ABSTRACT
Automobile junk markets have been observed to be one of the sources of heavy metal pollution in soil and water. The aim of this study is to assess the level of heavy metal pollution within two acclaimed biggest automobile junk markets at Obosi and Nnewi, Anambra State, Nigeria. Twenty four (24) composite soil samples including the background samples at 0-15cm and 15-30cm depths, and six (6) water samples were randomly collected. Samples were properly digested and subjected to spectroscopic analysis using Atomic Absorption Spectrometer (AAS) for trace metals, Physiochemical and Microbiological analysis. The result shows that trace metals concentration (ppm) in 0-30 cm depth are well above the background values with Ni in excess of international standard. Metal enrichment is in the order of Ni> Fe >> Zn > Cu > Mn > Pb > Cr. The pollution load index and contamination factor reveals that the soil around the automobile junk market is at various stages of pollution with heavy metals, ranging from slight contamination to severe pollution. The geoaccumulation index however suggested that the soil is not contaminated. Result also suggested that water around the automobile junk markets are not advisable for domestic uses, as a result of its heavy metal contents, acidity, high turbidity, high salinity and dissolved oxygen as well as the presence of bacteria such as coliform and e.coli which are connected to the effects of industrial waste accumulation and indiscriminate domestic waste disposal as suggested by the principal component analysis.
CHAPTER ONE: INTRODUCTION
- Background Study
Heavy metals are chemical elements that occur naturally and maybe toxic in high concentrations. Excess heavy metal accumulation in soils is toxic to humans and other animals. Heavy metals content of soil are of major significance because of their non degradable nature and ability to accumulate for long period of time (Gallego et al 2002, Wu and Zhang, 2010). Some of these heavy metals like Iron, Copper, Zinc, Cobalt and Manganese are essential to life but can be toxic in high doses (Adepoju-Bello et al, 2009). The environmental pollution concern rises when they are in higher concentration due to natural mineralizing processes and/or human activities. The impact of heavy metals on the environment is a concern to government and the general public (Page and Chang, 1985, Feigin et al 1991, Tiller 1992). Uncontrollable inputs of heavy metals are undesirable because once accumulated in the soil, these elements are generally very difficult to remove and potentially harmful effects that may arise in the future should not be ignored.
The concentrations of heavy metals in soils are associated with biological and geochemical cycles and are influenced by anthropogenic activities such as agricultural practices, transport, industrial activities, waste disposal respectively (Lund 1990). Overload of heavy metals ions in soil environment clearly poses a significant risk to the quality of soils, plants, natural waters and human health (Adraino, 2001). The bioavailability of metal ion in soils is influenced by the temperature, cation exchange capacity, organic matter, competition with other metal ions, composition and quality of soil (Moon et al.2000, Mapanda et al. 2005, Machender et al. 2010). Exposure to heavy metals is normally chronic (i.e over a long period of time) due to food chain transfer. Chronic problems associated with long term heavy metal exposures are: Mental lapse, Kidney problems, skin poisoning, liver problems, gastro-intestinal complications amongst others.
Some industries usually discharge their wastes into the environment with little or no treatment. The automobile industry is one of the producers of industrial pollutants into the environment (Ogbuagu and Ajiwe, 1998). Automobile junks are waste auto engines traded and transferred to developing countries. These waste or knock down engines are recycled and reused or abandoned giving rise to poor waste management (fig1).
The alarming increase in water pollution has been reported in a number of cities throughout the world because of its overwhelming environmental significance. For instance, human exposure to heavy metals has risen dramatically in the last 50 years as a result of an exponential increase in the use of heavy metals in industrial processes and products (Ano et al., 2007). The decomposing nature of industrial discharges, urban storm water runoff and agricultural drainage can pollute surface and underground waters. Crude recycling of used engines and transmission is a major concern to environmental health and safety.
This research work assesses soil and water contamination by heavy metals and microbiology in the vicinity of auto junk market causing soil degradation, water contamination and pollution in the soil, rivers and groundwater across Obosi and Nnewi automobile junk markets in Anambra State, Nigeria.
