ABSTRACT
The distribution of metal contaminants in Azare groundwater system was
investigated in this study. Concentrations of total and soluble forms of K,
Ca, Mg, Cu, Zn, Mn, Pb and Cd were determined in randomly selected
twenty boreholes and twenty hand-dug wells within Azare town using flame
Atomic Absorption Spectroscopy. Findings revealed that, the mean total
concentrations of K, Ca, Mg, Cu, Zn, Mn, Pb and Cd in borehole waters
were 0.3233±0.2455mg/L, 0.5433±0.1762mg/L, 0.3178±0.1641mg/L,
0.2386± 0.1361mg/L, 0.3260 ± 0.3187mg/L, 0.1879± 0.1082mg/L, 0.1234 ±
0.1480mg/L, and 0.0049 ± 0.0037mg/L respectively while the mean total
concentrations of K, Ca, Mg, Cu, Zn, Mn, Pb and Cd in well waters were
0.8790± 90.6823mg/L, 1.1923±1.1337mg/L, 0.9543±1.0186mg/L, 0.0953±
0.1083mg/L, 0.1890±0.0791mg/L, 0.1645±0.1238mg/L, 0.0965±
0.0491mg/L, and 0.0041±0.0034mg/L respectively. It was also discovered
that in all the samples investigated, concentrations of Cu and Zn were found
below the Maximum Contaminant Levels (MCLs) for these metals in
drinking water (MCL for Cu = 1.3mg/L and MCL for Zn = 5.0mg/L) while
the total concentration of Pb exceeded the MCL for this metal in drinking
water (MCL for Pb = 0.015mg/L). Concentrations of total Mn exceeded the
MCL for this metal (0.05mg/L) in all the borehole waters investigated but it
only exceeded the MCL for this metal in 95% of the well waters
investigated. The concentrations of total Cd was found to exceed the MCL
for this metal (0.005mg/L) in 45% of the borehole waters and 35% of the
well waters investigated in this study. Apart from K and Cu, no significant
differences were found between the mean concentrations of total metal
contaminants in boreholes and hand-dug wells investigated. Findings also
revealed that on the average, K, Ca, Mg, Zn and Mn exist predominantly in
the soluble phase while Cu, Pb and Cd exist predominantly in the particulate
phase. The average proportions of the soluble forms of these metals in
boreholes were 84.9% for K, 80.5% for Ca, 88.6% for Mg, 22.2% for Cu,
67.2% for Zn, 56.8% for Mn, 39.9% for Pb and 17.5% for Cd while the
average proportions of the soluble forms of these metals in hand-dug wells
were 93.1% for K, 87.6% for Ca, 91.8% for Mg, 25.5% for Cu, 69.3% for
Zn, 76.5% for Mn, 44.5% for Pb and 42.5% for Cd. Implications of the
findings were discussed and some useful suggestions given.
TABLE OF CONTENTS
Cover Page i
Fly Leaf ii
Title Page iii
Declaration iv
Certification v
Acknowledgements vi
Abstract vii
Table of Content viii
List of Tables xi
List of Figures xii
List of Appendices xiii
Abbreviations, Definitions and Symbols xv
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study 1
1.2 Purpose of the Study 4
1.3 Research Hypothesis 4
1.4 Significance of the Study 5
1.5 Scope and Limitation of the Study 5
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 Hydrological Cycle and Self-Purification Mechanism of Water 7
2.2 Sources and Effects of Metal Contaminants in Groundwater 9
2.2.1 Sources and Effects of Potassium 11
2.2.2 Sources and Effects of Calcium 13
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2.2.3 Sources and Effects of Magnesium 14
2.2.4 Sources and Effects of Copper 16
2.2.5 Sources and Effects of Zinc 18
2.2.6 Sources and Effects of Manganese 20
2.2.7 Sources and Effects of Lead 21
2.2.8 Sources and Effects of Cadmium 25
2.3 Metal Contaminants and their Maximum Contaminant Levels in
Drinking Water 26
2.4 Fate and Transport of Metal Contaminants in Natural Water 28
2.5 Metal Speciation in Natural Water 31
2.6 Principle and Applications of Atomic Absorption Spectrometry 34
CHAPTER THREE
3.0 EXPERIMENTALS
3.1 Description of the Study Area 36
3.2 Materials and Reagents 37
3.2.1 Materials Required 37
3.2.2 Reagents Required 37
3.3 Collection and Preservation of Samples 40
3.3.1 Collection of Samples 40
3.3.2 Preservation of Samples 40
3.4 Preparation of Samples 41
3.4.1 Filtration Procedure 41
3.4.2 Digestion Procedure 41
3.4.3 Preparation of Samples for Potassium, Calcium and Magnesium
Determination 42
3.4.4 Preparation of Samples for Heavy Metals Determination 43
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3.5 Preparation of Standard Solutions and Reagent Blanks 43
3.5.1 Preparation of Standard Solutions for Potassium, Calcium and
Magnesium 43
3.5.2 Preparation of Standard Solutions for the Heavy Metals 44
3.5.3 Preparation of Reagent Blanks 45
3.6 Analytical Techniques 45
3.6.1 Preparation of Calibration Curves 45
3.6.2 Determination of Metal Concentrations in the Samples 46
3.7 Method of Data Analysis 46
CHAPTER FOUR
4.0 RESULTS AND DISCUSSION
4.1 Results of Total Concentrations of Metal Contaminants in Azare
Groundwater 47
4.2 Comparison of Total Heavy Metal Concentrations with their Maximum
Contaminants Levels in Drinking Water 53
4.3 Comparison of Mean Concentrations of Metal Contaminants in
Boreholes and Hand-Dug Wells 67
4.4 Distribution of Metal Contaminants between the Soluble and Particulate
Phases in Groundwater 78
CHAPTER FIVE
5.0 SUMMARY, CONCLUSION AND RECOMMENDATION
5.1 Summary and Conclusion 82
5.2 Recommendations/Suggestions for Further Study 84
REFERENCES 86
APPENDICES 95
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CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study
Azare is the headquarter of Katagum local government area in Bauchi
state of Nigeria. It has a population of over one hundred and fifty thousands
according to the 1991 population census (Shehu, 2000). Azare is often
regarded as the second most developed city in the state, in terms of provision
of social amenities. However, majority of the people in Azare, according to
Alabi (2005), still depend on groundwater (bore-holes and wells) for
drinking and other domestic purposes. It is an age-long belief among the
people that groundwater is pure and safe for drinking but recent discoveries
have shown that like surface water, groundwater is also vulnerable to
contamination from a variety of sources (Texas Environmental Profiles,
2003). According to Ademoroti (1996), groundwater contamination may be
from seepages from agricultural activities, septic systems, and mining
activities and even from geological origin.
