The Effect of nutrition status on sediments distribution characteristics of total mercury and methylmercury in Lake Taihu

In order to investigate the effects of nutritional status on the mercury(Hg) distribution and methylation of mercury(Hg) in the sediment in Lake Taihu,total mercury(THg) and methylmercury(MeHg) were determined by PSA and GC-CVAFS for sediment samples collected from areas with different levels of trophic level.The organic matter content in sediment,total nitrogen(TN) and total phosphorus(TP) in overlying water were also measured.The results showed that the average concentration of THg in surface sediment was 62.94ng/g with a range from 32.30 to 150.28ng/g,correlating well with trophic levels.The vertical profile of THg was influenced by anthropogenic activities and organic matter.MeHg concentrations in the sediment ranged from 0.32 to 1.01ng/g with an average of 0.51ng/g.There were no significant differences among MeHg levels in the bay areas with different trophic status.The concerntration of MeHg was affected by organic matter content,with higher levels of MeHg being observed in surface sediment and decreasing with increasing depth until reaching a stable level.The methylation ratio of Hg was low in Lake Taihu,probably due to high dissolved oxygen in water that inhibits methylation process.