HEAVY METAL STATUS IN URBAN AND PERI-URBAN WETLAND SOILS UNDER VEGETABLE CULTIVATION IN THE BAMENDA MUNICIPALITY CAMEROON
By Godswill A. Asongwe & Bernard P.K. Yerima
Urban and pri-urban agriculture contributes significantly to food security, however it is often endangered by improperly managed wastes. This study investigated the levels, trace sources, and predicted the retention of heavy metals in urban and peri-urban agricultural wetland soils in the Bamenda municipality, Cameroon. Four heavy metals (chromium, manganese, lead and cadmium) were analyzed in 21 randomly collected top soil samples by Atomic Absorption Spectrophotometry. The average concentrations of heavy metals in soil were (35.73 mg/kg) for chromium, (0.08 mg/kg) for manganese, (30.64 mg/kg) for lead and (0.45 mg/kg) for cadmium. The concentrations were generally lower than the maximum WHO permissible levels. The metals had varied origins with significant negative (P < 0.01) correlation relationships between Cr and Mn (r = -0.889, P<0.01), Pb and Cd (r = - 0.455, P<0.05). Two principal component factors explained 84.99 percent of reasons of the existence of metals in the area, while a hierarchical dendrogram yielded three clusters representing a typical rural environment, peri-urban and urban centers, respectively with varying human activities. Multiple linear regression analyses revealed that Pb retention is controlled by pH water, OM and the clay content with an adjusted R value 0.488 which was significant at the 5% probability level. The prediction was markedly increased to 57.2% when CEC was included in the model. Comparatively to Pb, soil properties do not play a major role in controlling the concentration of Cd in the soil.
Keywords: Heavy metal Status. Urban Wetland Soils, Vegetable Cultivation Download