Assessment of Heavy metal concentration in storm runoff generated at Alabata mechanic village, Camp, Abeokuta, Ogun state, Nigeria.

Water is a vital source of life essential for survival of all living organisms. Surface runoff and soil may become contaminated by the accumulation of heavy metals deposited by the activities of auto mechanic village. Runoff samples were obtained during rainfall from Alabata Mechanic Village located at Camp, Abeokuta, Ogun state; during the establishment of peak rainfall (May and June) and cessation of rainfall (November and February). This study examined runoff samples to quantify the concentration of heavy metal within this workshop. Atomic Absorption Spectrophotometer (Buck scientific model 210) was used for analyzing the digested runoff samples for heavy metal content. Mean concentrations of the selected heavy metals in the runoff during establishment of peak were 2.24, 430.65, 1.96 and 6.94 mg/l for Pb, Fe, Cu and Zn respectively but Cd was not detected. While during cessation, the mean concentrations were 0.01, 6.93, 605.43, 3.12 and 12.57 mg/l for Cd, Pb, Fe, Cu and Zn respectively. On average, the runoff sample obtained during cessation had about 100, 72, 64, 61 and 58% more Cd, Pb, Zn, Cu and Fe respectively, compared to the establishment of peak rainfall runoff samples. Pearson correlation shows that there is a positive correlation among the concentrations of all the assessed paired heavy metals except between Cd and Fe for which there is no correlation. All assessed heavy metals have their mean concentrations above the World Health Organization (W.H.O) permissible limits for both sampling periods except for Cu that has mean concentration within the limit during the establishment of peak. Fe has the highest mean concentration for both sampling periods and only it can be regarded as a threat to public health, since the concentrations of other elements are negligible due to dilution action, when they get into rivers or infiltrates into groundwater body.