ABSTRACT
Soil characterization and levels of heavy metals in two different soil depths (0 – 15 cm and 15 – 30 cm depth) and well water ofautomobile mechanic workshop soil at Zawangi, Crowther Memorial, Lokongoma Phase 1, Lokongoma Phase 2, Felele , and first 200 unit areas of Lokoja metropolis, Nigeria werecarried out between September and December, 2014.The physicochemical parameters of the soil such as pH, particle size, cation exchange capacity (CEC), organic matter (OM), electrical conductivity, phosphates and sulphates were determined. The soil samples were subjected to sequential extraction to ascertain the mobility of the metals in the soils. Statistical analysis on the data obtained was carried out using One- way ANOVA. The results indicated that the soils at the experimental and control sites were a mixture of sandy loam, clay and slightly acidic. The %OM and CEC for the experimental soils were higher than the soils of the Nigerian Savanna.The concentrations of the studied metals (Zn-64.00mg/kg, Pb-45.22mg/kg, Cd-2.84mg/kg, Fe-151.58mg/kg and Ni-16.06mg/kg) in the soils from experimental sites were higher than the corresponding values from the control site (Zn-5.75mg/kg, Pb-2.07mg/kg, Cd-1.90mg/kg, Fe-36.65mg/kg and Ni-2.1mg/kg), and also, higher than the recommended limits given by the World Health Organization (WHO). The soil samples showed remarkably high levels of all the metals (Ni, Fe, Zn and Pb) above background concentrations with most of them decreasing with decrease in soil depth. The distribution was in the following order Fe> Zn> Pb > Ni > Cd. Across the sampling locations and profiles, Fe and Cd gave the highest (154.58 mg/kg) and least (2.54 mg/kg) values respectively. Pollution load index (PLI) andgeoaccumulation index(Igeo) revealed overall high and moderate contamination respectively while theenrichment factors (EFs) for Zn
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and Ni were severe. The inter-elemental relationship revealed anidentical source of elements in the soils of the studied areas. The levels of metal in well water within the mechanic workshops at different distances of 20m and 30m away from each location were determined.The results indicated that, the levels of metal in well water were higher in 20m than 30m away from the mechanic workshops. At 20m, Zn was the highest in Lokongoma phase1 (14.03 mg/kg) and least at Zanwangi (1.16 mg/kg ), Pb was highest in Lokongoma phase1(1.96mg/kg ) and least in Crowther Memorial and Felele (1.56 mg/kg ), Cd was the highest in Lokongoma Phase1(0.21 mg/kg ) and least in Lokongoma Phase2(0.15mg/kg ), Fe was the highest in Lokongoma Phase1 (1.73mg/kg ) and least in Crowther Memorial and Felele (0.83mg/kg ) and Ni was the highest in 200Unit (45.55 mg/kg) and least in Felele (0.07 mg/kg ). While at 30m, Zn was the highest in Lokongoma Phase2 (6.34mg/kg) and least in Zanwangi(0.16mg/kg ), Pb was highest in 200Unit and Felele (1.56mg/kg ) and least in Lokongoma Phase1 (1.25mg/kg ),Cd was highest in 200Unit and Felele (0.15 mg/kg) and least in Lokongoma Phase1, Lokongoma Phase2 and Zanwangi(0.13mg/kg ), Fe was highest in 200Unit (1.54mg/kg ) and least in Crowther Memorial and Felele (0.64 mg/kg ) and Ni was highest in Lokongoma Phase1&2 (0.09 mg/kg ) and least in Zanwangi (0.01mg/kg).The accuracy of the results has beencheeked using the standard reference material; SRM (PACS-2). The mechanic workshop soils represent potential sources of heavy metal pollution to the environment. The elevated levels of heavymetals in these soil profiles constitute a serious threat to humans live, surface and groundwater.
