Gaseous mercury exchange rate between air and water over Baihua reservoir, Guizhou, China during cold season

Field measurement campaigns over lake water surface at Baihua reservoir in Guiyang, Southwestern China were conducted to measure mercury flux using a dynamic flux chamber technique coupled with automatic mercury vapor-phase analyzer from October 30 to November 4, 2001. The dynamic flux chamber is made of quartz glass, and has low blanks. Water samples were collected, and dissolved gaseous mercury (DGM), reactive and total mercury concentrations in water were measured using gold trap pre-concentration and AFS detection method. Meanwhile meteorological parameters, such as wind speed, wind direction, intensity of solar radiation, air and water temperature, and relative humidity were monitored using a portable weather station. Water surface is a net atmospheric mercury emission source even at cold season (autumn), and the average mercury emission rate is 3.0 ng m(-2) h(-1). We observed a strong correlation between wind speed and mercury emission rate, suggesting that strong wind facilitate mercury evaporation process from the water system during cold season. No significant correlations between Hg emission rate and solar radiation, water and air temperature were obtained.