1.2 Heavy Metal Availability
Soils naturally contain trace levels of metals and heavy metals also occur naturally, but rarely at toxic levels (Estifanos, 2013). The presence of metals in soils, therefore, is not indicative of contamination (Nwachukwu et al, 2013). The concentration of metals in uncontaminated soil is primarily related to the geology of the parent rock material from which the soil was formed. Depending on the local geology, the concentration of metals in a soil may exceed the acceptable ranges. A catchment area containing mineralized rocks will usually have elevated metal levels as the trace metal content of rivers in the catchment area and by their mobility (Olajire and Imeokparia, 2001; Adekola and Eletta, 2007, Nwachukwu et al, 2013). However, mining, manufacturing, and the use of synthetic products (e.g. pesticides, paints, batteries, industrial waste, and land application of industrial or domestic sludge) can result in heavy metal contamination of urban and agricultural soils (Ogbuagu and Ajiwe, 1998). The heavy metals threatening the ecosystem include mercury, arsenic, copper, barium, cadmium, antimony, chromium, lead and zinc (Estifanos, 2013).
Immobilization of metals by mechanisms of adsorption and precipitation will prevent movement of the metals to groundwater. Metal-soil interaction is such that when metals are introduced at the soil surface, downward transportation does not occur to any great extent unless the metal retention capacity of the soil is overloaded, or metal interaction with the associated waste matrix enhances mobility. Changes in soil degradation of the organic waste matrix, change in pH, redox potential, or soil solution composition due to remediation and weathering processes enhance metal mobility (Mclean and Bledsoe, 1992). The concentration of metals in the soil solution, at any given time, is governed by a number of interrelated processes, including inorganic and organic complexes. These processes are oxidation/reduction reactions, precipitation/dissolution reactions, and adsorption/desorption reactions.
In aquatic ecosystems, contaminants are often rapidly removed from the water column via adsorption processes (Opuene, and Agbozu, 2008). Given that heavy metals are not subjected to degradation processes, they tend to accumulate in benthic sediments (Baeyens et al, 1998). However, heavy metals are not necessarily fixed permanently to sediments; rather they may be remobilized via chemical, physical, and biological processes. The geochemical processes that control the metal mobility and its availability are dissolution, adsorption into mineral and organic particles, mineralization, complexation by biogenic or non-biogenic ligands, and subsequent uptake by biota (Kraemer, and Hering, 2004). Once deposited, metals become subject to a variety of physical, chemical and biological processes that could potentially rework them back into the water column. The processes can be both natural (e.g. bioturbation, erosion) and anthropogenic (e.g. land reclamation, dredging) (Lee and Cundy, 2000). Anthropogenic factors are of particular significance in this present study due to indiscriminate large scale dumping of automobile junks.
1.3 Global Perspective
One of the keys to understanding the spatial and temporal distribution of heavy metals within automobile junk markets and their environmental significance is to understand the process within a global context. Heavy metal pollutants are a problem for developing nations across the globe, and as such they have become the focus of a number of studies in recent years; with some key advances in our understanding. Pollution and particularly heavy metal pollution is a serious problem in many parts of the world; whether they are the result of ongoing industrial development such as that in Africa, or a relic signature of industrialization in the west and south China. If informed mitigation policies are to be proposed to deal with the potential future environmental impact of these ‘indiscriminate’ pollutants discharge, it is imperative that we understand not only the concentrations present, but the actual effect they have on the ecology.
Following the wave of global economic recession, automobile wastes, particularly knockdown engines are continually transferred from industrialized nations to developing countries for recycling and reuse. Much as this business has exceeded the permits of the World Trade Organization (WTO) as a type of waste transfer, it has found a place in Nigeria (Nwachukwu et al, 2013). As new genuine automobile spare parts become more and more expensive or unavailable, motorist in developing countries have resorted to the use of fairly used parts sold in junk markets. Container loads of used engines classified as waste in many industrialized nations are now transferred to developing countries where they are refurbished and sold in junk markets. Over the last three decades there has been increasing global concern over the public health impacts attributed to environmental pollution, in particular, the global burden of disease (Laniyan et al, 2011, Onwukeme et al, 2013).
The unprecedented increase in transfer of junk automobile engines and transmissions from industrialized to developing nations of the world may be reciprocated by more automobile junk markets and mechanic villages. As a result, the environmental impacts of automobile junk markets may cause greater concern to land use planning, water resources management, and public health. Topsoil within and around automobile junk markets become heavily contaminated by toxic heavy metals in many parts of Nigeria. Storm water from automobile junk markets gets into the waterways untreated, and there is no protection to both surface and groundwater within and around automobile junk markets. There is also no form of groundwater monitoring wells for safety either by government establishments or by non governmental agencies.
