Environmental Geochemistry Evaluation Of Heavy Metal Elements In Sediments From Middle Reaches Of Minjiang River

Based on the project"the impact of great earthquake of WenChuan on the mines and their surrounding farmland"which is the subproject of State Environmental Protection Department's Emergency Project"Environmental Safety Assessment and solutions of post-great earthquake of WenChuan", the heavy metal elements in sediments which from Middle reaches of Minjiang River was employed to research the geochemistry distribution. Distribution characteristics of Heavy metal elements in sediments in each tributary in the Middle reaches of Minjiang River and the river which flowed into Minjiang River called Daduhe river were studied, correlation analysis, cluster analysis and factor analysis were used to study the relationship among heavy metal elements in sediments and those elements'sources, and in the last three common methods and two evaluation criterions were implementing to evaluate the environmental quality of heavy metal elements in sediments which from Middle reaches of Minjiang River. Some of the conclusions were below:In the Wenjinjiang-Xihe River basin and Chujiang-Xiejianghe River basin, high level regions of Cd,Hg,Pb and Zn almost around Triassic Period coal mine. In the Daduhe River the high level regions were near the lead zinc ore and phosphorite, and the level of heavy metal elements in this reach were several times over other rivers. The levels in other study area increased mostly by human activity affected, thus come up to exceptional fluctuation.The content of heavy metal elements after each river confluxes were the middle value before the rivers conflux, the accordant junction have noticeable effect on the level of heavy metal element in the water.The correlations of heavy metal elements from the sediments in the Wenjinjiang-Xihe River, Chujiang-Xiejianghe River and Daduhe River were analyzed, and in Wenjinjiang-Xihe River, Cd,Hg,As and Cu had good correlation; in Chujiang-Xiejianghe River, Cd,Hg,As,Cu and Pb behave good correlation; in Daduhe River, Pb and Zn come up to positivecorrelation.Three common methods which were Index of Geoaccumulation, Pollution Load Index and the Potential Ecological Risk Index and two evaluation criterions which were national sediments evaluation criterion and global shale average value evaluation criterion were implementing to evaluate the environmental quality of heavy metal elements in sediments which from Middle reaches of Minjiang River. The result base on national sediments evaluation criterion was higher than in the evaluation criterion of global shale average value. And the results of the three evaluations were similar, Middle reaches of Minjiang River classified into low-moderate contamination, and Daduhe River was high-extremely contaminated.In the last, the sources of heavy metal elements were studied. The heavy metal elements from the sediments in the Middle reaches of Minjiang River mostly came from the waste water caused by mining along the river, Pb and Zn in Daduhe River has gone far beyond the standard level and this have something to do with the favorable metallogenic conditions of lead and zinc mine.