Grain-size distribution and chemical speciation of heavy metals in Chinese street dust

Abstract

In order to assess the grain-size distribution and chemical speciation of heavy metals, 34 dust samples were collected in the city of Wuhu. Heavy metals concentrations in street dust of different districts varied greatly. Zn concentration in the traffic district, for example, is more than two times that of other districts, and Cu concentration in the industrial district is more than three times that of other districts. Zn mainly comes from traffic sources, and Cu mainly comes from industrial emissions sources. The highest concentrations of Cu and Cd appeared in the particle size of < 75 μm, and the other heavy metals appeared in the particle size of 96-75 μm. Heavy metals concentrations for different speciation appeared in an increasing trend with a reduction in particle size. Zn and Cd were mainly bound to acid-extractable state. Cr, V, Ni, and Co elements were mainly bound to a residual state. Cu and Pb were mainly bound to an organic state. The grain size fraction loads (GSFLoad) of different chemical speciation were mainly high in fine particles. The biological mobility of heavy metals in street dust decreased in the order of Pb (91%) > Cu (85.6%) > Zn (85.24%) > Cd (78.3%) > Co (49.3%) > Ni (39.3%) > V (23.7%) > Cr (20.19%). Bioavailability of Cu emitted from industrial sources was high.