoria, Gauteng Province. Consequently, the development of
mineral mining grew countrywide and as a result, many of the smaller mines were
abandoned (Kgari et al., 2016; Reeks, 2012).
When mines are abandoned, the rebound of the water table can lead to
contaminated groundwater to flow into underlying aquifers causing degradation to
the quality of receiving surface water and groundwater, eventually making it
unsuitable for further use (Cidu et al., 2007; Wolkersdorfer, 2005; Younger et al.,
2005). Environmental problems associated with abandoned mines are controlled
2

by the type of mining employed (underground or surface mining). Approximation of
mine water quality draining from surface mines is well developed but such is more
or less absent in abandoned flooded underground mines.
The flooding of underground mines might cause the supporting structures to
collapse and subside causing inaccessibility to the shafts or adits of the mine. This
further increases the permeability and porosity and alters the groundwater flow as
the underlying aquifer becomes fractured (Booth et al., 1998; Mhlongo et al., 2016;
Younger, 2000b). Hydrodynamics governing the movement and transport of mine
water in flooded underground mines is not commonly acknowledged in South
Africa. The general focus of most investigations in South Africa has been on
contamination treatment and inhibition of water discharge (Kgari et al., 2016).
However, planning remediation strategies and the calculation of reactive transport
within the mine depend on the understanding of the volume of flooded mines and
hydraulic properties (Wolkersdorfer, 2005).
Tracer tests have been employed to trace the hydrodynamic conditions of flooded
underground mines and interconnections of groundwater flow. The publications of
tracer tests results in abandoned underground mines are not commonly known.
Therefore, there is less experience in mine water tracing. Tracers are used
depending on site conditions and aims (Wolkersdorfer et al., 2002). Although, in
the past, tracer techniques focused on groundwater flow in karstic aquifers, there
has been developed in previous decades for the use of tracers as a hydrologic
investigating tool. Tracers are inferred to as any constituent which by design is
introduced into the aquifer to determine flow paths, groundwater velocities, mass
3

flow and contamination transport (Divine et al., 2005). Understanding the hydraulic
connection between mine workings, surface and groundwater is needed for source
determination of water and pollutants at the discharge point as so to support
remediation measures (Kgari et al., 2016).
4

1.2 RESEARCH PROBLEM
The study was conducted to investigate the potential mine water and
environmental pollution at the abandoned Edendale Lead Mine which is adjacent
to Edendalespruit rivulet. The water quality results were compared with the
international and national standard used to evaluate contamination of water and
the toxicity thereof to the aquatic system and for human welfare.
Mine water often contains potentially toxic concentrations of metals such as Fe, Al,
Cr, Cd, Ni, Pb, Co, Zn and Cu. They are produced from coal or metal mining. Acid
mine waters can have a pH-of –3.5 to 5, also at pH 6 – 8 which is called
circumneutral. Mine waters can have elevated (semi-)metal concentrations (e.g.
As, Mo, U, Sb) and F. Mine water discharging into rivers, lakes, streams or oceans
might seriously degrade the water quality and cause damages to aquatic life. As
described above, the main acid-producing process is the exposure of pyrite to
oxygen from air in the presence of water, which causes bacterial catalysed
oxidative dissolution (Nordstrom, 2011b). When abandoned mines need to be
redeveloped, it is, therefore, necessary to know the hydraulic parameters
(transmissivity, hydraulic permeability, dispersivity, porosity, storativity and
transivimmitivity) which are needed for planning remediation strategies as they
dictate where the mine water flows to.
Metals and metalloids may contaminate surface waters as a result of wreathing of
waste rocks when it rains the intrusion of rain into these waste rocks results in
metal flowing from these sites into receiving waters and transported downstream
5

as dissolved minerals, this may have a substantial influence on the river.
Increasing movement and biological availability of minerals, thus impacting on the
natural balance. Sediments are basins for pollutants in the aquatic environment
there have been generally acknowledged and as an outcome, it leads to
undesirable influences to the benthic ecosystem (Beane et al., 2016). This study
was relevant because there is a primary and high school nearby and the mine is
located adjacent to the Edendalespruit, where numerous farms and some private
residential areas rely on borehole water that might be polluted by the mine (Glass,
2006).
1.3 GENERAL AIMS AND OBJECTIVES
The main objectives of the present study were to determine the hydraulic
parameters in mine water in the abandoned Edendale Lead Mine with the aim of
identifying potential mine water pollution sources using tracer tests. In order to
achieve the main objectives, the following activities were carried out
i. Characterize the mine water quality, in terms of chemical analysis using
ICP-OS and Ion chromatography and onsite parameters
ii. Understand the hydrological situation around Edendale Lead Mine,
determine the stratification in mine water of the abandoned Edendale Lead
Mine.
iii. Conduct tracer test, tracer solute injection into shafts of the Edendale Lead
Mine to determine hydraulic connectivity.
6

2 LITERATURE REVIEW
2.1 CHEMISTRY OF MINE WATER
2.1.1 Mineral dissolution as a source of contamination
Groundwater chemistry is influenced by rock and water interactions also the
dissolution of minerals (Kumar, 2014). Dissolution occurs when there is contact
between water and rock-forming minerals thus chemical weathering occurs
(Matthess, 1982). According to (Andrews et al., 2013) when water especially acidic
water and oxygen attacks minerals this is known as chemical weathering and
dissolution is a type of chemical weathering in which soluble minerals dissolve.
According to Alam et al. (2014) when dissolution occurs the by-products of these
minerals results in contamination of groundwater as the concentration of mineral
composed in an aquifer and/or exposed by human activities is increased.
Minerals are naturally occurring they are found underground and on the surface in
ores, rocks and natural mineral deposits furthermore, these minerals are maybe
under oxidizing or reducing state in which dissolution or hydrolysis can
occur(Schreiber et al., 2013).
Underground mines have audits and shafts through which mine water may be
discharged, these openings are mined and allow sudden water intrusion when
mining has ceased, however, the water flowing in this openings will interact with
mineral sulphide in little time discharging water with low metal concentration and if
7

water accumulates and discharges at a lower flow rate mine pools are formed and
mine water flows into nearby aquifers (Nordstrom et al., 2015).
The EPA under the Safe Drinking Water Act defines a contaminant as “any
radiological, chemical, physical or biological substances or material which dissolve
in water may”. (Fetter, 2000) states that there are different types of water
contaminants which may migrate from groundwater to surface water vice versa
reaching the aquatic environment or affecting the water used by humans for
domestic, agricultural and recreational uses. These contaminate according to
Fetter, 2005 may be organic or inorganic chemicals, pathogens, and
hydrocarbons. EPA has listed inorganic chemicals as follows, Sb, As, Cu, Cn, Fe,
Al, Mn, Zn, Pb and anions (SO4 2-, Cl-, F-, NO3-) and cations (Mg, Ca, Na, and K).
Inorganic chemicals may also be referred to as metal and metalloids contaminate.
Mines are known to discharge mine water with elevated concentrations of
inorganic contaminants. According to (Wolkersdorfer, 2008), mine water has high
levels of trace element metals (copper, zinc, lead iron, and metalloids (arsenic and
antimony) including anions and cations such as sulphides and carbonates.
However, many trace element metals and/or metalloids are evaluated by the redox
process as they become hydrolysed because they exist in more than one oxidation
state the commonly found in mine water are:- Se[Se(IV), Se(VI)], Mn [Mn(II),
Mn(IV)], Cr[Cr(III), Cr(VI)], Cu [Cu(I), Cu(II), Fe [Fe(II), Fe(III) and As[As(III),
As(V)], (Luoma et al., 2008).
The major process that influences hydrogeochemistry cycle of elements globally
whereby water is the transport of dissolved particles from land to sea (Stumm and
8

Morgan, 2012). When the dissolution of minerals occurs there is an alteration of
rocks into soluble materials and soils into residues and sedimentary rocks (Stumm
et al., 2012).
Minerals may be categorized into primary, secondary, tertiary and quaternary
minerals. Primary minerals are those which are originally occurring in ore such as
silicates, carbonates and sulphides, when these minerals are oxidized they form
secondary minerals which include sulphide minerals such as gypsum and other
iron hydroxides when samples are taken the measured minerals such as calcium
and magnesium are regarded as tertiary minerals including sulphates such as
covellite however when samples are dried and stored the resulting minerals are
regarded as quaternary and they may be hydrated iron sulphide such as siderotil
or rozenite (Nordstrom et al., 2015).
Antimony occurs in the environment resulting from mining activities consequently it
is a naturally occurring metal (Okkenhuang, 2011). The common antimony
minerals are stibnite, valentinite, senarmontite, and cervantite. Antimony occurs on
group 15 of the periodic table it has similar properties as arsenic, it is a metalloid
which is considered harmful to both aquatic environment, human beings and
animals as it is commonly found in soils of abandoned smelters or mines (Fu,
2010). Antimony world reserves are found in South Africa, Mexico, China and
Russia where lead, copper and silver ores are mined (Filala, 2002).
In natural environments antimony is found in four [Sb (0), (-III), (III) and (V)]
oxidation states however, the common oxidation states are Sb (V) and it has been
9

stated that in aerobic conditions the Sb (V) is dominated while Sb (III) is found in
watery surroundings furthermore the antimony found in watery environment is
toxic as compared to the aerobic antimony (Wang, 2011) and (Okkenhaug, 2011).
Zinc is an abundant element that is listed 23rd commonly found element within the
earth (Flourance, 2014). The presence of zinc in the environment is sourced from
mining activities and it is found in concentrations of 1 μg/L through the dissolution
of rocks in mining areas or abandoned mines (Borrok et al., 2008). Sphalerite is
the major component of zinc and it is found in pyrite deposits including copper and
galena (Chandra et al., 2009). However, unlike other metals zinc is not redox
active (Borrok et al., 2008). Zinc can be found as free zinc ion (Zn2+) or attached to
other compounds such as oxides under aerated conditions and under anoxic
conditions, it attaches to sulphide and carbonates (Hofmann et al., 2008).
The sphalerite breakdown it releases sulphide and zinc ions, the process is
reversible as no solid species has been formed in equation 1. (Wolkersdorfer,
2008). According to Chandra et al. (2009), pure sphalerite is mainly made up of
zinc it constitutes 67 wt% of zinc, however, when sphalerite occurs in nature it has
some impurities and iron in high concentrations the two types of sphalerite may be
classified as high or low iron content sphalerite respectively.
ZnS + 2O2 → Zn+ + SO42- (1)
The zinc ions released in equation 1. when hydrolysed they release protons which
lower the pH in the aquatic environment and forms hydroxides, as in reaction 2
(Hofmann et al., 2008).
10

Zn+ + H2O Zn(OH)⟶ + + H+ (2)
Furthermore, the dissolution of sphalerite may be caused my catalyst such as
Thiobacillus ferrooxidant at very low pH after hydrolysis a condition best suitable
for ferrous iron to be oxidised to ferric iron this dissolution leads to ferric iron being
released into the aquatic environment as in reaction 3 (Hofmann et al., 2008).
ZnS + 2Fe3+ Zn⟶ 2+ + S+2Fe2+ (3)
The reactions show that zinc and other elements are transported into the aquatic
environment through the dissolution of sphalerite. When the dissolution of ZnS
occurs the metal concentration may be elevated and when hydrolysis results from
dissolution the pH can be lowered. When zinc is in the aquatic environment at
concentrations above the essential it can be harmful to both plants and animals
making its way through the food chain to humans.
The 34th element in the earth’s crust is lead which is found in group 14 on the
periodic table it is commonly used for industrial processes (Snogaass, 1986).
Furthermore, the uses of lead include the making of electric cables, roofing, piping,
and batteries (Lurie, 1981). Galena is the important mineral in which 90 % of lead
in the world is found other lead sources that contribute a small percentage are
cerussite and anglesite they occur when galena is altered by sulphide or/and
carbonates (Snogaass, 1986).
In the presence of dissolved oxygen dissolution of galena occurs as seen in
equation 4.
11

