Gaseous Mercury Exchange Rate between Air and Water Surface over Baihua and Hongfeng Reservoir, Guizhou, China

摘要

Mercury exchange between air and water surface is recognized to be one of the most important processes governing the biogeochemical cycling of mercury in aquatic system. Baihua Reservoir is seriously contaminated with mercury due to anthropogenic activities, while Hongfeng Reservoir does not receive any direct input of wastewater contaminated with mercury. Both reservoirs are alkaline because the bedrocks of their catchments are limestone and dolomite. In order to compare the differences in the biogeochemical cycling of Hg in these two reservoirs, we measured mercury exchange fluxes between air and water surface by using a quartz flux chamber method coupled with high time resolved atmospheric Hg analysis technique. Mercury evasion from water surface is the predominant process at both cold and warm sampling periods, though the average GM emission flux in warm season is significantly larger than that in cold season. The correlations between Hg exchange flux and meteorological parameters showed that mercury flux only correlated significantly with solar irradiation in warm season, and that it only correlated with wind speed in cold season on the other hand, which indicated that the driving force of Hg emission from water in different seasons differed significantly. In general, the emission rate of Hg from Baihua Reservoir is much larger than that from Hongfeng Reservoir.