TABLE OF CONTENTS
Cover Page i
Title Page ii
Declaration iii
Certification iv
Dedication v
Acknowledgements vi
Abstract viii
Table of Content x
List of Figures xv
List of Tables xvi
CHAPTER ONE 1
1.0INTRODUCTION 1
1.1 Background to The Study 1
1.2 Water 3
1.3Statement of Research problem 5
1.4 Aim 5
1.5 Objectives 5
1.6 Justification for the Research 6
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CHAPTER TWO 7
2.0LITERATURE REVIEW 7
2.1 Heavy Metals 7
2.2 Soil Pollution 8
2.3Natural Occurrences 8
2.4 Origin of Heavy Metals in Soil 9
2.4.1 Geochemical Sources 9
2.4.2 Anthropogenic sources 10
2.5 Water 11
2.5.1Sources of Water 13
2.5.2Wells 13
2.5.3Well Contamination 14
2.6Metal Speciation and Mobility in Soil 16
2.7Forms of heavy metals in soil 18
2.8Effects of Heavy Metals on Humans and Animals 18
2.8.1 Lead 19
2.8.2Cadmium 19
2.8.3 Chromium 20
2.8.4Manganese 21
2.8.5Zinc 22
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2.8.6Copper 22
2.9.0 Soil Physicochemical Properties 24
2.9.1 Soil pH 24
2.9.2Organic Matter 25
2.9.3 Cation Exchange Capacity (CEC) 25
2.9.4 Particle Size Analysis 26
2.10Methods for Heavy Metal Analysis 27
2.11 Sequential Extraction 27
CHAPTER THREE 29
3.0MATERIALS AND METHODS 29
3.1Material 29
3.2Description of Study Area 29
3.3 Sample collection 31
3.4 Determination of Physicochemical properties of soil 32
3.4.1 pH 32
3.4.2 Procedure 32
3.4.3 Determination of Electrical conductivity 32
3.4.4Determination of Organic carbon in soil 33
3.4.5Procedures 33
3.4.6 Determination of Particle Size Distribution 34
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3.4.7 Procedure 34
3.4.8 Cation Exchange Capacity 35
3.4.9 Procedure 36
3.4.10 Determination of Phosphate concentration in soil 37
3.4.11 Procedure 37
3.12Determination of Sulphate in Soil (Agbenin, 1995) 39
3.6.10 Procedure 41
3.6.11 Determination of Cd, Fe, Ni, Pb and Zn by Atomic Absorption Spectrometry 41
3.6.12 Sequential Extraction of Metals (Agbenin and Atin, 2003) 41
3.6.13 Procedure 42
3.6.14 Determination of Heavy Metal in the Well Water (Agbenin, 1995) 43
3.6.15 Procedure 43
3.6.17 Quality assurance validation 46
3.6.17 Preparation of multi-element standard solution (MESS) 46
3.6.19 Spiking experiment 46
3.6.20. Atomic Absorption Spectroscopy 47
3.6.21 Statistical Analysis 48
CHAPTER FOUR 49
4.0RESULTS 49
4.1General characteristics of mechanic workshop soil 49
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4.2 Quality assurance validation 49
4.3 Level of metal concentrations 55
4.4 Pollution Load Index (PLI) 78
4.5Enrichment Factor and Geo-Accumulations Index 78
4.6 Correlation Matrix 78
CHAPTER FIVE 84
5.0DISCUSSION 84
5.2 Heavy Metal Distribution 87
5.3 Indices of Pollutions 88
5.4Enrichment Factor and Geo-Accumulation Index 89
5.5 Geoaccumulation Index 90
5.6Correlation Matrix 90
CHAPTER SIX 91
6.1 Conclusion 91
6.2 Recommendations 91
References 93
Appendices 104
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CHAPTER ONE
1.0 INTRODUCTION
1.1 Background to the Study
The increase in automobile repairs/workshops and their activities in Nigeria are partly due to the ever-increasing demand for personal vehicles, most of which are used “Tokunbo” vehicles. These have contributed remarkably to the problem of soil contamination in most cities. Automobiles used oil (waste) contains oxidation products, sediments, water and metallic particles resulting from machinery wears, used batteries, organic and inorganic chemicals used in oil additives and metals (European Environment Agency, 2007). Soil Percolation of leachates from these materials poses threats to groundwater. Unfortunately, information on the impact of automobile mechanics‟ activities on the ecosystem is still very unavailable. The co-existence of toxic heavy metals and hydrocarbons (HCs) at many of the mechanics contaminated sites all over Nigeria and in other developing countries pose a severe threat to the environment. In fact, the presence of trace elements in soil is increasingly becoming an issue of global concern especially as soil constitutes a crucial component of rural and urban environment (United States Department of Agriculture 2001, Lim, 2008). Heavy metals such as cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn) which are often used as additives in some lubricants and gasoline are non-degradable in the soil. Some of them have been classified as priority pollutants by United State Environmental Protection Agency(United States Department of Agriculture 2001). At the moment, very few technologies, such as soil washing and bioremediation, are available to treat these mixed wastes (Sharma, 2004)
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The problem of soil and vegetation pollution due to toxic metals in spent oil is cause for concern in most metropolitan cities (Vwioko et al., 2006). These toxic heavy metals entering the ecosystem may lead to bioaccumulation and bio magnifications (Wong et al., 2002). Spent oil soil pollution leads to the build-up of essential and non-essential elements in the soil and eventual translocation in plant tissues (Vwioko et al., 2006). Soil pollution by spent lubricating oil has been reported to cause growth retardation/ reduction in plants and this has been attributed to the presence of heavy metals at toxic concentrations in the soil (Anoliefo and Vwioko, 1995). Due to the ever-increasing population and industrialization, most environments are to some extent polluted. It is also estimated that the contributions of metals from anthropogenic sources in soil is higher than the contribution from natural ones, hence, the repeated evaluation of the contamination status of soils (Nriagu, 1988).
