This research work investigated the water and soil pollution status of Asha and Saboeregi mining areas of Niger State using standard analytical methods. The physico-chemical parameters of water (pH, turbidity, total dissolved solids, electrical conductivity, dis-solved oxygen, chloride, alkalinity, sulphide, colour, suspended solid, total solid, bio-chemical oxygen demand, chemical oxygen demand, nitrate and phosphate) as well as soil (pH, organic carbon, organic matter, available phosphorus, cation exchange capacity, sand, silt and clay) were determined. The water, soils and Sorghum bicolor grains were analysed using atomic absorption spectrophotometer to determine the concentrations of Au, Cd, Cu, Fe, Mn, Pb and Zn. Statistical analysis on the results were carried out using One –way analysis of variance (ANOVA). The results indicated that of the fifteen physical and chemical properties of waters from Rivers Gbako and Tangale studied, seven of the properties (turbidity, alkalinity, sulphide,, colour, suspended solid, nitrate and phosphate) exceeded the acceptable World Health Organisation (WHO) standard limits for surface waters while four of these properties (total dissolved solid, electrical conductivity, chloride and biochemical oxygen demand) were found to be below the acceptable WHO standard limits for surface waters and the remaining three properties (pH, dissolved oxygen and chemical oxygen demand) were within the acceptable WHO standard limits for surface waters during the period of study. The distribution of heavy metals in surface water of Rivers Gbako and Tangale indicates that anthropogenic activity was an important factor contributing to increased metals (Au, Cd, Cu, Fe, Mn, Pb and Zn) concentration in the water. The metal concentrations were higher than the values obtained for control sites except for Cd and Pb. The metal concentrations were also higher than the recommended limits given by Joint Food Organization and World Health Organization (FAO/WHO). The soils at Asha mining site were sandy loam while those of Saboeregi were sandy clay loam in texture and showed Saboeregi soils had better structural stability, water holding capacity and high nutrient. The concentrations of the metals (Au, Cd, Cu, Fe, Mn, Pb and Zn) in the soils from the mining sites were higher than the corresponding values from the control sites, and also higher than the recommended limits given by Joint FoodOrganization and World Health Organization (FAO/WHO). The index of geo- accumulation (Igeo) showed that soils at the two study sites (Asha and Saboeregi) were extremely polluted with Fe with Igeo value of 7.43. Heavily to extremely polluted with Mn with Igeo value of 4.41 and heavily polluted with Zn with Igeo value of 3.66. The concentrations of the metals (Au, Cd, Cu, Fe, Mn, Pb and Zn) in the Sorghum grains harvested from the mining sites were higher than the corresponding values from the control site with the exception of Cd and Pb, and also higher than the recommended limits given by Joint Food Organization and World Health Organization (FAO/WHO) with the exception of Cu and Mn.
TABLE OF CONTENTS
Cover page 0 Title page i Declaration ii Certification iii Dedication iv Acknowledgement v Table of Contents vi List of Figures xi List of Tables xii List of Appendices xiv List of Abbreviations xv Abstract xvi
1.0 INTRODUCTION 1
1.1 The Research Problem 2
1.2 Justification of the Study 2
1.3 Aim and Objectives 3
2.0 LITERATURE REVIEW 4
2.1 Effect of Mining on Aquatic Life 6
2.2 The Effect of Mining Processes on the Ecosystem 8 2.3 Effect of Mining Processes on Physicochemical Parameters 9 2.3.1 pH 9 2.3.2 Turbidity 10 2.3.3 Total dissolved solids 10 2.3.4 Electrical conductivity 12 2.3.5 Dissolved oxygen 13 2.3.6 Chloride 14 2.3.7 Total alkalinity 14 2.3.8 Sulphide 14 2.3.9 Colour 14 2.3.10 Suspended solid 15
2.3.11 Total solids 15
2.3.12 Biological oxygen demand 16 2.3.13 Chemical oxygen demand 17 2.3.14 Nitrate 17 2.3.15 Phosphate 18 2.4 Effect of Heavy Metals from Acid Mine Drainage 19 2.5 Fate of Heavy Metal in Soils 20 2.6 Mobility of Heavy Metals in Soils 21
2.7 Plant Uptake of Heavy Metals in Soil 21
2.8 Sources of Contamination and Distribution of some Heavy Metals 22
2.8.1 Gold 22 2.8.2 Cadmium 27 2.8.3 Copper 29 2.8.4 Iron 30 2.8.5 Manganese 33 2.8.6 Lead 34 2.8.7 Zinc 37 2.9 Chemical Speciation 39 2.9.1 The importance of chemical speciation 39 2.9.2 Tessier‘s sequential extraction scheme 40 2.10 Types of Mining Techniques 43 2.11 Soil Type in Niger State 44 2.12 Mineral Resources in Niger State 45
