Speciation of heavy metals and Pb stable isotope signatures in urban channel sediments in Nanjing.

In order to investigate the mobile potentiality and the characteristics of heavy metal contamination sources in urban channel sediments,samples were collected from urban channels in residential areas and shopping centers in Nanjing.Speciation of heavy metals was performed by the modified BCR sequential extraction(three-step) procedure,and Pb stable isotope ratios were determined using Inductively Coupled Plasma Mass Spectrometry.Results showed that Cd and Zn were predominantly associated with the acid extractable metal fraction,Pb and Cu with the oxidizable metal fraction,and Ni and Cr with residual metal fractions.Cd and Zn had the greatest environmental effects,while Ni and Cr had the smallest.The range was 2.1024-2.1239 for 208Pb/206Pb and 1.1593-1.1845 for 206Pb/207Pb.The ratios of Pb stable isotopes in the residential area and the shopping center were similar and consistent with those in samples from atmosphere and soils in literature in Nanjing,suggesting that they may have similar Pb contamination sources.