PbS + 2O2 → Pb2+ + SO42- (4)
Galena and sphalerite always occur together, however; galena comprises of silver
and other elements such as arsenic, antimony and bismuth whereas sphalerite
comprises of iron (Snogaass, 1986). According to Jones et al. (2013) in lead
mines, the expected metals in water resources are lead, zinc, sulphide, iron, and
cadmium they are products of the dissolution of galena and sphalerite.
When the dissolution of carbonates and sulphide minerals occurs there will be
elevated concentrations of calcium and sulphide in the receiving water resources
(Lee et al., 2005). Opencast mines cause contamination when minerals become
soluble upon contacting mine water in this way contaminants are released into the
environment (Stefania, 2005). Consequently, in aquatic environment when galena,
antimony and sphalerite are in dissolution they release protons, sulphide, iron and
other metals, the mobile lead and zinc ions are transported into the nearby water
resources this poses a direct or indirect threat to the well-being of humans and the
health of the ecosystem (Zhang et al., 2011).
Dissolution of minerals described by Navarro, 2008, a case where a substantial
influence on metal concentration resulting from sphalerite which gave off zinc,
cadmium, arsenic from pyrite and lead and copper from galena in Cabezo Rajao
abandoned mine which discharged into surface water thus river downstream.
2.1.2 Mobility of contaminants - effects of pH
The mobility of metals and semi-metals in mine water is influenced by the
12

concentration of major and minor trace elements, the understanding of elevated
metal concentration present in mine water discharge is essential in the
determination of environmental effects which mining poses to the aquatic
environment, surface water and groundwater (Milu et al., 2002).
The arithmetic expression used to express the activity of protons in water is known
as p H it is logarithmically represented and it implies that one pH unit change
symbolises a tenfold change to the proton activity which is the hydrogen ion,
equation 5. (Kay, 2014).
pH = − log10 [H+] (5)
The lowest pH ever measured was by (Nordstrom et al., 2000) at California’s Iron
Mountain the p H was −3.6. According to Kay (2014), the hydrogen activity in
acidic water has high hydrogen ion activity above 10×10-7 while for alkaline water
the activity is less than 10×10-7, naturally pure water has the p Hof 7 at a
temperature of 25°C.
Reduction-Oxidation reactions are defined by electron activity and it is recorded in
volts or millivolts, it measures the probability of electrons to be given off to electron
acceptors in a system (Kay, 2014). The stability limit of minerals depends on pH
and redox reactions; pH is known as the master variable in geochemical reactions
(Stumm et al., 2012).
Kay (2014) states that Redox measurements can be recorded as either electron
activity (pe) or quoted volts (Eh), the two are not interchangeable it is necessary
13

for the Eh measurement to be properly recorded because it is used in the
conversion of Eh to pe. The reason for the conversion process is explained by
Wolkersdorfer (2008) he states that the international redox standard required the
standard H2 electrode which is not suitable for field use, by the conversion the
results are obtained according to the standard H2 electrode. The Eh is converted
to pe by the following equation (Kay, 2014).
pe= f
2.303 RT Eh (5)
Where 2.303 is the conversion from natural log to base 10 log
T is the temperature expressed in K ([K] = [°C] + 273.15)
R is the gas constant (8.3144622 J K-1 mol-1)
F is Faradays, constant (96,485.3365 J V-1 g-1 [sA mol-1])
Eh, and pH values are useful in the construction of pourbaix diagrams which
illustrate the relationship between different minerals and the conditions in which
they are exposed to.(the dissolved species as a function of pH and metal stability
at a certain Eh value) (Al-Hinai et al., 2014). These diagrams are useful in
determining the mobility of certain elements.
Some elements are insensitive to pH, they are mobile and soluble over a huge pH
range these are commonly found in circumneutral mine waters which contain
metals and semi-metals (Zn, Cd, Se, Pb and As) Figure 2.1.
14

Figure 2.1: Solubility of metals as a function of p H (from Cravotta, 2008)
The stability diagrams have been used to explain the mobility of metals in the
aqueous environment, such has been seen in the study of Vink (1996) on which
he showed the stability of antimony. The speciation of antimony is controlled by
stability diagrams in the environment because antimony exists in both oxic and
anoxic environments (Filella et al., 2002). When the conditions favour oxidizing Sb
is immobile as it forms solid oxide species (Sb2O4 and Sb2O5) which precipitate into
sediments Figure 2.2 (Vink, 1996).
Other solid species Sb(OH)3 are formed under reducing conditions over a variety
of pH values between (3 – 10) however, when pH is extended above 10 Sb(OH)3
may dissolve forming Sb(OH)4- Figure 2.2 that is highly soluble and mobile under
the same reducing conditions when the pH is lower than 3 a soluble species
Sb(OH)2+ is formed (Filella et al., 2002).
In the presence of sulphur Sb2S3 (s) is formed when the pH is low, however, it is
replaced by SbS2 species at high pH this activity occurs under reducing conditions
15

(Filella et al., 2002). The mobility of antimony species depends on the pH and
redox, the release of antimony species into the environment is driven by these two
factors because transportation into receiving water environment transpires when
species are dissolved (in ionic form).
Figure 2.2: Stability diagram for Sb-species in the Sb – S – H2O system (from Filella et
al., 2002).
Although oxidation of antimony can be both pentavalent and trivalent in the
environment the Sb species are available and mobile regardless of the state of
oxidation and the mobility is affected by sorption more than it is by precipitation.
According to (Wilson et al., 2010) when Sb(OH)6- species are dominated there is
an increase in mobility of Sb(V) in acidic environments furthermore, the
16

occurrence of Sb(III) relates to the high presence of Sb2O3 which is not pH
dependent and it is consistent with Sb(OH)3 in aqueous system.
The hydroxyl groups are known to dissociate at high pH and give off hydrogen ion
when pH is low at the surface this results in both negative and positive charge
being given off, showing elevated antimony concentrations at low pH and
antimony oxides may be formed at pH above 12 (Cravotta, 2008).Furthermore, the
negative charges (oxides) adsorbs cations such as Cu, Zn, Ni, Pb and Cd while
positively charged adsorbs oxyanions such as selenite, selenite, sulphate,
arsenate, barate and arsenite at low pH.
Nuttall et al. (2000) in their study to remove zinc in circumneutral mine water
showed that sphalerite is steady in a wide pH variety in reducing environments
Figure 2.3 however, under oxidizing conditions at a p H of 7.5 – 8 zinc forms
smithsonite which precipitates this process happens in a closed system where
mine water is exposed to limestone. The free zinc ions can be seen at very low
and neutral pH (0 – 7) when sphalerite is oxidized. According to Nuttall et al.
(2000) zinc is less mobile when it forms ZnCO3 this process increases pH of mine
water in this way zinc is completely removed or the concentration is lowered from
circumneutral mine water.
Zinc hydroxides occur at very high pH occurs at oxidizing phase. These
hydroxides may dissociate at the surface or protonate as stated previously in the
case of antimony. Contamination of water resources and soils by zinc mobility is
dependent on the pH of the water and the redox condition.
17

Mobilization of contamination depends on the environment whether oxidising
and/or reducing conditions (Arhin et al, 2015) Under oxidising conditions sulphide
minerals are unstable and as a result, they release elements Fe, Pb, Cu, Zn and
As on water surface. Although these elements are considered toxic by WHO, 2014
established that Cu, Fe and Zn are essential to human beings but only at a certain
dosage but Baron, Ca, F, selenium is toxic even at low concentrations
When the conditions are oxidizing dissolved minerals interacts with either the
secondary or primary minerals releasing protons which decreases pH and
increases metal concentration (Fe, Cu, Pb, Hg, Ni, Co and Cd) and metalloids (Sb,
As, Al, Si, B, Mn and Li). It has been reported that pH depends on the chemical
composition of host rock when secondary minerals are formed the present metals
become immobile (Atanacković et al., 2013; Younger et al., 2004).
Figure 2.3: Eh-pH diagram for zinc ( from Nuttall et al., 2000)
18

2.1.3 Pyrite and sulphide mineral weathering
The weathering of pyrite and sulphide minerals occurs when mining activities
exposes these minerals to oxygen, water and/or microorganisms, this has caused
environmental problems because weathering results in metals being released or
transported into the receiving environment, aquatic or water resources for instant
pyrite releases iron while sphalerite releases zinc (Johnson et al., 2005).
The most abundant sulphide mineral on the crust of the earth is pyrite and it is
commonly associated with metals released from sulphide ores (Johnson et al.,
2005). Waste rocks, stockpiles or mine working comprises of pyrite and sulphide
minerals these minerals are prone to weathering and they release Zn, Hg Cd. Cu,
Cd, Ni, and Al in groundwater and flooded mine workings or water flowing from
these sites (Blowes et al., 2003).
When mining ceases and no mitigation is done to rehabilitate the mined area, the
environment and ecosystem are negatively affected by elevated metal
concentration and low pH because the exposure of sulphide minerals in waste
rocks or stockpiles exposed to climatic conditions accelerates acidity which causes
metals in these minerals to dissolve consequently, in open shafts and audits
oxidising conditions are dominated by water may infiltrate or oxygen as
ventilations do not work anymore this is favourable to weathering of pyrite and
sulphide minerals these activities produce Acid Mine Drainage (Lghoul et al.,
2014; Younger, 2000c).
19

Water discharging from mine workings and sites surrounding the mine working has
been seen to have degraded quality because they have in contact with pyrite and
sulphide-rich rocks or waste rocks at favourable conditions for oxidizing minerals
(Younger, 2000c) the water drainage from such will contain elevated levels of
dissolved metals and sulphate.
Weathering depends mainly on the conditions such as how much oxygen and
water is available, temperature and in other cases the amount of dissolved ferric
iron regenerated, this can be seen in the weathering of galena in the atmosphere
which will release lead oxides and lead hydroxide and when galena is weathered
in an aqueous environment at surface it will form lead carbonates and lead
sulphide which may be discharged into aquatic environment.
Weathering can be physical, chemical or/and biological. Physical weathering
composes of a mechanical process which fragments rock into smaller particles by
temperature or erosion rock material is then exposed to chemical weathering
which occurs when the rock material comes into contact with water especially
acidic water and gases in the atmosphere, however; biological weathering is when
bacteria eat on the rock material these bacteria are catalysts in weathering
(Andrews et al., 2013).
Pyrite and other sulphide related minerals weathering is considered as chemical
weathering which involves oxidation of the minerals, this occurs as a result of
decomposition of reductive material as free oxygen is used and the process can
be enhanced by bacterial activities. furthermore, protons and trace elements are
20

emitted into the environment and degrade the quality of water (Andrews et al.,
2013; Ramos Arroyo et al., 2007).
According to White (2013) oxidation is vital in geochemistry because most
elements when in nature they have more than one valance and this influences the
geochemical behaviour of these elements such as iron.
Iron is known to be the most abundant element in the earth’s crust (Albarède,
2003). Iron is commonly a contaminant of mine water discharge which occurs in
both acidic and circum-neutral pH (Holmes et al., 2000; Younger, 2000a) Pyrite is
known as “fools gold” iron sulphide with a chemical formula (FeS2).
The common sulphide minerals that produce acid are marcasite, chalcopyrite,
pyrrhotite and pyrite when weathered these minerals transfers electrons (Valente
et al., 2009). When metal dissolves from primary acid-forming minerals, secondary
sources of acid production are formed this process is naturally (Bowell et al.,
2000). Secondary minerals which are formed when pyrite is weathered are
goethite, ferrihydrite, schwertmannite, hematite and jarosite the formation is
dependent on the geochemistry of the mine water.
There are a few steps involved in pyrite weathering and they are known to be vital
to the end of the process the first one is the oxidation of Sulphur, followed by
ferrous iron being oxidized finally the precipitation and hydrolysis of ferric
compound minerals take place (Dold, 2010).
21

Figure 2.4: Pyrite oxidation simplified diagram showing reaction pathway (from
Banks et al., 1997).
Weathering of iron disulphide pyrite occurs in equation 6 – 9 (Bowell et al., 2000).
The oxidation of pyrite increases iron and sulphide concentration when the ferrous
iron is further oxidized it form ochre this lies on river beds causing a detrimental
effect on the ecosystem of the river (Banks et al., 2001).
When ferric iron is oxidized from ferrous iron it can precipitate from the solution
forming ferrihydrite when the pH is nit low enough to maintain the ionic form, this
precipitation happens in form of either goethite or ferric hydroxides (Belzile et al.,
2004).
FeS2 + H2O + 7/2O2 → Fe2+ + 2SO4– + 2H+ (6a)
22