3.0 MATERIALS AND METHODS 46
3.1 The Areas of Study 46 3.2 Sampling Site 46 3.2.1 Sample collection and treatment 46 3.2.2 Chemicals and reagents 51 3.2.3 Determination of soil pH 51 3.2.4 Determination of particle size distribution 51 3.2.5 Determination of organic matter in soil sample 52 3.2.6 Determination of cation exchange capacity 53 3.2.7 Determination of phosphate concentration in soil 55
3.3 Determination of Physicochemical Properties of Water 57
3.3.1 Determination of pH 57 3.3.2 Determination of total solid dried 57 3.3.3 Determination of total dissolved solids 58 3.3.4 Total suspended solid 58 3.3.5 Determination of electrical conductivity 58
3.3.6 Determination of chloride 58
3.3.7 Determination of sulphide 60 3.3.8 Determination of alkalinity 61 3.3.9 Determination of biochemical oxygen demand 62 3.3.10 Determination of chemical oxygen demand 63 3.3.11 Determination of colour 65 3.3.12 Determination of turbidity 66 3.3.13 Determination of phosphate 66 3.3.14 Determination of nitrate 67 3.3.15 Determination of dissolved oxygen 67 3.4 Determination of Au, Cd, Cu, Fe, Mn, Pb and Zn by Atomic Absorption Spectrophotometry 68 3.5 Modified Tessier’s Sequential Extraction 68 3.6 Preparation of Calibration Curves 70 3.7 Quality Assurance for Metal Analysis 71 3.7.1 Preparation of 0.5 mg/dm3 multi-element standard solution 71 3.7.2 Spiking experiment 71 3.8 Statistical Analysis 74 3.9 Indices and Methods for the Assessment of Soil Contamination 74 Chapter Four
4.0 RESULTS 78
4.1 Physico-chemical Parameters and Concentration of Heavy Metals in Rivers Gbako and Tangale Waters 78
4.1.1 Physico-chemical parameters of water 78 4.1.2 Heavy metals in surface water of Rivers Gbako and Tangale 89 4.2 Soil Physico-chemical Characteristics of the Mining Sites 94 4.2.1 Soil textural class of the mining sites 97
4.2.2 Heavy metals in soils of the mining sites 97
4.3 Correlation Analysis 105 4.3.1 Pearson‘s correlation coefficients between the physico-chemical parameters and heavy metals in the waters from the study sites 105 4.3.2 Pearson‘s correlation coefficients between soil physico-chemical characteristics and metals in soils at Asha and Saboeregi mining sites rainy and dry seasons 116 4.3.3 Pearson‘s correlation coefficients between soil metal concentrations and metal concentrations in the Sorghum bicolor grains at the mining sites 121 4.3.4 Pearson‘s correlation coefficients between soil, river water and Sorghum bicolor grains metal concentrations at the mining sites 124 4.4 Heavy Metal Speciation in Asha and Saboeregi Mining Sites 131 4.5 Pollution Indices in the Study Sites 140 4.5.1 Pollution degree based on Igeo 140 4.5.2 Pollution degree based on enrichment factor 140
5.0 DISCUSSION OF RESULTS 143
5.1 Physico-chemical Parameters and Concentration of Heavy Metals in Rivers Gbako and Tangale Waters 143 5.1.1 Physico-chemical parameters of water 143 5. 1.2 Heavy metals in surface water of Rivers Gbako and Tangale 152 5.2 Soil Physico-Chemical Characteristics of Asha and Saboeregi Mining Sites 158 5.2.1 Soil textural class of the mining site 161 5.2.2 Heavy metals concentrations in soils of Asha and Saboeregi mining Sites 161 5.3 Mean Heavy Metals Concentration in theSorghum bicolorgrains Cultivated in the Mining Vicinity 166 5.4 Pearson’s Correlation Coefficients Analysis Between Physico-Chemical Parameters, Soil, River Water and Sorghum bicolor Grains Metal Concentrations at the Mining Sites 170 5.5 Heavy Metal Speciation in Asha and Saboeregi Mining Sites 172 5.6 Pollution Degree Indices in the Study Sites 177 5.6.1 Pollution degree based on Igeo 177 5.6.2 Pollution degree based on enrichment factor 178
Chapter Six 6.0 SUMMARY, CONCLUSION AND RECOMMENDATIONS 179 6.1 Summary 179 6.2 Conclusion 180 6.3 Recommendations 181
