Determination of selected heavy metal concentrations in an oil palm plantation soil

Abstract

Heavy metals occur naturally in soil, but the agricultural, mining and industrial activities could enhance their concentration in soil. The application of chemical fertilisers in the agricultural soil can increase the level of heavy metals. This study was carried out in an oil palm plantation to identify presence of selected heavy metals in soil and estimate the pollution level due to presence of these compounds. The soil samples were collected in triplicates using a hand auger. The samples were then digested and the heavy metals were analysed using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). Geo-accumulation index (Igeo) was used to assess the degree of heavy metal contamination. Heavy metal concentration ranges were as follow: 0.76-2.00 mg kg-1 for Cu, 0.29-1.58 mg kg-1 for zinc (Zn), 0.07-0.22 mg kg-1 for lead (Pb) and 0.01-0.05 mg kg-1 for nickel (Ni). Copper (Cu) concentration was found to be higher than others. The accumulation of Cu and Zn in soil was possibly related to the application of chemical fertilisers. All samples showed Igeo value less than 2, indicating that the soil was uncontaminated. This suggests that the application of chemical fertiliser is still under control. Nevertheless, a comprehensive metal analysis including arsenic (As) and cadmium (Cd), as well as the distribution pattern of metal in the agricultural soil is still required.