2FeS2 +7O2 + 2H2O → 2FeSO4 +2H2SO4 (6b)
Fe2+ + H2O + O2 → Fe(OH)3 + 2H+ (7a)
2FeSO4 +H2SO4 + 1/2O2 → Fe2(SO4)3 + H2O (7b)
Fe2+ + 1/4O2 +H+ → Fe3+ + 1/4H2O (8)
FeS2 +14Fe3+ + 8H2O → 15Fe2+ +2SO42- +16H+ (9)
In their study (Bowell et al., 2000) showed how the reactions of pyrite weathering
take place in phases and what it involves. It can be seen in the equations that the
most important aspect is the presence of oxygen.
Phase 1
Equation 6(a) occurs in an abiotic environment and is enhanced by bacterial
oxidation especially equation 6(b).
Equation 7(a) also occurs in an abiotic environment, it becomes slow as pH drops
to 4.5 which it elevates sulphate concentration and decreases iron and drops pH
again equation 7(b)is associated with bacterial oxidation.
Phase 2
Equation 6(a) and 6(b) continues in an abiotic environment and is still enhanced
by bacterial oxidation
23

Equation 7(a) and 7(b) continues at frequency that is determined mainly by action
of bacteria such as T.ferrooxidans At this phase, the adequate pH is lower than
2.5 in this phase again the iron and sulphate concentrations are elevated and the
ratio of ferrous to ferric iron is low
Phase 3
Equation 8 occurs at a speed that is controlled by activity of T.ferrooxidans
Equation 9 will occur at a rate controlled by the speed of equation 8, however, the
favourable conditions for this reaction are pH lower than 2.5, resulting in high
concentrations of sulphate and total iron including a high ratio of ferrous/ferric.
According to (Aykol et al., 2003) oxidation of pyrite disulphide which is a major
source of AMD, it is not the only acid forming process, there is a need for oxidation
of ferrous iron and hydrolysis of ferric iron to further increase the acid formation
(Holmes et al., 2000).
Second, to pyrite, pyrrhotite is the commonly known iron sulphide mineral.
Pyrrhotite instigate in waste from sulphide ores and it is associated with galena,
pyrite and chalcopyrite, publications on weathering of pyrrhotite are rare however
the production of acidity is similar to that of pyrite (Dold, 2010). It is common in
mafic and volcanic rocks, it is a non – stoichiometric composition x which can be 0
or 0.125 an iron lattice valance, commercially the pyrrhotite ore is found in copper
and nickel deposits in countries like Canada, Australia, Russia and China (Belzile
et al., 2004).
24

Dold (2010) in his study showed that weathering of pyrrhotite is similar to that of
pyrite and it can be expressed as equation 10.
Fe(1-x)S + (2-x/2)O2 + xH2O → (1-x)Fe2+ + SO42- + 2xH+ (10)
The oxidation agent in the oxidation of pyrrhotite can be ferric iron (equation 11)
which was formed in pyrite oxidation this is because oxygen is not the only oxidant
this is seen when microorganisms at a later stage oxidize pyrrhotite producing acid
consuming products (Belzile et al., 2004).
Fe(1-x)S + (8-2x)Fe3+ + 4H2O → (9 – 3x)Fe2+ + SO42- + 8H+ (11)
This process proceeds in an acidic environment in the presence of elevated ferric
iron concentration, because under this environmental condition ferric ions remain
in solution and behave as an oxidizing agent for as long as the pH is acidic
producing ferrous iron, sulphate and hydrogen ions (Belzile et al., 2004).
In acidic environment pyrrhotite is known to dissolve at a fast rate the main
products are ferric iron and hydrogen sulphide, however the dissolution can be
slow in moderate conditions causing slow production of iron with little or no
generation of hydrogen sulphide in anoxic environment this is known as a non-
oxidative process (Belzile et al., 2004).
Another iron sulphide mineral which produces acidity in water is chalcopyrite and
the oxidation may be written as equation 12 although this shows no production of
hydrogen ions the acidity production can be seen when the ferrous ion is oxidized
25

and there is hydrolysis of ferrihydrite equation 13 (Dold, 2010).
2CuFeS2 + 4O2 → 2Cu2+ + Fe2+ + SO42- (12)
2CuFeS2 + 17/2O2 + 5H2O → 2Cu2+ + 2Fe(OH)3 + 4SO42- + 4H+ (13)
Chalcopyrite is non sensitive to oxidation, the rate of oxidation is enhanced by the
presence of ferric iron (Dold, 2010).
Iron Sulphide mineral such as arsenopyrite is associated with gold in many cases
arsenopyrite is mined and gold is extracted from arsenopyrite, however, the
oxidation occurs during weathering processes and under reducing conditions
arsenopyrite is found to be stable (Corkhill et al., 2009). When FeAsS is oxidized
sulphate and arsenic are produced, it has been seen in some studies that the
degree of oxidation is more rapidly than that of pyrite, galena, chalcopyrite and
sphalerite (Blowes et al., 2003).
Arsenopyrite is oxidized according to equation 14 when the reaction occurs at the
same time as the oxidation of ferrous iron which leads to the precipitation of
ferrihydrite it is expressed as equation 15 (Dold, 2010). The process for the
oxidation of arsenopyrite is the same to that of pyrite however it is slower when the
oxidant is oxygen (Dold, 2010).
4FeAsS + 13O2 + 6H2O → 4Fe2+ + 4SO42- + 4H2AsO4- + 4H+ (14)
FeAsS + 7/2O2 + 6H2O → Fe(OH)3 + SO42- + H2AsO4- + 3H+ (15)
26

Marcasite chemical formula mimics that of pyrite also proton generation when
oxidized, the rate at which marcasite is oxidized is faster compared to pyrite
because of the large surface area of the fine grain size (Dold, 2010).
The above reactions of weathering are the main producers of acid mine drainage,
the contamination of water resources is not only limited to sulphide and
protonation but the dissolution of other minerals in acidic conditions which are
found when the weathering of iron sulphide minerals proceeds.
27

2.2 STRATIFICATION
2.2.1 Stratification in lakes
The hydrodynamics of lakes are controlled by nutrients and heat, the
understanding of these hydrodynamics processes assist in water quality
management of water resources (Elçi, 2008). Stratification of lakes can be
chemical or thermal and it is commonly distributed in the summer season and it is
established by vertical profiling (Yu et al., 2010).
The most important factors in Lake Ecosystem are temperature and oxygen, the
change in temperature has substantial influence in the biochemical processes
which takes place in the lake (Antonopoulos et al., 2003). It is known that the
dissolved substances and oxygen in the lake ecosystem are controlled by thermal
stratification this happens when there is cooling or heating of water, a density
profile that is vertically stable can be observed when there is a change in
temperature there will be mixing of the two layers epilimnion and hypolimnion
(Read et al., 2011)
In summer the upper layer is less dense it floats above the dense cooler bottom
layer this is because the epilimnion is heated, when there is a temperature
difference between the two layers they remain stratified thermally Figure 2.5 (Elçi,
2008). Furthermore, the chemical and biological properties of these layers are
different in the upper layer, photosynthesis takes place, and there is high dissolved
oxygen concentration as algae, however, the bottom layer decomposition by
28

microorganisms which feed on organic matter reduces the percentage of dissolved
oxygen, the sediments at the bottom of the lake or stream exchange chemical
species with the hypolimnion layer (Çalışkan et al., 2009).
In autumn epilimnion cools down the decrease in temperature results in the
metalimnion disappears as the two layers mix forming one hydrological body, in
this case, the chemical and physical properties remain the same this increases the
biological activity and leads to disturbance in the ecosystem function of the lake or
stream (Manahan, 2010). The above statement shows that the feeding for fish
may be limited causing them to migrate because of nutrients, light accessibility
and microbial materials used by microorganisms disturb the vertical stable density
(Read et al., 2011).
Figure 2.5: Stratification of lakes (from UFI, 1994)
Stratification can proceed for a limited time period or carry on for a longer time it
depends on the time scale it can hours or years, there is decomposition of
materials in which proceed as a result of mixture mechanisms (Read et al., 2011).
The consideration of temperature change with respect to change in depth has
29

been used to determine lake dynamics through the thermocline a barrier between
epilimnion and hypolimnion layers (Read et al., 2011).
Pit lakes are formed when mine voids are flooded, in countries like USA they are
called pools while in Scotland they are ponds or basins. In their study of pit lakes
stratification showed that the ponds at the abandoned Frances Colliery in Scotland
were chemically stratified with good water above as well as poorer water at the
bottom. Waters of the mine are affected by the same geochemistry therefore,
suggests that the shafts should not be considered separately but as mine pools
because of the similarity of water quality properties (Elliot et al., 2007).
Pit lakes may have two layers and as natural lakes the barrier is known as
chemocline while the upper layer is referred to as mixolimnion and
monomolimnion the bottom layer, at the Iberian Pyrite Belt showed a permanent
stratification with high oxygen concentration in the upper less dense layer while
the bottom dense layer, anaerobic layer is separated by the chemocline the lake
does not allow for mixology (España et al., 2009).
The stratification of the mixolimnion is seen by the change in gradient which
illustrates the change in physical and chemical properties in respect to depth
however, the monomolimnion is can have no changing gradient or can be stratified
with a steep gradient change as the mixolimnion layer (España et al., 2009).
España et al. (2009) in their study of the Cueva de la Mora pit lakes observed
stratification in which there was an increase in temperature and electrical
30

conductivity Figure 2.6 the upper layer is about 10 m and the bottom layer at a
depth of 40 m. The temperature profile is uniform 17 and 18 °C at the bottom layer
while the upper layer was stratified sharply. According to the specific conductivity
profile was stratified with a sharp gradient in both the bottom and upper layer from
conductivity of 2 to 12 m S/cm. The result of the stratified pit lakes in Cueva de la
Mora showed that the upper layer had better water quality than the bottom layer
with elevated sulphide concentrations (España et al., 2009).
Figure 2.6: Temperature and specific conductivity profile of Cueva de la Mora Pit Lake
(from España et al., 2009).
2.2.2 Stratification of underground mines
The stratification of underground mines is similar to that of lakes or pit lakes in the
sense that there is density difference within the layers, (Nuttall et al., 2004)
describes how stratification in underground mines is formed and how it can be
disturbed Figure 2.7. When the mine voids filled up as the water table rebound
31

takes place, the water in the shaft rises to a level below the adit and the water in
the shafts becomes stratified, with the upper water with better quality overlying the
bottom poor quality water. The recharging continues and more water flows into the
shafts from the adits causing turbulent flow and disturbs the stratification because
the mine water flowing into the may have different chemical composition to that in
the stratified shaft however, re-stratification can be expected as the shaft is
flooded and the water settles, the flow becomes laminar again the steadiness in
the shafts allows different densities to be observed (Nuttall et al., 2004).
Figure 2.7: Development of stratification in mine water in a shaft and how it is lost (from
Nuttall et al., 2004)
Wolkersdorfer (2008) provided a detailed description of stratification in flooded
underground mines. Stratification happens when the physical and chemical
properties of water profile in the horizontal layer are different. Stratification is a
phenomenon of both coal and metal mines in which there is a change in water
quality parameters occurred with increasing depth.
32

Stratification of mine water provides chemical properties such as electrical
conductivity and thermodynamic which can be measured as temperature changes
with depth. Stratification has been known as a method of mine water remediation
because it assists on the understanding of the physical profile of mine water strata
(Wolkersdorfer, 2008). The density of water is dependent on temperature,
pressure and chemistry composition (Dietz et al., 2012). Physical properties such
as viscosity, temperature and density when they change physical and chemical
characteristics of the different horizontal layers (Wolkersdorfer, 2008). The mine
water in shaft 2 of Jindrich density was influenced by elevated metal concentration
and increased pressure this caused mine water to be steady with stratified layers
(Johnson and Younger, 2008).
According to (Wolkersdorfer, 2008) stratification of flooded mines has been
studied worldwide in Germany, USA, UK, Austria and Africa. Mine water can be
stratified for years and may not be affected by (Zeman et al., 2008). Stratification
profile in the abandoned Frances colliery which showed temperature and EC
profiling stratified mine water was evident from better water quality overlying poor
water quality Nuttall et al. (2004). The Frazer’s Grove mine showed elevated
concentration of iron, sulphate and zinc thus the mine water was acidic as a result
the conductivity ranged between 500-3200 μS/cm Figure 2.8 stratified mine water
was evident seen from the low pH in the lower parts of the mine and a
circumneutral pH at the upper parts of the mine water (Johnson et al., 2002).
33

