Speciation of Nickel, Lead and Cadmium under Different Soil Land Uses of Lesser Himalayas

Speciation of heavy metals in soils were analysed under different land uses of Lesser Himalayas. The soil samples were subjected to Tessier sequential extraction with some modifications. Results indicated abundance of residual fraction indicating lithogenic origin. Cadmium was not detected in water soluble, exchangeable, carbonate and organicfractions while Pb was present in all fractions except water soluble. Assuming mobility and bioavailability, metals are related to their solubility and geochemical forms and decreased in order of extraction: Cd (79%) > Ni (52%) > Pb (45%). Cd was more mobile and bioavailable, so potential risk on food security and human health. pH had significant positive correlation with oxide-Ni (r = 0.367) and carbonate-Pb (r = 0.366). Organic-Ni was positively (r = 0.431) while oxide-Ni was negatively correlated (r =-3.90) with OC. Calcium carbonate had significant correlation with carbonate-Pb (r = 0.526).