Chemical Fractionation And Bioavailability Of Heavy Metals In Sewage-Irrigated Soils From Xiaoqing River

With the rapid growth of the global economy and the advance of the living standard, the constant expansion of industrial production and the rapid development of urbanization occupied a large number of irrigation water. Then the agriculture irrigation had to use sewage water to irrigate. However, because of our low processing capacity and lack qualified technical personnel, a large number of untreated water was used to irrigate soils, which containing much heavy metals enter into the soils. Because of the accumulation of these heavy metals, heavy metal pollution in soil has received increasing attention. So, the biological activity and environmental actions of heavy metals in soils are not only related to their total amount but also related to the chemical speciation of heavy metals in the environment. The migration, bioavailability and toxicity of heavy metals in soils are all related to their existence patterns. Therefore, the study of heavy metals in the soil is of great significance for understanding their change version, migration law and the role of biological poisoning.In this paper, the superfical soil samples (0-20cm) of the soil types from irrigated soils of Xiaoqing River in Jinan surrounding areas were regarded as research object. Eighty samples of sixteen soil types were collected. The soil samples were treated with total quality dispel and BCR procedure to acquire dates, and four different solutions were gained. The purpose of the procedure was to research the contents and distrrbution of different heavy metals Cd、Cu、Hg、Ni、Pb、Zn、As and Cr in the soils. The distribution character and the pollution source of heavy metals Cd、Cu、Hg、Ni、Pb、Zn、As and Cr were discussed. And the pollution influence of heavy metals in the soils of of Jinan and its surrounding areas were elementarily estimated.The results showed as follows:(1) The date of Ni、Pb、Cu、Cr、Hg、As、Zn、Cd showed that the content of sewage-irrigated areas were higher than the control points. Except the element Cd and element Hg in some samples, the other elements were not over the second national standard. The order of the total content of different heavy metals in soil is:Zn>Cr> Cu>Ni>Pb>As>Cd>Hg.(2) The results indicated that Ni、Pb、Cr、Hg、As、Zn in the main soil types of Jinan and its surrounding areas were dominated by the residual fraction, while element Cd was dominated by the acetic acid extractable fraction with72.2%. The percentage of active fraction of Cd was11.41%. The order of the active portion of different heavy metal in soil is:Cd>Pb>Cu>Zn>Hg>Ni>As>C. The dates showed that the active fractions of sewage-irrigated areas were higher than control points.(3) About the date of RAC of Ni、Pb、Cu、Cr、Hg、As、Zn and Cd, its higher in the sewage-irrigated areas than the control points. The highest date is Cd, which date was37.31, while the lowest date was0.05belonging Hg.(4) The evaluation results showed that the water in Xiaoqing River had somehow pollutied by sewage-irrigated or humane beavier. The elements of Cd、Ni、Pb、Cu As had reached warning admonish while the Cd reached heavy polluted grade. The outcome was related with sewage-irrigated、using pesticide、commercial production and the discharge of car exhaust.