Figure 2.8: Conductivity and temperature log of No. 2 Shaft at Frazer's Grove Mine (from
Johnson et al., 2002)
A study conducted in Oklahoma, USA at the Picher Mining District whereby galena
and sphalerite were mined. The mine was about 200 m deep and known to be the
largest lead and zinc mine fields. The pH of the mine water was between 4 and 5.
The stratification study showed that there was no connection among the upper and
lower layers however a connection was found between shafts hydraulically as
seen by the similarity of temperature and electrical conductivity in different shafts
and depth (Wolkersdorfer, 2006). Other studies such as the one conducted in
Pennsylvania Anthracite Fields showed an EC profile increase with depth from 400
-1000 μS/cm in shallow parts of the mine while in deeper parts of the mine EC
increased from 1000- 1400 μS/cm, the deeper parts of the mine has slow-moving
subsystems with poor water quality (Coldewey et al., 1994).
34

2.3 MINE WATER AND GROUNDWATER AQUIFER
2.3.1 Characteristics of mine water aquifers and mine pools
A characterization of the volume of groundwater which accumulates in the
cessation of underground mine is known as mine pool, an aquifer is defined by
means of a “geological unit that can store and transmit water at rates fast enough
to supply to a borehole” aquifers are heterogenic and their thickness are different
in distance over many meters. (Feeley III et al., 2003; Fetter, 2000; Yao et al.,
2016). Man-made aquifers which are created during mining operations are the
sources of Acid Mine Drainage which is caused by exposed surface areas through
which water flows in a permeable media by interconnected shafts and audits
(Cánovas et al., 2016). Historically groundwater movement and transportation of
solutes in aquifers has received attention from engineers and geoscientists for a
clear understanding of these systems (Abdelaziz et al., 2015).
The interest in aquifers has led to characterization of aquifers worldwide, such as
in the study of Vías et al. (2010) in Europe that mapped carbonate aquifers to
analyze their vulnerability and the study of Abiye (2010) in East Africa which
mapped the transboundary aquifers characterizing the recharge conditions and
nature of host rocks. When it comes to aquifers in Africa there is less information
especially on basement aquifers which are fractured and weathered in the Karoo
also the shales which are found in West of Africa consequently, characterization of
aquifers assist hydrologists to effectively protect subsurface water as a resource of
economic value (Robins et al., 2007).
35

Abiye (2010) demonstrated that aquifers may be shared among countries such as
aquifers of Ethiopia–Eritrea; Kenya; Sudan; Somalia; Djibouti. Carbonate rocks
dominate Ethiopia-Somalia shared aquifers they have characteristics of dissolved
cavities and high water supply from their fractured features. The aquifer of
Ethiopia–Eritrea comprises of limestones and sandstones with a great possibility
of groundwater production in contrast the Ethiopian- Kenya shared aquifer is made
up of basaltic rocks that are fractured with multi-layer aquifer whereas lithology of
Ethiopia–Sudan comprises of greenschists, ultramafic and marble rocks
interconnected with volcanic rocks, alluvial deposits and sedimentary rocks.
Beneath sedimentary rocks lies volcanic rocks which are fractured and weathered
acting as the main groundwater supply, the source of groundwater in Ethiopia–
Djibouti aquifers is controlled by alluvial and volcanic aquifers main rocks are
basalts, siliceous and chorora characterized by intensive fracturing (Abiye, 2010).
In South Africa the Karoo Supergroup covers about 50% of the geographical area
and it is regarded as the largest groundwater supply of the arid and semi-arid
zones in the country. The aforementioned comprises of weathered semi-confined,
unconfined shallow aquifers and fractured semi-confined and confined deep
aquifer systems. Other aquifers in South Africa include those found in Transvaal
Supergroup (dolomitec aquicludes), Ventersdorp Supergroup (ventersdorp lavas)
and Witwatersrand Supergroup (confined fractured aquifer) (Botha et al., 2004;
Witthüser et al., 2015). Four major provinces in South Africa are supplied by the
karstic dolomitic aquifers of the Malmani Formation of the Transvaal Supergroup,
the aquifer encompasses more water than the Vaal Dam (Durand, 2012).
36

However the aquifers found in the Karoo formations supply water irregularly the
reason behind this is the formation features (compact rocks and water storage
occurs on perpendicular fractures) subsequently these properties serve as flow
pathways the fractured hard rocks make borehole drilling difficult even so many of
the South African towns are situated in such aquifers such as in Dalmas,
Mpumalanga receives its water supply from karstic dolomitic aquifers (Botha et al.,
2004; Robins et al., 2007).
Fractured aquifers are common in metamorphic and igneous rocks found in
shared aquifers of Ethiopia-Somalia. The heterogenetic properties govern the
movement of groundwater and hydraulic conductivity and these aquifers possess
different features such as flow of groundwater predominantly taking place in the
fractured zones, unconnected groundwater movement paths and channeled
groundwater movement (Abdelaziz et al., 2015; Abiye, 2010). Volcanic and alluvial
aquifers are common in metamorphic rocks characterized by weathered features
and manifestation of water in lower depth such aquifers are shared in Ethiopia-
Djibouti regions (Abiye, 2010).
Karst aquifers are categorized by effective groundwater drainage resulting from
the development of caves different hydraulic properties and large voids. Major rock
hosts for karst aquifers are dolomite, gypsum, quartzite and anhydrite (Kaufmann,
2016). The dissolution of these host rocks by acidic water forms cavities leading to
the change in porosity and hydraulic conductivity of the aquifer system as the host
rocks become more fractured (Kaufmann, 2016; Wolkersdorfer, 2008).
37

Crystalline aquifers allow secondary permeability through deformation and faulting
in marble layers. The rate of rainfall substantially influences the water supply of
crystalline aquifers, lower rainfall consequently lead to little or no water quantity
(Abiye, 2010).
2.3.2 Aquifer parameters
In hydrological studies of fractured rocks it is important to predict the flow
contamination transfer in heterogeneous systems (Le Borgne et al 2007).
Hydraulic conductivity is directly proportional to grain size in a porous media
(Odong, 2013). Understanding it is important in water flow as it controls mobility of
pollutant transportation.
Geological structures and geomorphology determines the occurrence of
groundwater including the availability of recharge sources. Hydraulic parameters
control the movement and storage of water. The factors that control migration of
pollutants include the chemical and physical properties of contaminants further
affected by properties if soil and aquifer. The properties of soil and aquifer are
directly proportional to hydraulic parameters (Hiscock, 2005). Change in
permeability causes permanent effects such as depressed water level, change
discharge (Booth, 2005).
Hydraulic conductivity is the measure of the ability of a porous medium to transmit
under a hydraulic gradient. It controls the velocity of groundwater flow which
controls the velocity of pollutant flow through the aquifer. High conductivity equals
38

increased susceptibility to contamination (Hasiniaina et al., 2010) The measure in
which water can move in a horizontal direction through the thick aquifer is known
as transmissivity. In a permeable rock water which is released defines the
storativity of the aquifer. When there is saturation of the volume of water that is
stored or released from pores resulting from mineral compression (Fetter, 2000).
Dolomite aquifers found in Witwatersrand, Vereeniging and Pretoria consists of
weathered rocks characterized by high storage, transmissivity and permeability
and low water levels (Buttrick et al., 1993).
A study conducted by Schrader et al 2014 in far west rand, Johannesburg, South
Africa illustrated the deeper we go down a dolomite rock dominated aquifer a
decrease in storativity Figure 2.9. Water storativity by aquifer depends on
fracturing and depth. Underneath the water table 40 m below surface it was
observed that the percentage of storativity is high at 10% because there is more
fractures (more open spaces in which water way me stored) but as we go down
the karst where weathering is weak and no fractures just faults storativity becomes
less with a percentage of 0.02 %.
39

Figure 2.9: Schematic depiction of the vertical zonation of the dolomite in the FWR based
on the degree of karstification/ fracturing and storativity (according to Winde et al. (2006)
Barns, 2015 concluded that properties of aquifers such as hydraulic conductivity
and porosity define the flowing path for groundwater whereas mobility of solutes
resulting in pathway of contaminates depends on dispersivity.
Brassington, 2007 provided a detailed description of the properties of an aquifer
characteristics (a) hydraulic conductivity is defined as the volume of water that will
flow through an aquifer in a unit time. (b) Permeability is a determinate of the rate
at which water can flow through an aquifer (c) Porosity a measure of how much
water is contained in an aquifer (the proportion of the volume of rock that consist
of pores of the total rock mass. It is controlled by grain size, shape, degree of
sorting, extent of chemical cementation and amount of fracturing). It does not
provide a direct measure of the amount of water that will drain out of the aquifer
because some of the waiter remains in the rock. A term used to define
groundwater that drains out of the aquifer is specific yield (d) desp ersivity is a
40

term commonly used to describe a manner in which water is dispersed as it flows
throw an aquifer. (e) Storativity is the total volume of water in an aquifer. (f)
Transmissivity
The subsequent groundwater stream example is not just controlled by the
arrangement of the water table additionally by the dispersion of hydraulic
conductivity in the rocks (Sophocleous, 2002)
Stream frameworks rely on upon both the hydrogeologic qualities of the rock and
soil material. Zones of high penetrability in the subsurface capacity as channels,
which cause improved descending slopes in the material overlying the upgradient
part of the high-porousness zone (Sophocleous, 2002).
2.3.3 Interaction of mine water and groundwater
The understanding of the interaction between groundwater and surface water is
vital especially in areas where drought is predominating and the flow acidic mine
water discharges in to rivers and streams (Nordstrom, 2011).
Water in a region stream framework streams to a close-by release region, for
example, a lake or stream. Water in a provincial stream framework ventures a
more noteworthy separation than the area stream structure, and regularly releases
to important waterways, important lakes, or to seas. A moderate stream structure
is described by one or more topographic highs and lows situated between its
energize and release zones (Sophocleous, 2002)
41

Groundwater moves along stream ways that are sorted out in space and frame a
stream framework (Sophocleous, 2002). The collaborations of streams, lakes, and
wetlands with groundwater are administered by the positions of the water bodies
with admiration to groundwater stream frameworks, geologic attributes of their
beds, and their climatic settings (Sophocleous, 2002)
The spatial circulation of stream frameworks additionally impacts the force of
common groundwater release. Water catchment may acquire groundwater from
the region rapidly inside the closest topographic high and potentially from more far
off territories (Sophocleous, 2002)
As the mine voids turn out to be full to flooding, the exceedingly sullied
groundwater can relocate into connecting aquifers or into surface waterways,
where nonetheless devastating resource. Degrading the ecosystem (Younger,
2000c)
water that refills the mine breaks down any acidic salts that have developed on the
pore spaces of the uncovered dividers and roofs of underground loads, this
underlying seepage water has a tendency to be all the more conceivably
contaminating (Johnson et al., 2005)
42

