ASSESSMENT OF HEAVY METALS IN SOIL COLLECTED FROM DUMPSITES IN AWKA
The study investigated the concentration of heavy metals (Mg, Fe, Zn, Pb, and Cr) present in soil samples collected from dumpsite in Awka using standard techniques. Soil samples from two dumpsites (1 and 2) and a control sample were used for the study. The results revealed higher concentration of heavy metals in samples from the dumpsites than the control. The levels of heavy metals detected were in this order, dumpsite 1> dumpsite 2> control. The levels of Fe and Cr observed in samples from dumpsite 1 and 2 (Fe 94.35±0.013mg/kg, Cr 22.20±0.173mg/kg and Fe 52.87±0.022, Cr 17.40±0.021 respectively) were above WHO maximum allowable limit (20.0mg/kg for Fe and 1.5mg/kg for Cr). The mean concentrations of Mg, Zn and Pb in all the samples were below WHO maximum allowable limit. The order of heavy metal concentration observed in the soil samples were as follows Fe>Cr>Mg>Zn>Pb. These heavy metals in polluted soil accumulate in crops and contaminate edible portions of the plant, thus acts as poison to human.
TABLE OF CONTENT
Title Page i
Table of Contents vi
List of Tables ix
List of Figures x
List of Plates xi
1.1 Justification of the Study 3
1.2 Aim of the Study 4
1.3 Objectives of the Study 4
Literature Review 5
2.1 Concept of Heavy Metal 6
2.1.1 Origin of Heavy Metals 6
2.1.2 Biological Role of Heavy Metals 7
2.1.3 Properties of Heavy Metals 7
2.1.4 Uses of Heavy Metals 8
2.2 Soil Contamination by Heavy Metals 12
2.3 Toxicity of Heavy Metals 14
2.3.1 Environmental Toxicity of Heavy Metals 14
2.3.2 Nutritional Toxicity of Heavy Metals 15
2.3.3 Other Toxicity of Heavy Metals 16
2.4 General Effects of Heavy Metals 16
CHAPTER THREE 22
Materials and Methods 22
3.1 Study Area 22
3.2 Research Design 22
3.3 Soil Sample Collection of Preservation 22
3.4 Materials 23
3.5 Soil Digestion 23
3.6 Preparation of Stock Solution of Standards 24
3.7 Method of Validation 25
3.8 Sample Analysis 26
3.9 Statistical Analysis 26
CHAPTER FOUR 27
4.1 Heavy Metals in Soils from Dump Sites in Awka 27
CHAPTER FIVE 30
Discussion, Conclusion and Recommendation 30
5.1 Discussion 30
5.2 Conclusion 32
5.3 Recommendation 32
LIST OF TABLES
S/N Title Pages
1. Physical Property of Heavy Metals 7
2. Chemical Property of Heavy Metals 8
3. Concentration of Heavy Metals in the Soil Samples 28
Pollution is a worldwide problem and its potential in influencing health of the human population is great (Khan and Ghouri, 2011). The impact of pollution in the vicinity of overcrowded cities and from industrial effluents and automobiles has reached a disturbing magnitude and is arousing public awareness (Begum et al., 2009). The unselective dumping of refuse, discharge of industrial effluents, petroleum wastes and crude oil spills replete with heavy metals give rise to consequences which are of paramount importance to the health of the environment (Joy et al., 2013). These discharged wastes contain heavy metals which, although considered essential macro- and micro-elements especially at non-adverse effect levels (Dimari et al., 2008), may have adverse effects on the population in the concentrations encountered in polluted environments.
