乌江中上游新建水库水体甲基汞的时空分布

为了弄清新修建的水库是否造成水体甲基汞浓度升高，以贵州省乌江流域2座新建水库洪家渡水库和索风营水库为研究对象，采用蒸馏 乙基化结合（GC CVAFS）法测定了不同季节水库水体中甲基汞的浓度，最低检出限为 0.009 ng/L。探讨了水质参数对甲基汞分布的影响以及水库水体甲基汞的分布特征。结果显示:洪家渡水库总甲基汞浓度夏季平均值为 0.11 ng/L，秋季平均值为 0.08 ng/L，冬季平均值为 0.10 ng/L；索风营水库总甲基汞浓度夏季平均值为 0.11 ng/L，秋季平均值为 0.07 ng/L，冬季平均值为 0.09 ng/L。数据表明2座水库水体甲基汞含量均较低，低于目前我国环境质量标准规定的一类地表水汞含量标准限值，与世界上其他未受污染的水体基本相当。水库水体甲基汞浓度随水体深度的增加没有明显的变化规律，且夏季略高于冬季、秋季，这与夏季降雨量和温度有关，在入库处与大坝前没有明显的变化趋势。这与水库中被淹没土壤有机质含量偏低且流域内基岩为碳酸盐有关，还与其他环境因素有关(如pH值较高，DOC含量偏低等)。通过研究发现目前库区环境汞的甲基化率低，但随着水库生态系统的不断演化，内源和外源营养物的输入及水体在温度分层其间自身甲基汞的形成，导致水体甲基汞含量的逐渐增加，但仍需进一步的研究证实。

SPATIAL AND TEMPORAL DISTRIBUTION OF METHYLMERCURY IN TWO NEW RESERVOIRS ON THE UPPER COURSE OF WU JIANG RIVER

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.