Heavy Metals Profile of Challawa River Basin around Challawa Industrial layout, Kano and It’s Implications for Cultivated Vegetables

Challawa industrial layout is one of the three major industrial areas of Kano. This study was undertaken to assess the heavy metal profile of Challawa River basin around Challawa industrial area and its implication for cultivated vegetables. Lead, cadmium, chromium and zinc concentrations were analyzed using Shimadzu atomic absorption spectrophotometer (model AA-6800, Japan) after wet digestion. The range of concentrations (mg/kg) of these metals was: Pb (94.46-104.76), Cd (11.43 - 26.46), Cr (163.98 - 201.46) and Zn (154.98-254.46). The significant differences observed in soil metal levels between the control and the study area suggests that Challawa industrial area has a significant influence on the heavy metal profile of the basin. The results indicates that the study area does not pose significant health/environmental risk with respect to lead, chromium and zinc intoxication even though the mean soil lead level was found to be above Dutch Target value (85 mg/kg) which is the bench mark for soil quality. However, cadmium was seriously implicated in the study as the mean soil cadmium concentration was found to be above the United States Environmental Protection Agency (USEPA) Maximum Permissible Limits (MPL) and the European Regulatory Standard of 3.00 mg/kg. There is therefore a serious cause for concern as uptake by cultivated vegetables cannot be completely ruled out. Determination of the chemical form (speciation) of these metals in the basin is hereby recommended to evaluate their mobility and bioavailability.