Research On Heavy Metal Fraction And Bioavailability In Top Soils Of Different Function Areas Of Qingdao

This article studied the concentration and chemical speciation distribution of heavy metal in Qingdao city soil .And the effect of physical and chemical properties on soil heavy metal distribution was further explored.At the same time,based on the analysis and assessment of heavy metal content in vegetables,bioavailability of heavy metal was studied by using total mensuration and chemical extraction method.Main conclutions of the study are as follows:1.The mean content of Cu,Zn,Pb,Cd in urban top soil was respectively 44.842mg/kg,151.851mg/kg,40.163mg/kg and 0.978mg/kg.There were quite changes of heavy metal content in the soil of different function areas.The content of Cu,Zn,Pb,Cd is respectively3.1,3.6,3.7 and 24.5 times of the Jiaodong peninsula background value. Hakanson's potential ecological risk assessment was used to assess the potential ecological risk of heavy metal in urban soil of different function areas. And the ecological hazard index is industrial district > inhabited area > scenic spot > business district> agriculture area.2.The general distribution trend of chemical speciation was obtained by using the Tessier extraction process.The sequence of different forms of Cu was bount to residual fraction> organic phase > Fe-Mn oxides >carbonates> exchangeable form. The sequence of Zn was residual fraction> Fe-Mn oxides> organic phase >carbonates> exchangeable form. The sequence of Pb was residual fraction> Fe-Mn oxides> carbonates> organic phase > exchangeable form.The sequence of Cd was residual fraction> organic phase > Fe-Mn oxides > exchangeable form >carbonates. The different content and physicochemical parameters had different influences on the chemical speciation of heavy metal. The principal influencing factors and secondary factors were determined using stepwise regression and grey-relational analysis.3.The heavy metal content except Pb in vegetables did not exceeded the nationnal food hygienic standard .Therefore the vegetables concentrate ability to Pb is stronger than other heavy metal. The total mensuration, the Tessier extraction process, the HCl extraction process, the EDTA extraction process and the CaCl2 extraction process were used to study the heavy metal bioavailability of vegetable plot soil.It indicated that the heavy metal bioavailability has high correlative with the extractable heavy metal determined by HCl extraction method and EDTA extraction method.