However, the global community is becoming increasingly aware of the values of an ecosystem, as well as the implications of man’s activities on sustainable development; an advocate of a balanced and quality environment (Onwughara et al, 2011). A balanced and quality environment in-turn sustains biodiversity, healthy biophysical domain, promotes socio-economic and public health sectors. In high concentrations, trace metal ions react to form toxic compounds in both flora and fauna cells (Nies, 1999). They are potentially extremely toxic and not only would they affect the biota at a water soluble concentration at less than 1 part per million (ppm), humans can be grossly affected (Asonye et al., 2007). What is yet to be fully known by a generality of the society particularly in the developing world are the ecological and toxicological implications of increased releases and discharges of heavy metals into the environment. The World Health Organization (WHO) estimated that about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution (WHO, 2006).
Nigeria has begun to place a high priority on environmental matters, particularly water-related issues. This is reflected in recent environmental policy, legislation, action plans and programs introduced by the Government. In all these programs, environmental monitoring activities, especially water quality aspects, are given strong consideration. With the creation of the Federal Environmental Protection Agency (FEPA) as the central coordinating body for all environmental matters within the country, Nigeria has evolved a mechanism that will monitor adequately and will keep records of all relevant environmental variables. The new integrated water resources management concept adopted by the government will without doubt, improve all aspects of water use and conservation within the country if the political will and financial resources for the implementation are sustained. Specific regulations to protect groundwater from pollution have also been issued by the FEPA (FEPA, 1991b,c). Industrial sites have to meet concentration limits for their effluents.
For the protection of human health, guidelines for the presence of heavy metals in water have been set by different International Organizations such as United States Environmental Protection Agency (USEPA), World Health Organization (WHO), Environment Protection Agency (EPA), European Union Commission (Marcovecchio et al, 2007; Jim et al, 2004), thus, heavy metals have maximum permissible level in water as specified by these organizations. Maximum contaminant level (MCL) is an enforceable standard set at a numerical value with an adequate margin of safety to ensure no adverse effect on human health (Onwughara et al, 2010). It is the highest level of a contaminant that is allowed in a water system.
1.4 Research Hypothesis
The ever increasing number of automobile junk markets and knockdown engines over a wide geographical spread will constitute a severe environmental problem this millennium, if not properly addressed. For example, the Obosi automobile junk market is situated at about 1Km from the Idemili River at a slope of 10% which facilitates the quick transport of deleterious contaminants to the residential area and the Onitsha urban waterway which on the other hand serve as the primary source of water and aquatic food to Onitsha metropolis (Nwachukwu et al; 2013).
Poor development of automobile junk market is possible to cause significant ecological impact relating to depth, degree, and distance of distribution of metal contaminants in the soil. It is obvious, that trace metal concentration in soils might usually be high near the point source, which will always dispel with both distance and depth owing to increasing limits in mobility and physical dilution. Depth of dispersion accounts for the tendency to groundwater pollution.
1.5 Study Area Description
The study area covered two semi urban towns of Obosi and Nnewi located in Idemili North and Nnewi North local government areas of Anambra state which are faced with the risk of soil and water pollution. Both towns have a high population density of more than 1000 persons per hectare. The population has continued to grow making the city to sprawl toward surrounding villages and smaller towns. The government established automobile junk markets in these villages to reduce the pollution from the activities of mechanics in the city. However, urban development and growth have made the erstwhile isolated automobile junk markets to be crowded by residential buildings. Migrant workers and civil servants working in various institutions and establishments have moved close to the automobile junk markets and the people are now faced with the potential risk of contaminants released from the area.
Obosi is located between latitude 6o 06’ 23.78’’N and longitude 06o 47’57.00’’E while Nnewi is located between 6o 01’13.62’’N and 6o 52’ 52.58’’E as shown in Figures 2 and 3. Obosi is a town in Idemili North Local Government Area and Nnewi is in Nnewi North Local Government Area of Anambra state. The area lies within the humid tropical rainforest belt (Iloeje, 1965). Obosi and Nnewi are influenced by two major trade winds: the warm moist southwest trade winds during the rainy season (April-October) and the north east trade winds during the dry and dusty harmattan (November-March). The average annual rainfall is 1500mm. The temperature is generally high (maximum monthly temperatures varies between 27.2°C and 35°C, the highest between February and March, and minimum temperature varies between 18.2°C to 23°C, the coolest between August and September). The daily mean humidity of the area varies between 40% and 92%.
