CHAPTER ONE
1.0: INTRODUCTION AND LITERATURE
1.1: Introduction
Environmental pollution as a result of man’s increasing activities has increased considerably in the past century due mainly to significant increases in economic activities and industrialization. Several studies have shown that heavy metals such as lead, cadmium, nickel, manganese and chromium amongst others are responsible for certain diseases (Wegwu et al., 2002). Metals found in waste dumpsite exist in various forms either as the pure metal or alloyed with various other metals. Heavy metals impairing the quality of the environment come from various sources that can be categorized into urban-industrial aerosols, liquid and solid wastes from animal and man, mining and industry and agricultural chemicals (Wegwu et al., 2002). The disposals of materials contaminated with heavy metals such as in waste dumpsite are of concern and pose dangers to people in contact with the contaminated soils and plants. Research made it known that toxic metals arising from human activities are accumulated in soil. The quality and quantity of solid waste generated in Nigeria vary widely from day to day, season of the year and nature of the waste disposed due to improper waste management (Wegwu et al., 2002). Aboyade, (2004) reported that concentrations of heavy metals in soil around waste dump site are influenced by types of wastes, topography, run-off and level of scavenging. The wastes at dumpsite are usually left over a long time to decompose naturally eaten by animals, picked by scavengers or washed away by floods when it rains into the larger creek and rivers thus affecting the surface water quality (Obute et al., 2001).
Recently, many studies have shown that heavy metals and metalloids with an atomic density >6 g/cm3– from these wastes can accumulate and persist in soils at environmentally hazardous levels (Wegwu et al., 2002). Most abandoned waste dumpsites in many towns in Nigeria attract people as fertile ground for cultivating varieties of crops. The cultivated plants take up the metals either as mobile ions presents in the soil solution through the root or through foliar adsorption. The uptake of the metals by crops results in the bioaccumulation of these elements in plant tissues. This is known to be influenced by the metal species, plant species and plant part (Obute et al., 2001). Indeed, it has been reported that plants grown on soils possessing enhanced metal concentration due to pollution have increased heavy metal ion content. If the consumption of these metals through plant source is not carefully regulated, it may lead to accumulation in man with attendant health hazards.
1.2: Justification of study
Urban areas known for high level of industrial activities generate more pollutants and therefore subject to the menace of resultant indiscriminate disposal of both domestic and industrial wastes. A typical example of such urban centres is Port Harcourt city located in the heart of the oil-rich Niger Delta of Nigeria. There are reports that its suburbs are loaded with toxic heavy metals and certain trace elements resulting from poor waste management programme (Wegwu et al., 2002).
The presence of toxic heavy metals in the environment continues to generate a lot of concern to environmental scientists, government agencies and health practitioners because of health implications of their presence (Awofolu, 2005). Heavy metals have been referred to as common pollutants are widely distributed in the environment with sources mainly from soils and weathering of rocks (Merian, 1991; and O’ Neil, 1993). However, levels of these metals in the environment have increased tremendously as a result of human inputs and activities (Awofolu, 2005). According to Oskarson et al. (1992), there exist transfer of heavy metals from contaminated soil to plants and from plants to animals with the subsequent transfer through the food chain up to man.
It is not uncommon to find ruminants feeding on grasses and birds feed on insects and earthworms on the dumpsite soils. High concentrations of metals in the environment may lead to accumulation, becoming toxic to plants and animals with possible danger to human health.
Solid waste disposal tends to pollute underground water at the vicinity of dumpsites which has been a serious problem for the entire world. It threatens the health and well-being of the residents, plants, and animals. All water pollution is dangerous to the health of living organisms; it has been reported that the quality of the underground water close to dumpsites is compromised resulting in serious health problems to residents. In some areas, the population has only one source of water and if this water is polluted, the population has no choice but to use it (Ince and Howard, 1999). The effect of toxic substances and a wide range of other adverse effects can occur when waste products are introduced into the water body leading to changes in physical, chemical and biological parameters such as infectious agents, temperature, turbidity, color, pH, salinity and oxygen concentrations. Changes in any of these parameters have direct environmental effects and can also produce impact by modifying other parameter.
The role of some heavy metals (Cd and Pb) is very critical in determining the quality of our atmosphere because air, soil and water are directly interacting with each other. Growing heavy metals pollution especially in air has led to increased respiratory diseases, infant mortality and also affects the functioning of the blood, liver, kidney and brain. The measurement of Pb, Cd, Cu, Zn and Ni accumulation in soil and plant appears to be a useful tool for evaluating the potential heavy metal hazards of the environment (Mudassir et al., 2005).
In Nigeria at present, little data is available on the extent of soil-vertebrates-human pollution. Clearly, there is a gap in knowledge related to dumpsite soil-water-animal-human pollution especially in Nigeria and empirical data are needed as the basis for wider modeling assessment. Lagos as an urban settlement with high industrial presence generates tremendous amount of waste which can be toxic to the environment. Most of the waste dumped in the landfills in Lagos is not treated at the point of generation before disposal and this exposes the environment especially the soil, underground water and soil organisms to direct contact with toxic substances.
Heavy metal content of soils is a critical measurement for assessing the risks of refuse dumpsites. Since these contaminants affect the environmental qualities in and around such open dumpsites, monitoring of soil qualities especially heavy metal content in dumpsite becomes necessary which can facilitate to recommend suitable remedial measures.
1.3: AIM AND OBJECTIVES OF THE STUDY
The aim of the study is to assess heavy metal concentration in soil and selected subterranean animals in dumpsites in Lagos State.
Objectives
- To characterize the waste at the landfill
- To determine the level of heavy metal concentration in soil of dumpsites.
- To evaluate the heavy metal concentration level on subterranean animals in dumpsites.
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