Heavy metals are inorganic elements essential for plant growth in traces or very minute quantities. They are toxic and poisonous in relatively higher concentrations (Macdonald and Christopher, 2011). Well known examples of heavy metals include: Iron, Lead and Copper. Others include: Arsenic, Mercury, Cadmium, Chromium, Nickel, Zinc, Cobalt and Vanadium (WHO, 2003). Metals such as copper and zinc are generally regarded as essential trace metals (Nduka et al., 2010) because of their valuable role in the metabolic activities of organisms. However, heavy metals like Cadmium, Lead, Nickel and Mercury exhibit extreme toxicity even at trace levels. Most essential metals have been found to be toxic when supplied in concentrations in excess of the optimal levels (Joy et al., 2013). Metal poisoning arises from heavy metals that have toxic properties leading to adverse effects on human and ecosystem health (Voet et al., 2008). Although acute poisoning from heavy metal poisoning is rare through ingestion or dermal contact chronic exposure to even small doses can be disastrous (Sherameti and Varma, 2010). Chronic exposure to heavy metals leads to accumulation in the food chain which leads to an increased stock in biota, therefore magnifying the human dose (Voet et al., 2008). The chronic problems associated with long term heavy metals exposure include; Serious hematological and brain damage, anaemia and kidney malfunctioning (Sonayei et al., 2009). Heavy metals such as Pb and Cd are lethal even in very small doses. Lead has a negative influence on the somatic development, decreases the visual acuity and auditive thresholds (Simeonov et al., 2010). Acute exposure to lead causes brain damage, neurogical symptoms, brain damage and could lead to death (Simeonov et al., 2010). Cd exposure on the other hand, causes renal dysfunction, calcium metabolism disorders and also increased incidence of some forms of cancer possibly due to the inhibition by Cd of DNA mismatch remediation (Kumar, 2009). Malignant neoplasia and skin ulcers have been reported due to various occupations with exposure to chromium compounds. Chromium (VI) inhalation is responsible for bronchial asthma (Sakar, 2005). Manganese toxicity affects the central nervous system, visual reaction time, hand steadiness and eye-hand coordination (Calkins, 2009).
The most common environmental pollutants in the world are heavy metals (Papatilippaki et al., 2008). The presence of heavy metals at trace level and essential elements at elevated concentration causes toxic effects if exposed to human population (Fong et al., 2008).The knowledge of heavy metal accumulation in soils, the origin of these metals and their possible interactions with soil properties are a priority in many environmental monitoring (Qishlaqi and Moore, 2007). The accumulation of heavy metals in agricultural soils is of increasing concern due to food safety issues and potential health risks as well as its detrimental effects on soil ecosystems (Qishlaqi and Moore, 2007). Food chain contamination by heavy metals has become a burning issue in recent years because of their potential accumulation in biosystems through contaminated water, soil and air (Begum et al., 2009). Heavy metals can accumulate in the soils to toxic levels as a result of long term application of untreated waste waters and fertilizers. Soil irrigated by waste water accumulate heavy metals in surface soils and when the capacity to retain heavy metals is reduced due to repeated application of waste water, heavy metals leach into ground water or soil solution available for plant uptake (Papatilippaki et al., 2008). Research findings indicate that application of heavy doses of fertilizer, pollute ground water by nitrates and heavy metals through leaching and this affects the quality of water (Mico et al., 2006).
The environment has continued to suffer from pollution due to increased population and industrialization (Goel, 2009). On the other hand resources like land have remained constant leading to overcrowding of population around towns and main cities. The biggest challenge resulting from this overcrowding is waste disposal. The overcrowding has led to domestic and industrial wastes being disposed of on lands and this has led to the contamination of soil, especially from heavy metals (Lesamana, 2009). In Awka, the rapid urbanization, improper waste disposal and use fertilizer in farming activities could be a source of heavy metal contamination in the soil.
However, in spite of the very hazardous nature of heavy metals in the soil, studies of these metals in Anambra environment are scanty. Also, it is known that the bioaccumulation of concentrates metals in some food species may be hazardous to human health, therefore knowledge of the concentration of metals existing in any terrestrial ecosystem is necessary.
1.1 Justification of the Study
There is need for better understanding of soil quality, soil pollution, and soil pollutants in other to protect our health, and also the health of the ecosystem. The presence of heavy metals in the soil can be toxic to humans, requiring costly treatment of soil. This study helps us understand how heavy metals can affect soil quality, soil organisms and human health. It also reveals the sources of soil pollution by heavy metals and the environmental hazard soil contamination can cause.
1.2 Aim of the Study
This study aims at assessing the heavy metals on soil samples collected from refuse dump sites in Awka, Anambra state. It attempts to provide a baseline data upon which future computations of the soil quality (in Awka) as a result of increased anthropogenic activities and urbanization would be based.
1.3 Objectives of the Study
The objectives of the study including the following:
• To perform laboratory analysis of the soil samples collected from refuse dump sites within Awka.
• To characterize the heavy metals present in the soil samples collected.
• To determine the levels of concentration of the heavy metals discovered in the soil samples.
• To proffer recommendations that would help reduce the rate of heavy metals contamination of soil in Awka.
• To compare the rate of the heavy metals detected from the dumpsites with the maximum allowable limit
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