梯级水库修建对乌江甲基汞分布的影响

Effect of Construction of Cascade Reservoirs on the Distribution of Methylmercury in Wujiang River

采用蒸馏-乙基化结合（GC-CVAFS）法,测定了2006年乌江流域梯级水库系统入、出库河流甲基汞的含量,探讨了其分布特征和时空变化规律以及梯级水库修建对河流甲基汞分布的影响.结果表明：乌江流域梯级水库系统入库河流水体中ρ（总甲基汞）和ρ（溶解态甲基汞）分别为0.07-0.70和0.03-0.16 ng/L;出库河流水体中ρ（总甲基汞）和ρ（溶解态甲基汞）分别为0.10-0.34和0.04-0.26 ng/L.入库河流水体中ρ（总甲基汞）与ρ（悬浮物）有显著的正相关关系,并且丰水期高于枯水期;出库河流水体中ρ（总甲基汞）在夏秋季节显著高于冬春季节.梯级水库的修建使乌江在多个河段的ρ（甲基汞）升高,并且随着水库生态系统的不断演化,下游河流水体中ρ（甲基汞）有升高的可能.

Methylmercury concentrations of inflows and outflows in cascade reservoirs in Wujiang River were determined by distillation- ethylation （GC-CVAFS） technique in 2006. The distribution and temporal and spatial variation of methylmercury were discussed. The results were as follows： ρ（total methylmercury） ranged from 0.07 to 0.70 ng/L and ρ（dissolved methylmercury） from 0.03 to 0.16 ng/L in inflows. In outflows ρ（total methylmercury） ranged from 0.10 to 0.34 ng/L and ρ（dissolved methylmercury） from 0.04 to 0.26 ng/L. The obvious positive relationship between ρ（ total methylmercury） and ρ （ total suspended matter） was found in inflows, and ρ （ total methylmercury） in high flow was higher than that in low flow. ρ（total methylmercury） in outflows collected in summer and fall were significantly higher than those sampled in winter and spring. The ρ（methylmercury） increased at several sites below reservoir because of the construction of cascade reservoirs, therefore, it is possible that ρ （methylmercury） would increase dramatically with the development of reservoir.