Assessing the dangers from metallic contaminants to human healths
involves concerns that are different from those associated with organic
chemicals. Organic chemicals are generally broken down over time in the
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environment but metals are not and can easily be accumulated and
concentrated in living systems (Chemical and Engineering News, 2002).
The considerable interest in, and apprehension about the role and fate
of metals in aquatic systems, as displayed by scientists and regulatory
bodies, is warranted on the grounds of several disasters which are related to
mercury and cadmium poisoning (Forstner and Wittmann, 1979). Although,
metals such as sodium, potassium, magnesium, calcium, manganese, iron,
cobalt, copper and zinc have been shown to be essential to human life
(Shriver and Atkins, 1999) but studies pertaining to the toxicity of these
trace metals, according to Forstner and Wittmann (1979), follow the general
trend that an undersupply leads to deficiency symptoms, sufficient supply
results in optimum conditions, and an oversupply results in toxic effects and
lethality in the end.
Until recently, most environmental research on trace metals were
based on the assessment of the total metal concentration but it is becoming
increasingly evident that the impact of a particular metal species may be
more important than the total metal concentration (Johansson, 1996). It has
also been observed by Goulden (1978) that the toxic effect of metals such as
lead, cadmium and mercury depends largely on whether the metals exist in a
form that is physically available to the living organism rather than the total
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concentration of the toxic metals. Forstner and Wittmann (1979) reported
that when large quantities of silver in the form of soluble silver ions are
ingested, they remain impregnated in tissues forming a stable bond to SH
or SR groupings and this has been shown to be responsible for the
permanent discolouration of skin and eye tissue, a condition known as
argyria. However, most insoluble salts do not pose any health risk to human
if ingested because they are merely excreted in faeces.
A study carried out by Saje (2005) on the determination of heavy
metal constituents of groundwater samples in Azare is considered to be the
only work on Azare groundwater system. The work is inadequate on two
grounds. First, the study is limited in scope both in terms of the number of
samples analyzed and the number of heavy metals determined (only three
metals – Cu, Pb and Zn – were determined in three bore-holes and three
wells). Second, the study was also restricted to the determination of total
heavy metal concentrations in the groundwater samples. On the basis of
these limitations, findings from the study lack the validity for generalization.
The present study focuses on the determination of metal contaminants in
Azare groundwater system on a broader scope with a view to understanding
the distribution patterns of the metals in groundwater system.
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1.2 Purpose of the Study
The general purpose of this study is to investigate the pattern of
distribution of metal contaminants in Azare groundwater system.
Specifically, the study aims at achieving the following objectives:
(i) To compare the total concentrations of the metal contaminants in
Azare groundwater system with the maximum contaminant level
for drinking water standards.
(ii) To compare the total concentrations of the metal contaminants in
bore-holes with those in wells.
(iii) To determine the distribution of each metal contaminant between
the dissolved phase and the suspended sediment in groundwater.
1.3 Research Hypothesis
In order to achieve the second objective stated under section 1.2
above, the following null hypothesis was formulated and tested at 0.01 level
of significance.
Ho: There is no significant difference between the mean total
concentrations of metals in bore-holes and their respective mean
total concentrations in hand-dug wells.
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1.4 Significance of the Study
It is expected that the findings from this study will be of great
importance to researchers in the field of environmental chemistry and the
community in which the samples for the study were collected. Investigators
in environmental chemistry will benefit in three ways. First, the study will
provide a base line data so that, the impact of man’s activities on the quality
of groundwater in Azare, as far as trace metals are concerned, can be
assessed in the future. Second, the study will enable researchers to know if
bore-holes are more vulnerable to contamination by metals than hand-dug
wells or vice-versa. Third, findings from this study will provide an insight
into the natural distribution of metals between the dissolved and the
particulate phases in groundwater.
The People of Azare will also benefit from this study because the
findings thereof will enable them to know the extent at which the ground
waters in Azare have been contaminated by metals.
1.5 Scope and Limitation of the Study
This study is a preliminary investigation geared towards
understanding the distribution of metal contaminants in Azare groundwater
system. Detailed determination of the various forms in which each metal
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contaminant exists in both the dissolved and the particulate phases will not
be investigated. This limitation is imposed on this study because of the lack
of necessary facilities needed to accomplish this aspect of the research.
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