Air/water exchange of mercury in the Everglades II: measuring and modeling evasion of mercury from surface waters in the Everglades Nutrient Removal Project

During the period 1996-1998, and covering each of the four climatic seasons, we measured evasion of Hg using flux chambers over waters of the Everglades Nutrient Removal Project (ENR), a constructed wetlands. In situ water evasion fluxes of total gaseous mercury (primarily Hg0) measured at seven Everglades sites typically show low evasion rates (< 3 ng m(-2) h(-1)), which are smaller on average than those measured in northern systems. Evasion exhibits a strong diel cycle, with the highest values during midday, and evasion rates are correlated with dissolved gaseous mercury (DGM), solar radiation, wind speed, and water temperature. A thin film model was adapted and applied to estimate evasion fluxes for these Everglades waters based on our measurements of DGM. The results suggest that the typical thin film model underestimates evasion for the Everglades waters, at least on a short time scale.