Abstract:

In order to find out whether methylmercury concentrations will increase by building new reservoirs,this study concerns two new reservoirs (Hongjiadu and Suofengying Reservoirs) built in Wujiang River in Guizhou Province.Methylmercury concentrations of different seasons in the water columns about these two reservoirs were determined by distillationethylation GCCVAFS technique,the minimum level has been established as 0.009 ng/L.Influences on the distribution of Methylmercury from water quality parameters and the characteristic of methylmercury in the water columns were discussed.The results were as follows：For Hongjiadu reservoir,in summer total methylmercury concentrations averaged 0.11 ng/L,in autumn averaged 0.08 ng/L,and in winter,averaged 0.10 ng/L;For Suofengying reservoir,in summer total methylmercury concentrations averaged 0.11 ng/L,averaged 0.07 ng/L in autumn,and averaged 0.09 ng/L in winter.The results showed that methylmercury concentrations were relatively low in the water columns,and below the limits for Chinese environmental quality standards.Methylmercury levels were comparable to data reported in other uncontaminated reservoirs.It indicated that methylmercury concentrations in the water were no change with depth.In summer the methylmercury concentrations were higher than in autumn and winter,as a result of higher temperature and more rainfall.At the same time,low methylmercury levels may be due to a low concentration of organic matter in submerged soil and other environmental factors (eg.higher pH concentrations and lower DOC concentrations).Lower mercury methylation was expected in these two reservoirs.With the development of reservoir,it is possible that the methylmercury concentrations will increase due to autochthonous and extraneous organic materials,and methylmercury may be released due to thermal stratification.But this was not confirmed.

Key words: new reservoir/Hongjiadu/Suofengying/Methylmercury