Assessment of Automobile Mechanic Workshop Soils in Lagos and the Genotoxic Potential of the Simulated Leachate using Allium cepa L

This study therefore aimed at assessing the pollution level of the soils from the automobile workshop in Lagos and the genotoxic potential of their simulated leachate using Allium cepa. 2 kg of soil samples were collected at a depth of 0 – 15 cm (top soil) using soil auger from five different points at the automobile mechanic workshop in order to get a representative sample (composite sample) and transferred directly into clean, sterile containers. A control soil sample was obtained from the Botanical garden of the University of Lagos, Akoka. The physicochemical analysis of the soil was also carried out using standard methods. The samples were analysed for lead (Pb), chromium (Cr), cadmium (Cd), zinc (Zn), arsenic (As), nickel (Ni), and mercury (Hg) using inductively coupled plasma atomic emission spectroscopy (ICP-AES) after acid digestion. Aliphatic and aromatic hydrocarbons, TPH and oil and grease were determined. Leachate simulation from the soil was carried out according to the American Society for Testing and Materials. The result showed an obvious influence of automobile workshop activities on the physicochemical properties of soil as well as on the root meristem of Allium cepa. Automobile workshop soil contained significantly higher concentrations for all analysed heavy metals (Cd, As, Cu, Pb, Ni and Zn) in comparison to the uncontaminated garden soil. Cd, Cu and Pb levels were higher than specified regulatory standards. All the leachates concentrations showed one form of aberration: sticky chromosomes, C-mitosis, bridges, lagging chromosomes, binucleate, vagrant cells and micronuclei. The highest aberration occurred in 50% concentration of the treatment while the lowest occurred in the control. The aberrations observed varied with exposure time. The results of the present study showed that simulated leachates from an automobile workshop is genotoxic and mutagenic in the bioassays used in this study. The soils contained heavy metals in higher concentrations than the control and standards set by regulatory authorities. Also, higher TPH was observed too. The observed genotoxicity and mutagenicity are believed to be caused by the leachate constituents.