2.4 TRACERS AND TRACER TESTS IN UNDERGROUND MINES
2.4.1 Types of tracers
The term tracer is defined as a substance introduced into a biological system or
any other system so it is consequently be distributed and it could be identified from
its colour, radioactivity or its unique properties. Tracers in hydrology are aimed at
validating, testing and developing proper hydrological system representations that
present information by using environmental and artificial tracers (Leibundgut et al.,
2011). Environmental tracers are understood as intrinsic constituents of water
cycle, they are naturally occurring however, in some cases they can be
accidentally introduced for hydrogeological investigations. Tracers that are known
to be artificial are defined as substances that are introduced into a hydrological
system that is being investigated (Leibundgut et al., 2011).
In a natural environment, tracers are used to mark patterns especially for wildlife in
territorial identification at very low concentrations, in this case, data can be
collected and characterization of substances achieved. Nonetheless, tracers in
hydrogeology depend on the study purpose tracers may be suspended, floating or
dissolved substances (Leibundgut et al., 2011). Artificial tracers aid in
understanding the movement processes in the hydrologic environment and
determining hydraulic parameters and to envision flow paths within a hydrological
system. These tracers are considered as a tool to characterize and understand
difficult flows in the surface, groundwater, soil and aquifers or artificial systems
(Leibundgut et al., 2011). In contrast, environmental tracers are used to
43

understand catchment areas also historical background of water resources and
hydrological data in unmeasured basins, in other cases, the use extends to
integrated hydrological systems that are inaccessible (Leibundgut et al., 2011).
According to their definition environmental tracers are utilized while artificial
tracers are applied. In soils, surface and groundwater environmental tracers
diffuse or precipitate when utilized; they can be used in large areas for longer
timeframes at catchment areas and help in finding solutions for applied problems.
The application of artificial tracers is done in clearly defined hydrological systems
at a known interval and measured tracers mass (Leibundgut et al., 2011). Pollution
tracers are neither artificial or environmental they are present in a hydrological
cycle through human activities such as waste disposals or the release of gaseous
substances into the atmosphere (Leibundgut et al., 2011).
Currently, the two main groups in tracing hydrology are subdivided according to
their properties. Environmental tracers which are considered for scientific studies
are stable isotopes, radioactive isotopes, noble gases, geochemical compounds,
and physio-chemical parameters. Furthermore, artificial tracers that are applied in
hydrological studies are either solute tracers such as fluorescence, non-
fluorescent dyes, salts, fluorobenzoic acids, deuterated water and radionuclides or
dissolved gas tracers and particulate Table 2.1 (Leibundgut et al., 2011).
44

Table 2.1: Tracers used in hydrology
Artificial tracers Environmental tracers
Soluble tracers Non soluble tracers
Fluorescence tracers
Uranine
Napthtionate
Eosine
Rhodamines
Pyranine
Non-Fluorescent dyes
Brilliant Blue
Salts
Potassium iodide
Lithium chloride
Sodium chloride
Sodium bromide
Potassium chloride
Potassium bromide
Sodium borate
Deuterated Water
Fluorobenzoic acids
Radionuclides
Tritium
Bromide-82 (82Br)
Neon
Sulphur hexafluoride
Helium
Krypton
Particulate tracers
Bacteria
DNA
Lycopodium spores
Phytoplankton
Viruses
Synthetic microspheres
Phages
Stable isotopes
Sulphur-34 (34S)
Deuterium (2H)
Nitrogen-15 (15N)
Oxygen-18 (18O)
Carbon-13 (13C)
Radioactive isotopes
Argon-39 (39Ar)
Chlorine-36 (36Cl)
Tritium (3H)
Krypton-85 (85Kr)
Carbon-14 (14C)
Radon-222 (222Rn)
Silicium-32 (32Si)
Radium- 226 (226Ra)
Geochemical compounds
Heavy metals, silicate,
chloride
Noble gases
Physio-chemical
parameters
Temperature, Electrical
conductivity
Pollution tracers
Boron, SF6, nitrate, CFCs, radioactive compounds and phosphate
45

Environmental tracers are mainly used to (i) identify genesis and water
components; this is the most cases provision of recharge elevation, volume and
the distinction between summer and winter recharges and carbon dissolution. (ii)
research hydrologic systems; the discovery of runoff constituents, groundwater
movement, recharge, direct or indirect channels and water balances of lakes. (iii)
measure flow constituents; evaluation of evaporation from rivers, lakes and seas,
mapping surface waters. (iv) residence time confirmation; calculate carbon date
and water movement timeframe (Leibundgut et al., 2011).
The use of environmental tracers is restricted by the technique analysis ability and
competence of tracer method and time (Leibundgut et al., 2011). The main
advantage of using environmental tracers is their natural occurrence. These
tracers can be used for local or global hydraulic investigations also be used as a
tool for geological antiquity, precipitation origination or recharge and subsurface
flow. The use of environmental tracers in any space and time allows their
integration to give them a distinctive quality (Leibundgut et al., 2011).
Integrated use of artificial and environmental tracers can enhance the success of
tracer application in hydrology. In the planning phase of artificial tracing
environmental tracer methods can be used. Unsuccessful artificial tracer test could
be avoided by assessing primary residence time and analysis of flow prior to
tracing test. Environmental tracers could be utilized as a secondary method for
tracer testing application of artificial tracers and can be used as a control system
when there is no breakthrough curve (Leibundgut et al., 2011).
46

Artificial tracers are used to determine connectivity of hydrological systems,
groundwater flow paths, water movement direction in aquifers and catchments,
confirmation of flow velocities, aquifer hydraulic parameters that emanate from
residence time, breakthrough curve and dispersion (Leibundgut et al., 2011).
The most important artificial tracers are fluorescence tracers. They are commonly
used by hydrologists because of their distinctive properties, easy to handle, highly
sensitivity, simple to analyses, low detection limit and only small amount
necessary for field experiments (Kass et al., 1998). The most important and
commonly used artificial tracers are fluorescence tracers, salt tracers are second
then advanced tracers. However, drifting particle tracers are specialized and only
applied in the assessment of specific investigations such as capacity filtration in
unsaturated zones (Leibundgut et al., 2011). The success of tracing experiment in
both field and laboratory requires an understanding of the characteristics of tracers
and method applied (Leibundgut et al., 2011). Tracers in hydrology are applied to
investigate water within different aspects, attributes in all various elements and
underlying substances in the water cycle.
2.4.2 Salt tracer physical and chemical characteristics
The use of salt as a tracers in hydrological investigations provides satisfactory
results
2.4.3 Interpretation of salt tracer results
47

2.5 EFFECTS OF MINING ON THE WATER ENVIRONMENT
2.5.1 Effects of mining on human health and aquatic life
Many studies have been done to fully understand contamination diffusion from
abandoned mines and their substantial influence on watercourses and the
ecosystem (Palumbo-Roe et al., 2012). Consequently, the receiving water course
must maintain an acceptable ecological status this can be achieved through the
understanding of the effect which mining activities pose on the aquatic ecosystem
through studies (Younger et al., 2004). Watercourses which are affected by mining
activities in many cases experience high iron content this is a result of ferrous iron
oxidation to ferric iron the product is consequently precipitation of ferric hydroxides
on stream beds (Younger et al., 2004).
Benthic invertebrates and algae are mostly affected by elevated precipitates of
ferric hydroxides (Younger et al., 2004). Other factors which contribute to the
degradation of aquatic environment is photosynthesis decline this means that most
primary producers are unable to produce food, therefore, there is an imbalance in
the aquatic ecosystem the bottom feeders are mostly affected as there is an
increase in turbidity resulting from suspended sediments which are discharged
into watercourses (Younger et al., 2004). It has been recorded that abandoned
mines in Europe are the major environmental polluters of soils and rivers near
these abandoned mining sites (Beane et al., 2016). ## Africa and RSA.
These contaminates from the abandoned mines are known as the worst
48

environmental polluters they have a substantial influence on both human well-
being and the ecosystem (Gutiérrez et al., 2016). This has been seen globally
where metal discharging from abandoned mines caused severe degradation to
numerous rivers as compared to agricultural pollutants (Ramani et al., 2014).
When metals and semi-metals exceed the recommended limit they may pose risk
to the well-being of humans (Singh et al., 2008). It is important for the human
population to have access to drinking water that is safe and clean to use for
domestic and recreational purposes (Absalon et al., 2007). These metals and
semi-metals pathways are through water supplies this is how humans ingest these
contaminates (Thornton, 1996).
Zinc is a well-known essential element which helps the body in the production of
enzymes, it supports growth and generation of tissue however when ingested at
elevated concentration it may cause abnormalities in humans(Zhang et al., 2011).
Unlike zinc, lead is a non-essential element and it has a detrimental effect on
humans. In situations where lead recommended limit was exceeded has resulted
in the malfunctioning of the central nervous system and the immune system this
occurs in adults consequently, in children intelligent is reduced and the physical
development is slow and they experience social behavioural problems(Zhang et
al., 2011) (Mackay et al., 2013). The symptoms of excessive dosage of zinc are
vomiting, nausea and stomach cramps this will in long-term cause imbalance in
cholesterol and infertility in both males and females (Zhang et al., 2011).
Nagajyoti et al. (2010) define contamination as any substance in the environment
that causes a change in the condition of the environment by degrading the quality
49

and/or leading to detrimental effects. In South Africa common sulphide metal
mercury is cinnabar which is associated with gold mining. Furthermore, it is ranked
the second world mercury polluter where as china is the first and the emission of
mercury may be from the burning of fossil fuel. The larges spillage of mercury
occurred in Kwa-Zulu Natal were by contamination of the large river Magceni lead
to restriction of fishing in the area to avoid consumption of fish because if fish is
consumed whereby it has inorganic mercury lead to death, loss of sight and
damage to central nervous system (Davies et al., 2010).
The world’s largest producer of manganese is South Africa, it produces 80%.
Manganese is suitable for both humans and animals but if consumed in levels
above the recommended dosage it may be toxic and causes blood clotting, birth
defects and colour change in hair with chronically exposure (Davies et al., 2010).
There was a disease discovered in North West and Northern Cape of South Africa
in sheep and cattle known as geophony it lead to hepatitis and death (Elsenbroek
et al., 2002). Iron in elevated concentration in the body leads to siderosis an
accumulation of iron because when ingested it becomes insoluble in the digestive
system whereby the pH is circum-neutral. In males of Johannesburg South Africa,
high levels were found in their liver at the death when post-mortem was done it
was found that it causes tissue damage because it is the only essential metal
which cannot be excreted out of the human system (Davies et al., 2010).
Fluoride is naturally occurring in ground and surface water at a low concentration
of 0.03 mg/L it is beneficial for teeth in humans but at elevated consumption, it can
be toxic to both animals and humans. In provinces such as KZN, Limpopo, North
50

West and Northern Cape fluoride is predominant because of the usage of
groundwater and surface water for domestic and drinking purposes (Davies et al.,
2010). When there is low magnesium in water it was evident in some parts of
South Africa that there was death caused by ischemic heart disease because
magnesium plays an imported role in energy production and cell migration
including metabolic reaction (Davies et al., 2010).
2.5.2 Consequences of mining on water resources
##
2.5.3 Treatment of polluted mine waters
51

3 METHODOLOGY
3.1 DESCRIPTION OF STUDY AREA
The abandoned Edendale Lead Mine is located on the farm Nooitgedagt 333 JR in
Silverton, Pretoria east Figure 3.10. Their two shafts mined are separated by the
main road R513. The Edendale Lead Mine was one of the earliest mines in the
Transvaal region and operated from 1890 to 1974, producing 6 333 t of ore, 4 762
t of lead, 1 127 t of silver and 105 t of antimony (Glass, 2006).
Figure 3.10: Overview of three shafts of the abandoned Edendale Lead Mine (Google
Earth, 2004 http://earth.google.com; Datum WGS84, geographical coordinates, without
scale).
52

Table 3.2: Coordinates for each of the sample sites
Sample
Name
Location Datum WGS84, geographical
coordinates
E01 Edendale Shaft 1 25° 41’ 2.87 S 28° 26’ 6.68 E
E12 Edendale Shaft 12 25° 45’ 5.03 S 28° 25 33.74 E
E13 Edendale Shaft 13 25° 41’ 4.77 S 28° 25’ 34.33 E
EPD Edendale Point of Discharge 25°41’ 6.32 S 28° 25’ 35.70 E
EUS Edendalespruit Upstream 25° 41’ 12.05 S 28°25’ 40.58 E
EDS Edendalesruit Downstream 25°41’ 6.81 S 28° 25’ 32.27 E
3.1.1 Geological setting and study area
Southern Africa has the largest sedimentary deposits which are found in the
Kanye Basin of Botswana, Transvaal Basin and the Griqualand West Basin these
three basins are found in the Kaapvaal Crayton Figure 3.11 (Eriksson et al.,
1993).The Transvaal Basin is aged between 2.66 to 2.05 billion years is made up
of chemical and clastic sedimentary and some volcanic rocks furthermore, the
lowest part of the basin comprises of quartzite, carbonates and cherts and far west
shales, dolomites and sandstones overlay this basin. The Transvaal basin
comprises of the Rooiberg Group, Pretoria Group, Chuniespoort and the oldest
53

