speciation of heavy metals in the sediments of former tin mining catchment

the chemical speciation of heavy metals (arsenic, chromium, copper, lead, zinc and tin) in the sediments offormer tin mining catchment bestari jaya, peninsular malaysia was determined by using the latest version of the community bureau of reference, usually called the bcr 3-step sequential extraction procedure. furthermore, a fourth step was introduced for digestion and analysis of the residue. the analysis of total metal content was carried out by using microwave acid digestion. the percentage of each metal obtained from the 4 step extraction (acidsoluble + reducible + oxidizable + residual) is in good agreement with the percentage of total metal content obtained from microwave digestion, which implies the accuracy of the procedure. the degree of pollution in catchment sediments was assessed using geoaccumulation index igeo and pollution intensity ipoll. the results indicate that (1) the sediments have been polluted with arsenic (8.8%), chromium (12.9%), copper (17.4%), lead (19.5%), zinc (14.9%) and tin (33.8%) and have high anthropogenic influences; (2) the calculation of geoaccumulation index suggests that catchment sediments have the background concentration for all studied metals (igeo < 0); (3) high ipoll showed that all of these heavy metals pose high environmental risk. (4) the mobility order of metals in sediments at s1 and s2 was sn>pb>zn>cr >cu >as, whereas at s3, s4 and s5, cu>pb>zn>cr>sn>as; in conclusion, acidic ph, total organic carbon, scavenging ability and co-precipitation (inclusion, occlusion and adsorption) of studied metals with non-metals could account for change in the geochemistry of the catchment sediments.