Heavy Metal Pollution in Surface Dust From Urban Squares in Suzhou, China:Total Concentrations, Speciation Analysis and Health Risk

An investigation of thirty dust samples collected form five squares in Suzhou was performed to analyze the concentrations and speciation distribution of heavy metals by ICP-OES and Tessier sequential extraction procedure, and to assess the associated human health risks, using the health risk assessment model (USEPA). Compared with the environmental background and existing standard, higher pollution level of Cd, followed by Pb, Cu and Cr, were recorded. Speciation analysis showed that Cu was abundant in the oxidizable (F4) and residual (F5) fractions, Pb was associated with the reducible (F3) and residual (F5) fractions, more than 90% of Cr existed in the residual fraction (F5), while Cd was mainly dominated by the reducible (F3) and acidsoluble (F2) fractions. Mobility factors (MF) of the four metals were followed the order of Cd>Pb>Cu>Cr. The results of exposure risk assessment indicated incidental ingestion of dusts was the dominant exposure route to local residents, Cr and Pb were the major source of health risk caused by exposing to square dusts. Both the calculated non-cancer risk (HI) and the carcinogenic risk values were all below the risk limits recommend by USEPA, suggesting little probability of posing health risk. However, children were found to be more vulnerable than adults, and their exposure risk value had reached 5.75×10^-1, which should be paid more attention.