Wolkeberg Group (Eriksson et al., 2012). The study area is located in the Silverton
Formation which is part of the Pretoria Group.
The Pretoria Group is 2100 to 2400 million years of age and is overlying the
Chuniespoort and is overlaid by the Rooiberg Group is made up of shales and
quartzite which are about 6-7 Km thick (Errikson, 2012). The quartzite dominating
the Pretoria Group is a result of metamorphism by the Bushveld Complex intrusion
sandstones. Consequently; Rooiberg Group is made up of lavas which are found
to be metamorphosed into leptites and hornfilses (Eriksson, 2012). The Silverton
Formation of the Pretoria Group is sandwiched between Daspoort and
Magaliesberg Formations. The Daspoort formation which is succeeded by the
Silverton Formation is characterized by iron rocks which are found in the east and
quartzite which are matured in age including secondary mudrocks (Eriksson et al.,
2012). The Magaliesberg Formation a succession of the Silverton Formation is
commonly known as marine sandstone because of the shallow water structure and
the maturity of petrographic nature, it is recognized by the immature sandstone.
The Silverton Formation is aged between 2100 and 2160 million years it
comprises of carbonate mudrocks which are interbedded with sandstones, chert
and dolomite. Upward the basin excessive calcium oxide and manganese oxide
shales including tuff and is collectively known as Lydenberg shale are recognized.
In the eastern part, there is Machadodorp volcanic which consists of basalts it is
shallow and interbedded with carbonate rocks in the basin on the north (Erikson,
2012).
54

Figure 3.11: The three main outcrops of Kaapvaal craton, Kanye basin in Botswana,
Griqualand West basin and the Transvaal basin (from Eriksson et al., 2012).
The common known sedimentary rocks are shales, sandstones and mudrock
mainly found in the Pretoria Group and identified in the Silverton Formation. Lead
is found in galena which occurs in sedimentary rocks and the mineralisation of
lead is measured by faults which were found around the same age as the
occurrence of Bushveld Complex intrusion in Edendale Lead Mine (Glass, 2006).
The abandoned Edendale Lead Mine was dominated by quartzite on the south
which became less on the north. The quartzite found in the two shafts belongs to
55

the Magaliesberg Formation and it was interbedded with limestone and shale. The
limestone was 3 m thick on shaft 1 and the rocks were found to be carbonate
which was altered by shales while the rocks in shaft 2 were of fine grain and
identified as limestone (Glass, 2006). The ore deposits of the abandoned
Edendale Lead Mine produced galena and zinc with chalcopyrite including
sphalerite, shaft two on the north produced with a small quantity of galena which
was less than 1 m in thickness, pyrite and sphalerite. Ore was fine grained this is
an indication of replacement which may have taken place when the incomplete
gangue occurred resulting in the mixture of galena (Willemse et al., 1944)
3.1.2 Climate and hydrology
Pretoria is 1339 m above sea level and is surrounded by Magaliesberg Mountains
these mountains are able to trap warm air rising the temperature found in Pretoria.
The summers are long and wet as more precipitation is received during this
season consequently; the winters are dry and short. The area receives a minimum
of 625 mm and a maximum of 750 mm of rainfall per annum (Glass, 2006).
According to the climate data, the study area has the lowest rain of 7mm in the dry
season (winter) and a peak of rainfall in the wettest and hottest month, January
with 138 mm.
The Roodeplaat dam found in the north-east of Tshwane is the main catchment for
most rivers in Tshwane; it receives water discharging from Edendalespruit,
Moretele River and Pienaars River. Edendalespruit goes through farm
Nooitgedatch and it flows through the Magaliesberg and Leeufontein quartzites it
56

then discharges in the south eastern part of the dam (Glass, 2006).
Groundwater runs from elevated ground into valleys this movement is controlled
by gravity and it depends on porosity of the rocks, the void size and the gradient of
the water table (Lurie, 1981) The shales found in the study area forms part of
South African boreholes according to South African borehole information, Silverton
Formation yields between 72 and 120 000 L/day in most boreholes with 26 m to 29
m depth with no failure percentage (Lurie, 1981).
3.1.3 Mining history
The currently known abandoned Edendale Lead Mine which is situated on farm
Nooitgedagt 333 JR east of Tswhane, Silverton operated from 1900 to 1974, in the
1800 prospecting was done the previous plans are not available however only 3
shafts of the mine remain, one on the south of the R513 road and the other two
shafts are in the north east of the road. Consequently, the mine was owed by
various companies and it operated by the name of the company at the time of
ownership Table 3.3. The first mine was the shaft 1 which was mined in 1900 it
was a smelter plant this is evident by the structures which were found on the farm.
In 1904 the mining depth was increased at shaft 1 by 41 m and the opposite mine
was at 61 m Figure 3.12 the mine produced 11000 tons of ore in that period which
produced 80 % of galena and 450 g of silver the second shaft was further mined to
212 m in 1905 and 1120 tons of lead ore was produced (Reeks, 2012).
The increase in mining depth resulted in water inflow into the mine this required
57

massive pumping which allowed the mine to sell millions of litres to other mines
monthly. Consequently, the mine on the north east of the road also had an
increased mining depth from 45 m to 94 m then later to 184 m this happened in
1906 and during this mining period the primary vein was galena and cerrusite
there was also argentiferous zinc which increased in production percentage. The
mine at this time was the first mine to produce ore and directly smelt it at the same
site this was in 1906–1907 (Reeks, 2012).
Table 3.3: Names used at the Edendale mine during operation (modified from Reeks,
2012)
Company name/ mine name Operating years
Edendale Lead Mines Syndicate Ltd 1894 – 1905
Edendale Estates Ltd 1903 – 1909
Donerhoycul Tributing Syndicate Ltd 1911 – 1914
Edendale Inspection Syndicate 1918 – 1919
Edendale Developing Syndicate Ltd 1920 – 1923
The Edendale Lead and Zinc Co Ltd 1935 – 1937
Union Lead Mine 1937 – 1938
58

Union Lead and Silver Mine 1938 – 1941
Edendale Lead Mines (Pty) Ltd 1949 – 1974
Figure 3.12: Cross section of the Edendale No 1 Mine 1903 – 1909 (From Reeks, 2012)
In 1908 the Edendale mine was liquidated then closed. However, in 1912 it was
reopened and during the operation, 176 tons of lead ore was produced including
an unknown quantity of zinc ore with 35 kg of silver (Reeks, 2012). Furthermore, in
1920 first grade lead and silver were produced from the ore deposit embedded
fissure which was 1,5 m in width (Reeks, 2012).
A third shaft was opened in 1921 it connected east of the second shaft and it was
17 m in depth it was further extended to 36 m beneath the cerussite vein which
was 46 cm and produced first grade galena, westwards of the third shaft a
59

connecting shaft was also open it was 54 m initially and it was sunk to 214 m the
mined vein produced 40 tons of ore yearly (Reeks, 2012).
The mine was closed in 1923 due to financial restraints and reopened under
Edendale Lead Mines in 1928 to 1931 however, no mining reports were found for
this duration only prospection plans (Reeks, 2012). The mine operated as
Edendale Lead and Zinc Mining Co from 1935 to 1937 in this time again only
development plans were made hence there are no records of production (Reeks,
2012). Furthermore, the only production recorded was in 1937 when Union Lead
Mine was the new operating mine name producing 65 tons of lead and in 1938 the
new mine name was Union Silver and Lead Mines it increased the production of
lead to 88 tons plans and development were done Figure 3.13, it was reported that
during the operation the mine was a smelter however, the smelting process was
unsuccessful therefore, a sintering process was made from the reverberatory
furnace that produced 2.5 tons of lead daily from 1938 to 1941 there were no
records after this time (Reeks, 2012).
60

Figure 3.13 Cross section of the Edendale (Union Silver and Lead Ltd) No 2 Mine 1937
(from Reeks, 2012)
When mining ceased in 1941, there are no records of mining activities or
production from 1942 to 1974 when the mine was operating under Edendale Lead
Mine and the only reports are the fines for late tax submissions and the mine was
dissolved in 1974 (Reeks, 2012). The lifespan of the mine was 70 years and there
was 5000 tons of lead and 1110 kg of silver which was produced in the duration
from 1890- 1941 (Reeks, 2012).
There were infrastructure foundation found in the year 2010, three shafts
remaining one on the south of the R513 which was Edendale mine No. 1 and it is
7 m in depth for the purpose of the study it is known as shaft 1 and the other two
on the north east of the main road which was Edendale mine No. 2 the shafts are
7 m and 4 m respectively they are known as shaft 12 and shaft 13 for the purpose
of this study. The shafts were numbered by the Council of Geoscience and not
according to the historic mine plans.
61

3.2 DATA COLLECTION
In order to characterize the mine water quality of the abandoned Edendale Lead
Mine, 16 water samples were collected from different sample locations Error:
Reference source not found. For this study water samples were collected at shaft
1, 12 and 13, Edendale point of discharge and Edendalespruit both at the
upstream and downstream. In order to better understand nature, potential pollution
and hydrodynamic processes of the mine water at the abandoned Edendale Lead
Mine sampling, stratification and tracer test were done in both dry and wet
seasons at different sample localities.
3.2.1 Mine water chemistry
The on-site parameters such as pH, temperature, oxygen content, electrical
conductivity, redox potential and alkalinity (kS) of the mine water were measured
on-site with a portable instrument at every sampling location Table 3.4:
Instruments used to measure on-site parameters in the field. The measurements
of on-site parameters were of importance because the physical and chemical
properties of mine water can change rapidly. Therefore the on-site parameters can
never be constant. We measured the alkalinity of the mine water by titration. We
used 50 mL of the sample and added a strong acid (H2SO4) by a digital titration
and we continually measured the pH to the end point of 4,3. The data was used to
calculate the acid capacity of the mine water.
62

Table 3.4: Instruments used to measure on-site parameters in the field
Parameter Measurement Instrument
Temperature, pH, Electrical
Conductivity, Redox potential
Hach or Myron L Ultrameter
Dissolved Oxygen Hach Oxygen sensor
Acid Capacity Hach Digital Titration kit
3.2.2 Sample collection procedures
Samples were collected in pre-cleaned and pre-contaminated 500 mL and 50 mL
polyethene bottles from shaft E01, E12, E13, Edendale Point of Discharge (EPD),
Edendalespruit up-stream (EUS) and Edendalespruit down-stream (EDS). All
bottles were labelled with the sample location, date and sample name and were
stored at 4°C temperature in a dark cooler box container and were transported to
the laboratory for analysis.
To collect samples in the shafts a bomb sampler was made. The bomb sampler is
made of the bottom of a cut 1.5 L of a plastic water bottle attached to a stone on
the side and tied to a rope which was about 10 m in length. The bomb sampler
was lowered down each shaft (E01, E12, and E13) to a certain depth when it was
filled with water the rope was slowly pulled up lifting the sampler to the ground
surface. The sampler was rinsed 3 times with the sample water and the 500 mL
63

bottles were also rinsed 3 times with sample water the procedure for lowering the
sampler down the shaft was repeated several times each time a water sample was
collected.
The sample water was then transferred into 500 mL bottles which were filled to the
top and placed into the cooler box which had blue iced bottles for each sample
location shaft E01, E12 and E13. Furthermore, the water sample was transferred
to a 500 mL jag and a 50 mL syringe was rinsed with the sample water a 0.45 μm
membrane filter was attached to the syringe and was used to draw sample water
from the jag and rinsed the 50 mL bottle 3 times then water was transferred using
the syringe attached to the filter into the 50 mL bottles the samples were acidified
nitric acid and were also stored in the cooler box with blue ice bottles and
transported to the laboratory.
Sample water was transferred into a 500 mL plastic jag which was also rinsed 3
times with the sample water at each shaft (E01, E12 and E13) and on-site
parameters (pH, DO, temperature, EC and redox) were measured and data were
recorded in the field book.
Other water samples were collected from the Edendalespruit at EUS and EDS.
The stream was shallow water samples were collected using 500 mL and 50 mL
plastic bottles. The 500 mL plastic bottles were immersed in the stream in an
upstream position collecting sample water to rinse the plastic bottles 3 times the
bottles were not filled when rinsing and the bottles were capped each time while
rinsing at both localities (EUS and EDS). When collecting the water sample the
64

