Arsenic(As)is a highly toxic element which has raised serious concern to human health.The occurance of heavy metals in lacustrine ecosystem has been intensively documented,however,the partition of heavy metals like As between different phases in lake water body is still largely unknown.This study aimed at exploring As distribution between the water phase and particle phase as well as the potential influencing factors,including water physic-chemical properties,phytoplankton distributions and seasonal changes.Surveys were implemented in three typical lakes as Taihu,Chaohu and Dianchi Lake during May to December 2013.The collected water samples were analyzed with total As in unfiltered and filtered water,contents of As in SPM,the phytolankton distribution,the total and dissolved nitrogen and phosphorus,and other water quality parameters.The result shows that concentrations of dissolved As in the lake water were in the range of 0.82-7.92μg/L in the three lakes,with the maximum occurred in Dianchi; while total As concentrations in the lake water ranged from 0.18μg/L to 37.96μg/L in three lakes,with the maximum occurred in Taihu.Arsenic partition coefficients in the three lakes are in the range of 3.194-6.282,demonstrating strong adsorption ability of suspended matter on As.The spatial analysis showed that dissolved and total As was well as the As partition coefficients in the three lakes had the same variation pattern,suggesting anthropogenic input contributed mostly to As in lakes.Correlation relationship were observed between partition coefficient and total As,particle-phase As,and a a negative correlation between partition coefficient and dissolved As,ss,Chl-a,TDN,TP.According to spatial distribution characteristics of algae in three lake,it can be inferred that As enrichment ability of Crytophyta,Bacillariophyta and Chlorophyta is higher than Cyanophyta.In Taihu lake,the dissolved and total As As in winter were much lower than those in summer,while little difference was observed for As partition coefficients between the two seasons.Based on correlation analysis,spatial distribution and seasonal variation,it can be infered that increase of Cyanophyta in summer will reduce the partition coefficient of As,resulting in an increase of dissolved As.Eutrophication of lakes had a negative effect on the partition coefficient.