Heavy Metal Content in Soils and Vegetables Grown in an Inland Valley of Terengganu and a River Delta of Kelantan, Malaysia

摘要

Heavy metal concentration in vegetables grown in an inland valley of Terengganu and a deltaic area of Kelantan are compared. The presence of heavy metals as indicated by speciation of Fe, Mn, Pb, Cr, Cu, Zn and Cd are discussed. Vegetable farm soils in Terengganu and Kelantan are acidic, sandy and contain a fair amount of organic carbon. Most of the soil Fe is highly concentrated in the RR fraction in the form of mottles of iron oxide and coatings on the sediment surface. Manganese is highly concentrated in the AR fraction, followed by its occurrence in the OO fraction. The study showed the presence of precipitates of Mn-oxyhydroxides and the association of Mn with soil organic carbon. The rest of the heavy metals (Pb, Cr, Cu, Zn and Cd) studied were significantly concentrated in the OO fraction suggesting the great affinity of these metals to the organic carbon in the soils. The fair amount of organic carbon present in the study area might possibly be attributed to litter constituting plant materials and poultry manure-amended soils in the vegetable farms. Despite the low concentration of Pb in the available form (ELFE fraction), its accumulation in the plants could have occurred because of the Pb-organic complexes in the soil. The accumulation of Cd in the soils could be attributed to the presence of available Cd (ELFE fraction) in the soils.