RESUMO
Sequential extraction procedure was applied to determine the chemical forms of heavy metals in sediments in order to assess their mobility and availability in the aquatic environment. The mean concentrations of Cr, Ni, Pb, Cd, Cu and Zn in exchangeable and carbonate fractions were 14.9, 30.9, 17, 0.37, 4.4 and 14.4mg/kg, respectively. Based on the sediments quality guidelines (SQGs), the adverse biological effects caused by Ni, can occur frequently across the study area. Risk assessment code (RAC) suggested that the Cd has the highest level of environmental risk compared with other studied metals. Modified risk assessment code (mRAC) demonstrated a high potential adverse effect in the many of sampling sites. According to the fractionation results, the concentration of Ni in exchangeable and carbonate fractions was very considerable and more than other metals, hence, the potential risk of nickel release can be much more than other investigated metals.
