摘要：Formation of reservoirs in a river could result in significant changes in water chemistry and environment risks, but the abundance variability of mercury (Hg) in large reservoir and its influence on the man-made lake Hg cycle were poorly documented. Water samples were collected from the Three Gorges Reservoir (TGR) in the initial stage of dam operation to examine the influence of reservoir operation on Hg delivery and budget of the TGR. The results suggested that the mean concentrations of total dissolved mercury (THg) were 91 ng/L, 74 ng/L, and 89 ng/L in the main channel of TGR, Xiangxi Bay and Daninghe Bay, respectively. Dissolved organic mercury (OHg) was the most abundant mercury in the TGR, accounting for 70% - 80% of the THg (by concentration); while the concentration of dissolved inorganic mercury (IHg) was low and contributed for 20% - 30% of the THg. THg contents increased significantly after 156m impounding compared with prior operation of the TGR. Hg released from flooded soils was one of the main controlling factors of its distribution and outflow in the TGR based on the mass balance approach. Approximately 21% of the outflow THg was added by the TGR flood soils due to the impounding based on a monitoring scheme in 2007, in which OHg was the most part of the added THg due to flooded soil release. Our results suggested that the dam impoundment can enhance the Hg abundance, as well as Hg loading in the TGR, which could have long-term influence on the riverine ecosystem.