plastic bottle was immersed in the stream in an upstream position avoiding
sediment disturbance and inflow of surface films the plastic bottles were filled to
the top and capped then placed in the cooler box with blue ice bottles.
Furthermore, a 50 mL syringe was submerged into the stream and slowly the
plunger was pulled to draw 20 mL of sample water to rinse the syringe 3 times by
holding the syringe up and shaking vigorously and pushing down the plunger to
withdraw the water. A 45 μm membrane filter was attached. The syringe with the
filter was submerged in the stream and the plunger was pulled up as in the above
statement and the sample water was drawn and transferred into the 50 mL
polyethylene bottles 3 times for rinsing the bottles were capped each time rinsing
was done the water samples were collected in the same manner in which 50 mL of
the filtered sample was transferred into polyethylene bottles and acidified with
nitric acid the water sample was filled to the top and sealed then placed in the
cooler box with blue ice bottles.
3.2.3 Stratification
We used a dipper and divers for stratification measurements in the three shafts of
Edendale Lead Mine. These two instruments measure chemical (electrical
conductivity) and thermal (temperature) information at a certain depth (water level)
on-site. A dipper is an instrument used to measure water level. It is made up of a
flat tape which is wired and attached to a probe which senses water and causes a
buzzer to beep (Brassington, 2007).We used a dipper which was 150 m we took
measurements of EC and temperature at depth. The dipper was lowered down the
shaft and it buzzed when the probe contacted water. Measurements were taken
65

every 0.5 – 1.0 cm down the shaft recording temperature and EC.
3.2.4 Mine water tracing
Sodium Chloride was used as a tracer when tracing mine water for the
determination of hydraulic parameters in the mine water of the abandoned
Edendale Lead Mine. The tracer test was conducted from September 2016 to
January 2017. The amount of tracer needed for the tracer test was calculated prior
to the test itself and divers were used to monitoring the mass outflow. Divers are
known as dataloggers used for long-term measurements of water level,
temperature and electrical conductivity. In the laboratory, 21 kg of sodium chloride
was dissolved in 75 L of tap water three days before the tracer test.
The divers were installed at E13 and EPD, the divers were set to read data every
20 minutes for the duration of the tracer using the diver software. The CTD diver
was used to measure EC at a range of 0- 120 mS/cm and a baro diver to
compensate the barometric pressure. The solute was injected into shaft 12, to
make sure that the entire tracer was poured down the shaft the bottles were
constantly stirred up while injecting the tracer.
3.2.5 Analytical methodology
When all water samples were collected both the acidified and non-acidified
samples were taken to Waterlab (Pty) Ltd for analysis. Ion chromatography and
Inductively Coupled Plasma–Mass Spectrometry or Inductively Coupled Plasma–
Optical Emission Spectrometry were used for the analysis of element
66

concentration. ICP was used for main ion analysis and for trace elements ICP-MS
or ICP-OES.
67

4 RESULTS AND DISCUSSION
4.1 INTRODUCTION
This chapter represents the results from laboratory analysis of water samples
collected from the study area also stratification and tracer test are presented. The
data for the study is given in appendices: on-site parameters: Appendix1; major
ions and trace elements: Appendix 2; stratification: Appendix 3; tracer tests:
Appendix 4.
4.2 ON-SITE PARAMETERS
The on-site parameters provide understanding into the mine water chemistry as a
result making them important. On-site parameters results are discussed here
focusing on pH, redox potential, electrical conductivity, temperature, and dissolve
oxygen saturation and percentage. Table 4.5: On-site parameters from the
abandoned Edendale Lead Mine. n: on-site parameter; ± is the standard deviation
of the sample population. Average of the pH calculated using the [H+].shows an
average of on-site parameters.
Table 4.5: On-site parameters from the abandoned Edendale Lead Mine. n: on-site
parameter; ± is the standard deviation of the sample population. Average of the pH
calculated using the [H+].
68

EUS E12 E13 EPD EDS
pH 6.9 ± 0.4 6.7 ± 0.1 6.7 ± 0.2 6.7 ± 0.4 6.6 ± 0.7
Redox,
mV
328 ± 123 319 ± 42 306 ± 86 224 ± 65 227 ± 65
EC,
μS/cm
437 ± 134 603 ± 15 466 ±118 615 ± 18 670 ± 84
Temp, °C 21.5 ± 2.5 22.9 ± 1.3 23.8 ± 2.0 21.8 ± 2.1 22.0 ± 1.5
DO, mg/L 4.5 ± 2.0 2.1 ± 3.4 2.8 ± 2.8 2.0 ± 2.2 3.3 ± 2.3
DO, % 55.9 ± 25.3 10.9 ± 8.8 16.8 ± 13.7 14.2 ± 16.6 34.5 ± 35.2
n 3 9 9 10 3
The pH was measured on-site at each sample point every time the samples were
collected. Figure 4.14shows the plot of pH values against the date of the
measurement. The average of the pH values is calculated using the arithmetic
average for [H+].The pH values range from an average of 6.3 to 6.9 at E01 and
EUS respectively. The mine water in shafts E12, E12 and at EPD the discharge
point have same pH average of 6.7 however, at EDS in the Edendalespruit has
lower pH average of 6.6 compared to the pH at EUS (Error: Reference source not
found). The mine water and the Edendalespruit water have circumneutral pH
between 6 and 8 (Figure 4.14). The South African National Standard (SANS) for
69

domestic water requires the pH to be greater than 5 and below 9.7 but Target
Water Quality Range (TWQR) pH standard is 6 or 9. The measured pHs at sample
sites are within the standard of the domestic water requirement and therefore
there is no problem with regard to pH of the mine water and Edendalespruit. All
five sample sites have average pH values approaching 7 proposing a carbonate
neutralization influence from the host rocks. All samples show that the water of the
abandoned Edendale Lead Mine (ELM) is within the acceptable range for
domestic use according to DWAF (1996). Higher pH results in a bitter taste in
water while lower pHs are known to dissolve metals and other substances causing
corrosion.
Figure 4.14: pH from the abandoned Edendale Lead Mine
Redox potential is measured with the secondary electrode and the results have
70

been re-calculated to the standard hydrogen electrode as a result of adding the
temperature dependent factor on the measured cell potential using equation 16
(Wolkersdorfer, 2008) to the real mV value measurements used to interpret the
on-site information. E0: converted redox potential, mV, ET: measured OPR at
temperature T, mV; T measured temperature, °C; a, b: empirical electrode
dependent coefficients (for the Hanna Ag/AgCl, KCl, 3.5mol/L: a= 49.296, b= 298).
E0 (25° C )=ET −0.198 · ( T −25 ) + √ a−b ·T (16)
The redox potential results are presented in Figure 4.15 shows the corrected ORP
values. Redox potential average ranges from 445 mV at E01. The ORP average at
EUS is high in comparison to E12, E13, EPD and EDS. On average redox
potential at EPD is the lowest at 224 mV while the redox in the shafts is higher at
319 mV and 306 mV in E12 and E13 respectively (table ##). Figure 4.15 shows
E01 with high redox potential values above 300 mV, however, EUS, E12, E13,
EPD and EDS have redox values above 90 mV and below 400 mV.
71

80
130
180
230
280
330
380
430
480
530
Redox, mV
Date
E01
E12
E13
EDS
EPD
EUS
Figure 4.15: Redox (mV) from the abandoned Edendale Lead Mine
Eh values greater than 450 mV, indicating oxidising conditions, due to the
relatively fast ground water circulation through karst features and fractures. Eh
values less than 300 mV, indicating slightly reducing conditions; this might reflect a
slower underground circulation since these samples were located close to the
contact between the meta-sandstones and shales, respectively, and carbonate
rocks (Cidu et al., 2007)
Electrical Conductivity is known as the measure of water ability to allow electrical
flow proportional to the amount dissolved salts and inorganic materials such as
alkalis, chlorides, sulphate and carbonate compounds (Edition, 2008). EC
measures the concentration of dissolved ions in water. Figure 4.16 shows the
highest EC values measured at EDS and the lowest EC measured at EUS (775
μS/cm and 248 μS/cm). The EC in E12 ranges between 580 μS/cm and 622
72

μS/cm with an average of 603 μS/cm this is higher compared to EC in E13 that
ranges from 274 to 601 μS/cm with an average of 466 μS/cm. The electrical
conductivity average ranges from 356 μS/cm to 670 μS/cm at E01 and EDS
(Error: Reference source not found).The EC at EDS, E12 and EPD are similar
values at 603 μS/cm, 615 μS/cm and 670 μS/cm respectively, however, lower EC
is at E01, EUS and E13 shown in Error: Reference source not found. The more
ions that are present, the higher the conductivity of water. Also, the fewer ions that
are in the water, the lower the conductive. It is seen in the water chemistry results
that the concentrations are low and as a result, the EC is within 0-800 μS/cm
range good drinking water for humans (as long as there is no organic
contaminates).
,
Figure 4.16: Electrical Conductivity (μS/cm) from the abandoned Edendale Lead Mine
Temperature results presented in Figure 4.17 shows that temperature varies from
73

18 °C to 28 °C. The ambient temperature in Pretoria is # groundwater and surface
waters are known to mimic the ambient surrounding temperatures. EUS has a low-
temperature average of 21.5 °C in comparison to other sample sites while EPD
has an average temperature of 21.8 °C close to that of EUS however, temperature
average in E13 is the highest at 23.8 °C Error: Reference source not found. High
temperatures influences oxygen availability in water, the higher the temperature
the lower the dissolved oxygen. It will be shown later the effect of temperature in
relation to stratification.
Figure 4.17: Temperature (°C) from the abandoned Edendale Lead Mine
The dissolved oxygen (DO) concentration average range from 4.5 mg/L to 2 mg/L
at EUS and EPD respectively table##. The dissolved oxygen concentrations are
below 15 mg/L. Figure 4.18 shows lowest DO concentrations at E12, E13 and
74

EPD below 1 mg/L. In the Edendalespruit at EUS and EDS show DO below 2
mg/L while E01 has to DO below 3 mg/L. High DO value in E12 at 11.6 mg/L and
in E23 at 9.80 mg/L. The low DO in the Edendalespruit could be because of
bacteria which use up the oxygen or the biological oxygen demand by plants in the
Edendalespruit stream water and also because of the water warmth. The average
DO saturation values range from 0.37 % at E13 to 84.7 % at EUS with an average
of 55.9 % (Figure 4.19) showing water ranging from low oxygen content to a high
oxygen content.
Figure 4.18: Dissolved Oxygen (mg/L) from the abandoned Edendale Lead Mine
75

Figure 4.19: Dissolved Oxygen (%) from the abandoned Edendale Lead Mine
76

4.3 WATER CHEMISTRY
The values from analytical data from samples which were collected at different
locations were compared alongside one another Figure 4.20 represents the
concentration of major ions and trace elements results. The concentrations of
most major ions and trace elements were below detection limit Appendix #. The
piper diagram shows the type of water that is found at Edendale Lead Mine Figure
4.21.
Arsenic in all water samples collected at EUS, E12, E13, EPD, EDS (Figure 4.20)
is above the 0.001 mg/L as stipulated by WHO groundwater standards. The
concentration of arsenic is the lowest at E13 (0.01 mg/L) and highest at EUS, E12
and EDS (0.03 mg/L) even so these concentrations are very low. The Ba
concentrations are low as well within the recommended groundwater standard
WHO 0.7 mg/L. However, very low concentrations are at EUS and there is an
increase of Ba concentrations in E12 and E13 (0.13 mg/L and 0.10 mg/L)
respectively with a decrease in the discharge point (0.08 mg/L) and EDS (0.07
mg/L).
Figure 4.20 shows high Ca concentrations above the 32 mg/L set by WHO, The
highest concentration at EPD, EDS and E12 (63 mg/L, 61 mg/L and 58 mg/L) and
low concentrations at EUS with 39 mg/L and 41 mg/L at E13. The concentrations
of chlorine are the same (5.0 mg/L) at EUS, E12, E13 and EPD and 4 mg/L at
EDS the concentrations are within the 100 mg/L groundwater standard WHO.
77

