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.