Heavy metal soil contamination in cocoa plantations in South West Region, Cameroon

The status of heavy metal contamination of surface soils in two cocoa plantations of approximately 30 years in Cameroon was evaluated. The bioavailable fractions of Fe, Cu, Zn, Cd and Cr were used to assess the extent of heavy metal contamination using a selection of contamination indices. In addition, other physicochemical properties including organic matter, particle size, CEC and pH were assessed. One of the farms was dominated by sand (64.56 - 73.46% sand) in contrast to the other (2.56 to 37.51%) and the latter had a higher clay content. The order of abundance of heavy metals, as expressed by the mean values, is as follows: Fe > Cu > Zn > Cr > Cd in soils from the two areas. Contamination factors of Cu-, Zn- and Cd are considerable for clay-dominated soil. The potential ecological risk of the metals in both soils was low with the exception of Cd in the clayey soil. Results for hazard assessment showed Cu levels were within the low ISQC sediment criteria in the clay-dominated soil; possibly linked to the long-term application of Cu-fungicide.   Key words: Heavy metal, contamination indices, cocoa plantation, Cameroon.