Iron concentrations are fairly low below 3 mg/L required by WHO. Even so, Fe
concentration at E12 is high compared to other samples. EUS, E13 and EDS show
the same Fe concentration of 0.02 mg/L while EPD has a sight difference with
0.05 mg/L. Ga has no standard limit and very low concentrations are present in
water samples. The highest concentration is at EPD in comparison with other
samples while the lowest concentration is at EPD (Figure 4.20
High concentration of potassium causes nausea and vomiting even neurological
damage however the potassium concentrations at all sample sites are within 50
mg/L recommended by WHO groundwater and surface water standards. There is
the high concentration at EPD (4.4 mg/L) and low potassium concentration at EDS
(1.5 mg/L) Figure 4.20. There are similar concentrations at EUS, E12 and E13
(3.5mg/L, 3.7 mg/L, and 3.0 mg/L) respectively.
There are high concentrations of magnesium above the required WHO standard of
30 mg/L at EDS, EPD, E12 and EUS (51 mg/L, 39 mg/L, 37 mg/L and 31 mg/L)
and lower concentration at E13 (25 mg/L) that is within the WHO standard.
Manganese concentrations are above WHO groundwater and surface water
standard 0-0.05 mg/L in all samples (Figure 4.20). At EUS concentration is 0.12
mg/L and 1.74 mg/L at E13 there are no health effects associated with these
concentration values but a change in water colour also increased after taste can
be experienced with concentrations above 2 mg/L.
Sodium concentrations are high Figure 4.20 but within the WHO groundwater
standard of 100 mg/L. The highest concentration is at EDS with the lowest at E13.
78

There is only a slight difference in the sodium concentrations at E12 and EPD (9.3
mg/L and 9.6 mg/L). Nickel was extremely low and below detection limit at EPD.
The lead was only detected at E13 with a concentration of 0.024 mg/L that is
above WHO standard of 0.001 mg/L.
Sulphate was higher at EDS (102 mg/L) relative to EUS (55 mg/L) Figure 4.20 but
not above the 200 mg/L recommended by WHO. Very low sulphate concentrations
are at E12, EPD and E13 (0.6 mg/L, 5 mg/L and 27 mg/L) respectively. There is
no WHO standard set for silicon the concentrations. Nevertheless, concentrations
are high at E12 (19 mg/L), EDS (17 mg/L), EPD (16 mg/L), E13 (13 mg/L) and
EUS (12 mg/L). Strontium and zinc concentrations are very low below 1 mg/L and
Rb is only detected at EUS.
Major ions in water samples are an important part of the classification of water
type. Other ions were detected at low concentrations NO3 (<0.1 -0.1 mg/L), NO2
(<0.5- 5 mg/L), F- (<0.2 – 0.2 mg/L), PO43- (0.1 mg/L), NH4 (0.1 – 0.2 mg/L). In a
Piper diagram, it can be seen that the mine water of the Edendale Lead Mine is
alkaline Figure 4.21. Mine water characterized at EPD is in the HCO3 type while
E12, E13, EUS and EDS are dominated by the Mg-Ca type, so as in E13 and
EUS, the SO4 type is introduced and Cl type is also introduced at E13. The
samples show relatively more alkaline earth metals then alkali metals. The main
rock type found in the study area is limestone and dolomite, which explains the
concentrations of Mg, Ca and bicarbonate in most of the samples.
79

0,00
0,01
0,10
1,00
10,00
100,00
1000,00
As Ba Ca Cl Fe Ga K Mg Mn Na Ni Pb SO4 Si Sr Rb Zn
Concentration, mg/L
Elements
EUS E12 E13 EPD EDS
Figure 4.20: Element concentration
Figure 4.21: Piper diagram for samples collected at the abandoned Edendale Lead Mine;
n = 15, averages of three sampling campaigns.
80

4.4 STATISTICAL ANALYSIS
The data were statistically analysed using the Past3 computer software. ANOVA
was used to compare the average trace metal and main ion (elements)
concentrations of all samples. The interpretation was performed at α = 0.05 (two-
sided) where
Ha: diff < 0 Ha: diff != 0 Ha: diff > 0
Pr(T < t) = 0.0028 Pr(|T| > |t|) = 0.0057 Pr(T > t) = 0.9972
81

4.5 STRATIFICATION
All the three shafts that stratification data was collected were investigated
individually and inputted into excel. Stratification takes place when there is a
change in density. This change in density is represented by a depth-dependent
graph with a vertical change of temperature and electrical conductivity parameters.
The temperature and conductivity profiles are represented in (Figure 4.22 to
Figure 4.28) monitored from January 2016 to September 2016 before the tracer
test was conducted.
Figure 4.22 represents temperature and electrical conductivity profiles measured
from E01, E12 and E13 January 2016. The temperature and conductivity profile at
shaft E01 shows shallow waters with high EC and temperature and deep waters
with lower EC and lower temperature E12 shows comparable temperature and
EC. E13 has low EC and high temperature at shallow waters and higher EC and
low temperature in deep waters.
The temperature and electrical conductivity profiles measured from E01, E12 and
E13 in March 2016 (Figure 4.23) E01 has higher temperatures (23 – 25 °C) and
higher electrical conductivity in the higher parts of the shaft and lower temperature
(22 – 20 °C) and lower electrical conductivity in the deeper parts of the shaft.
Likewise, E12 shows higher temperature and electrical conductivity in the upper
parts of the shaft and lower temperatures and electrical conductivity in the lower
parts of the shaft. In contrast, E13 shows lower electrical conductivity in the upper
parts and higher ones in the deeper parts of the shaft the temperature is again
82

high in the upper parts and low in the deeper parts of the shaft.
Stratification measurement conducted in April 2016 in E01, E12 and E13 (Figure
4.24). The temperature and electrical conductivity profile of E01 show constant
higher temperature and electrical conductivity in shallow waters with lower
temperatures and electrical conductivity in deeper waters. The temperature and
electrical conductivity profile in E12 again show higher temperature and electrical
conductivity in shallow waters and lower ones in deeper waters. However, E13 has
a lower temperature and electrical conductivity in shallow waters and higher
temperature and electrical conductivity in deeper waters.
83

Figure 4.22: Stratification on shaft E01, E12 and E13 in the abandoned Edendale Lead
Mine January 2016
Figure 4.25 represent temperature and electrical conductivity profile measured in
June 2016. E01 temperature and electrical conductivity show high temperature in
shallow waters and constant in deeper water with no variation and higher electrical
conductivity in deeper waters with low electrical conductivity in shallow waters.
The stratification in E12 shows higher temperature and electrical conductivity in
84

shallow waters and lower temperature and electrical conductivity in deeper waters.
In E13 temperatures are lower in shallow waters and higher in deep waters while
there was constant electrical conductivity (431μS/cm) in shallow and deeper
waters.
Figure 4.23: Stratification on shaft E01, E12 and E13 in the abandoned Edendale Lead
Mine in March 2016
In July 2016 temperature and electrical conductivity profile Figure 4.26 show a
decrease in water level at E01 with higher temperature and electrical conductivity
85

in upper waters and lower temperature and electrical conductivity in deeper
waters. However, E12 shows constant temperature (21.2 °C) in shallow waters
and (21.1 °C) in deeper waters with higher electrical conductivity in shallow waters
and lower ones in deeper waters. The profile in E13 again shows higher
temperatures and electrical conductivity in shallow waters and lower temperature
and electrical conductivity in deeper waters.
Figure 4.24: Stratification on shaft E01, E12 and E13 in the abandoned Edendale Lead
Mine in April 2016
86

The water in E01 was out of reach in August 2016 represented in Figure 4.27. The
temperature and electrical conductivity profile of E12 show again a well-stratified
water body with higher temperatures and electrical conductivity in shallow waters
and lower temperatures and electrical conductivity in deeper water. But the
stratification in E13 has higher temperatures in shallow waters and lower ones in
deeper waters with a constant electrical conductivity of 540 μS/cm at all water
depth.
87

Figure 4.25: Stratification on shaft E01, E12 and E13 in the abandoned Edendale Lead
Mine in June 2016
In September 2016 before the tracer test was conducted, the water in E10 was
again out of reach Figure 4.28. E12 has higher temperatures and electrical
conductivity in shallow waters and lower temperatures and electrical conductivity
in deeper waters. Even so, E13 has constant temperatures at 22.5 °C at all depth
and constant electrical conductivity of 290 μS/cm at all depth this is very low in
comparison to other values in the same shaft in previous months.
88

Figure 4.26: Stratification on shaft E01, E12 and E13 in the abandoned Edendale Lead
Mine in July 2016
89

Figure 4.27 Stratification on shaft E12 and E13 in the abandoned Edendale Lead Mine in
August 2016
Figure 4.28: Stratification on shaft E12 and E13 in the abandoned Edendale Lead Mine
September 2016
90

4.6 TRACER TEST
The use of artificial salts in karstic environments dates back before the 1960s. Salt
tracers are effective as they are less sensitive in comparison to artificial dyes. The
dissolution of salts into cations and anions increases ion mobility that causes
elevated electrical conductivity (Leibundgut et al., 2011). Sodium chloride was
used as a tracer in the determination of hydraulic connectivity of the shaft E12 and
E13 at Edendale Lead Mine because it is nontoxic, cheap, abundantly available
and has less potential of sorption, however, the natural occurrence of NaCl may
cause high background concentrations (Leibundgut et al., 2011). Tracer detection
is done through continuous measurement of chloride ion (EC). The tracer test was
conducted from September 2015 to January 2016.
The continuous measurement of electrical conductivity at E13 and EPD was used
as a tracer mass detector Figure 4.29 shows that electrical conductivity at E13
range from 0.4 mS/cm to 0.6 mS/cm and EPD has an electrical conductivity of 0.2
mS/cm to 2.6 mS/cm. During the tracer test, the electrical conductivity increased in
the wet months (Figure 4.29) which can clearly be attributed to the sodium chloride
tracer (Wolkersdorfer et al. 2002) being transported by the rain water infiltrating
into the subsurface. Only 17.1% of the injected tracer was recovered Figure
4.30Figure 4.29. Considering the geological and hydrodynamic setting, the low
recovery rate might be caused by a poor hydraulic connectivity between the point
of injection and point of discharge or a density-driven settlement of the
concentrated tracer. The first EC peak occurred in October 2015, second, third
and fourth peaks were detected in November, December and January
91

respectively. When there are multiple peaks in the EC measurement it shows that
the tracer might be transported via various flow paths so as the dispersion and
velocity are not the same (Leibundgut et al. 2011) or rain events cause the tracer
to be flushed out of the mine. No peaks were observed in E13 (Figure 4.29).
Therefore, it can be assumed that the tracer does not flow into shaft E13. This
result shows that the tracer is transported from shaft E12 directly to the point of
discharge but not to the adjacent shaft E13.
Recovery rate refers to
0,0
0,5
1,0
1,5
2,0
2,5
3,0
2015-09-17 2015-10-07 2015-10-27 2015-11-16 2015-12-06 2015-12-26 2016-01-15 2016-02-04
EC, mS/cm
Date
EPD E13
Figure 4.29: EC measurement in shaft E13 and discharge point of the abandoned
Edendale Lead Mine during tracer test
92

0%
1%
2%
3%
4%
5%
6%
7%
8%
9%
10%
11%
12%
13%
14%
15%
16%
17%
18%
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
Recovery rate, %
Time after injection , days
Figure 4.30: Recovery rate of the Edendale tracer test.
93

5 CONCLUSION AND RECOMMENDATIONS
If this trend continues, groundwater in flooded mines could be regarded as an
important water resource, especially for industrial uses. The hydrogeochemical
approach appeared to be a valuable tool for the understanding of processes
occurring during rebound; monitoring of the water quality in the flooded mines
should continue to pinpoint eventual variations related to extraction. Detailed
knowledge of the composition of the host rocks, ore minerals, and mine wastes
would be necessary in order to better understand the water-rock interaction
processes and the geochemical behaviour of each metal
94

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114

APPENDIX I
115

Water Samples co-ordinates
116