Proposal：Natural Scientific Foundation of China Investigator：Changzhou Yan Periods：2013.01-2016.12 Abstract: In our country, many regions are faced with not only arsenic pollution, but also eutrophication. Both of lake eutrophication and environmental geochemistry of arsenic have become a reseach focus in the field of environmental sciences in recent years. Aimed at lake eutrophication and arsenic pollution, the studies on the influence mechanism of eutrophication and algae bloom on transportation & transformation of arsenic in sediment were carried out, with taking arsenic biotransformtion (methylation) as breakthrough point. The main topics of this project are as follows: (1)the distributional charateristics of arsenic species in overlying water and sediment from lakes of different trophic status, and its correlational study between arsenic speciation distrbution and eutrophication and environmental factors; (2)studies on effect of algae bloom on exchange fluxes of different arsenic species at the sendiment-water interface by field sampling and monitoring to identify the relative contribution of arsenic species release from sediment to overlying water; (3)with a dominant species (blue-green algae) in Lake Taihu as the object of study, studies on the characteristis of toxic, accumulation and biotransformation of arsenic by algae, to explore the key influence factors and regulatory mechanisms of algae biotransformation of inorganic arsenic.This project is very important and meaningful,and will contribute to realize environmental geochemistry of arsenic, predict its ecological risk, and guarantee the health of lake ecosystem and the safety of drinking water sources.