Nriagu (1978) reported that we may be experiencing a silent epidemic of environmental metal poisoning from the increasing amounts of metals released into the biosphere. Waste engine oil pollution is responsible for several environmental problems, including disruption of plant water relations having direct toxicity and indirect effects on plant metabolism (Racine, 1994). Edebiri and Nwanokwale (1981) found that metals present in spent lubricating oil are not necessarily the same as those present in unused lubricant. Heavy metals such as vanadium, lead, aluminium, nickel and iron which are low in unused engine oil gave higher concentrations in spent engine oil. Hall (2002) observed that heavy metals, such as copper and Zinc are essential for normal plant growth. There are researches in the Southern part of Nigeria onspent oil pollution of soil and vegetation,
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but not much has been done on spent oil pollution in the North Central region of the country. Consequently, this work is initiated to study and evaluate soil pollution due to heavy metals in spent lubricating oil in the vicinity of some mechanic workshops in Lokoja Metropolis of North Central Nigeria.
1.2 Water
Water, after air, is the most essential commodity to the survival of life. Human life depends to a large extent, on water. It is used for an array of activities; chief among these being for drinking, food preparation, as well as for sanitation purposes. Inasmuch as safe drinking water is essential to health, a community lacking a good quality of this commodity will be saddled with a lot of health problems which could otherwise be avoided (Miller, 1997). Water covers 70.9% of the Earth’s surface, and is vital for all known forms of life. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor and precipitations. Oceans hold 97% of surface water, 2.4% for glaciers and polar ice caps, and, 0.6% for other land surface water such as rivers, lakes and ponds. A very small amount of the Earth‟s water is contained within biological bodies and manufactured products (Wikipedia, 2010).
Groundwater is of major importance and is intensively exploited for private, domestic and industrial uses. According to Ajibade et al., (2011), 90% of the population in Nigeria
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depends largely on hand-dug wells and boreholes. Without water there can be life, Water is necessary for a sustainable economic development of a country. Hand-dug wells are used to complement the usually unavailable pipe-borne water in many communities in a country and this is an indication that water sustains life. Hand dugged wells have been the sources of water for people in Nigeria for ages. Some of this well is dugged in close proximity to rivers. And it is well known that rivers are the major transporting means for different contaminants into groundwater and lakes (Sina et al., 2009). The preference of groundwater as a source of drinking water in rural areas is because of its relatively better quality than river water (Obiri-Dansoet al., 2009). Historically rural settlement was being determined by water source such as stream, river and spring (Okeolaet al., 2010). The inhabitants of these settlements relied on underground water often within a few meters of the surface which they exploited in well digging. Access to safe drinking water is a basic human need and a fundamental human right, crucial for poverty reduction and eradication. According to a report (United Nation, 2003), this situation forces people to consume water directly from the rivers and ponds and this represents a high risk to their health. According to World Health Organization (WHO, 2000), in the next thirty years alone, accessible water is unlikely to increase more than ten percent (10%) but the earth‟s population is projected to rise by approximately one-third. Unless the efficiency of water use rises, this imbalance will reduce quality water services, reduce the conditions of health of people and deteriorate the environment and the world.
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1.3 Statement of Research problem
Lokoja is one of the largest towns in the north central part of Nigeria. It has a population of about 196,643 according to the 1996 population Census. Majority of the people engage in town services such as: Motor cycle, taxi and bus driving as their occupation which has led to the existence of many automobile mechanic workshops almost everywhere in Lokoja town, Also, indiscriminate disposal of their spent oil subjects the soil of thisenvironment to high risk of pollutionwith heavy metals and other harmful substances. Since heavy metals at elevated levels can be dangerous to lives and environment, there is need to check their concentration and mobility in this town. Lack of strict application of environmental protection legislation the need for better control of the pollution situation and absence of basic data about heavy metal pollution from automobile mechanic workshops in the town is the background for the present work.
1.4 Aim
The aim of this research is to evaluate the level of heavy metals and their mobility in the soil and well water of some selected automobile mechanic workshops in Lokoja metropolis, Nigeria. This aim would be achieved through the following objectives.
1.5 Objectives
i. Determination of some physicochemical parameters, such as pH, clay, silt, sand, Electrical conductivity, organic carbon, Cation Exchange Capacity, PO43- and SO42- in the soil sample.
ii. Determination of the concentration of Cd, Fe, Ni, Pb and Zn in the soil sample and well water located within the vicinity of these automobile mechanic workshops.
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iii undertake speciation studies to determine the mobility of the above heavy metals in the vicinity automobile mechanic workshops.
1.6 Justification for the Research
Because of the pollution associated with heavy metal at elevated concentration to humans lives, surface water and underground water in the environment. There is need to ascertain the levels of the heavy metal in this environment. The work is intended to give a base line data for future investigation of activities leading to temporary changes, in concentrations of heavy metals in the vicinity of automobile mechanic workshops in the areas studied (Lokoja). Since no known work of this nature has yet been done in this town.
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