Sunlight-induced formation of dissolved gaseous mercury in lake waters

Formation of dissolved gaseous mercury (DGM) was measured in lake water incubated at midday in Teflon bottles. DGM production was photoinduced as transparent bottles yielded DGM concentrations that were 2.4-9 times higher than dark controls. These results provide the first experimental evidence obtained in the field of a direct link between solar radiation and DGM production. A positive relationship was found between photoinduced DGM production at different times of the year and incident radiation. Removal of UV B light or addition of hydrogen peroxide during incubation did not result in significant changes in DGM levels. A diel pattern in DGM production was observed, and a depth profile of DGM revealed that most of the production was occuring in the epilimnion