Contamination And Potential Risk Evaluation Of Heavy Metals In The Major River Basin Of Hunan

Heavy metal pollution in soil has become more and more severe. It has threatened the food safety, people's health and the environment, especially the watershed soil, which has seriously impacted the local economy, as most of the river areas are well developed and industrialized with a high population density. So the research on conducting the assessment on heavy metal polluted soil and remediation technology has its significance scientifically and practically.By investigating the contents of heavy metals as As,Cd,Pb,Zn,Cu and Cr as heavy metal content in soil of Xiangjiang,Zijiang,Yuanjiang and Lishui River basins of Hunan province, evaluating them by taking the ways of single pollution index and comprehensive pollution index. An indoor siol columination eluviation experiment was carried out to investigate the sole effects and comprehensive effects of red mud, bone char and phosphorite on speciation transformation of As,Cd,Pb,Zn,Cu,Ni and Cr. Our results showed as followes:(1). Investigated the contents of heavy metals in soil of Xiangjiang,Zijiang,Yuanjiang and Lishui River basins of Hunan province, 72, 43, 36 and 19 soil samples have been taken respectively with the volumes from 0 to 20 centimetres from Xiangjiang, Zijiang, Yuanjiang and Lishui, 170 soil samples in total with the principle of taking samples every 5 kilometres along the watersheds. The testing index are As, Cd, Cr, Cu, Zn, Pb and Ni.(2) The soil assessment: Xiangjiang is obviously much more polluted than the other 3 waterbodies. Zijiang, Yuanjiang, and the index in Lishui is lower than the standard so that it is seemed as clean. Cd is the most important heavy metal pollution among As, Cd, Cr, Cu, Zn, Ni and Pb, which exceeds the limit by 88.64%, with a heavy pollution proportion of 9.09. The less important pollution is As, which exceeds the limit by 22.22%. Other chemical elements are rare.(3) TCLP ecosystem assessment on the 4 waterbodies: there is high correlativity between the extracted heavy metal bioavailable form and the content of heavy metal in soil. All of the 4 waterbodies are in security level by Nemerow method. The pollution in Xiangjiang is the most polluted, with the proportion of heavy pollution being 18.30. The ratio that the security level is apparently higher than it is in heavy polluted level in Zijiang, Yuanjiang and Lishui.(4) The impacts of the mobility of heavy metals that the 3 chemical addictives (bone char, red mud and powdered rock phosphate) caused: the mobility of As has notably increased after bone char, red mud and powdered rock phosphate being added in 3 soil samples; the mobilities of Cd, Cr, Cu, Zn, Ni and Pb have reduced significantly. The come outs for the 3 chemical addictives are not differed.