Pollution may be defined as the contamination of earth’s environment with materials that interfere with human health, quality of life or natural functioning of ecosystem. Such contaminants may be gases causing air pollution, solids/liquids causing water, food and land pollution or sound causing sound pollution. Most of these pollutions except few (such as volcanic eruptions) are caused by human activities. Pollution has been aggravated by marked increase in global population, poverty, increased industrialisation, and urbanisation in developed countries since the beginning of the 20th century.Thus environmental pollution is largely associated with the past and present industrial activities which immensely contributed to the release of significant level of metals to the environment (Dolam et al., 2006). The use of metals in human history has yielded great benefits as well as unexpected harmful consequences. Metals as a group share some common properties. However, while sharing common properties, metals exhibit wide ranges with respect to one another, in both chemical behaviour and measured values of those common properties. Historically, it has been the exploitation of these properties of metals and the dependence of the modern technological development that led to the increasing demand for these metals. It is their chemical and radioactive behaviour in biological systems (toxicity, mutagenicity, and carcinogenicity), realized within the past century, which pose the most serious risks. The elements of greatest concern include Pb, Cd and Hg, and As. Other different types of metals, like Be, Sr, and Ba (alkaline earth metals), and U and Th (rare earth metals) also pose problems (Lake et al., 1984; Pickering, 1986).
1.1 The Research Problem
The Mining operations take a heavy toll on the environment and its associated biota through the removal of vegetation, topsoil and the displacement of fauna.The release of heavy metals from the mining waste is particularly problematic as they do not chemically break down in the environment. They settle or persist in streams or land for long period of time, providing a long-term source of pollution to the surrounding inhabitant‘s especially human health. In most cases the extent of this threat is not known as the heavy metal level is sometimes not established. Frequent exposure to mine waste may lead to chronic or acute disease. Other environmental problems in mining include the release of metallic smoke and dust into the atmosphere, dumping of waste rock, tailings or slag, and the discharge of mine pit water or waste water.
1.2 Justification of the Study
Mining of mineral resources has assumed prime importance globally, contributing immensely to the national wealth with associated socio-economic benefits.World Health Organization (WHO , 2011) estimates that about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution (Prüss-Üstün and Corvalán, 2006; Kimani, 2007).
With rapid increase in mining process of extracting metals and minerals from the earth, the effects on the environment (if protective measures are not taken) can be unnaturally high in concentrations of some chemicals, such as arsenic, sulphuric acid, and mercury (Nordstrom et al., 2000). Runoff of soil or rock debris -although non-toxic- also devastates the surrounding vegetation. There is an additional potential for massive contamination of the area surrounding mines due to the metals removed from the ground with the ore. Large amount of water produced from mine drainage, mine
cooling, aqueous extraction and other mining processes increases the potential of these chemicals to contaminate ground and surface water (Adler et al., 2007). It is therefore of utmost importance to monitor the mining environment constantly, to prevent disasters arising from the introduction of heavy metals into the soil, water and plants. Monitoring the levels of heavy metals in the soil will also provide an indication to policy-makers of the pressing need to enforce compliance by various companies and industries.
1.3 Aim and Objectives
The aim of this study is to determine the level of pollution caused by mining activities on soil, water and plants in Asha and Saboeregi areas of Niger State. This aim will be achieved through the following objectives:
i. Determination of physico-chemical properties and the concentration of heavy metals (Au, Cd, Cu, Fe, Mn, Pb, and Zn) in soil and
ii. Determination of physico-chemical properties and the concentration of heavy metals (Au, Cd, Cu, Fe, Mn, Pb, and Zn) in water within the study area
iii. Determination of these metals in the Sorghum bicolor grains cultivated within the area
iv. Establishment of relationship between soil properties and the heavy metals in the soils, water and grains.
v. Determination of pollution index in order to ascertain the pollution status of the soil at the mining sites.
vi. Speciation of Au, Cd, Cu, Fe, Mn, Pb, and Zn metals in the soil using sequential extraction procedure in order to establish the bioavailability of the metals.
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