Much still remains unknown about biogeochemical cycle of Hg in reservoir lakes and artificial impoundments. We conducted a consecutive 12-month field study from June, 2003 to May, 2004 to follow the kinetics of dissolved gaseous mercury (DGM) in Cane Creek Lake, a southern reservoir lake in Cookeville of TN, to quantify the seasonal DGM photochemokinetics. Strong diurnal kinetic cycles of DGM loading in the lake closely tracing daily insolation march were found to prevail in the late spring and summer while vague diurnal DGM kinetics was common in the late autumn and winter. Low in January, the monthly mean DGM concentrations gradually rise, peak in July, and then consistently fall to the lowest in December. The rise of the DGM loading in the lake from January to July followed by its fall from July to December dramatically mirrors the two phases of the typical daily DGM kinetics (morning rise vs. afternoon fall). The seasonal trends were also found of high DGM loading in summer (mean: 37.5 pg/L) and spring (mean: 34.4 pg/L) and low DGM loading in fall (mean: 20.6 pg/L) and winter (mean: 24.4 pg/L). The kinetic changes of DGM in the lake intimately traced the insolation on both daily and seasonal scales. Good linear correlations of the monthly mean DGM concentrations were found with the monthly mean global solar radiation and the monthly mean UVA radiation. Apparently better correlations were found of the seasonal mean DGM concentrations with the seasonal mean global solar radiation and the seasonal mean UVA radiation.
*Current address: The University of The South at Suwannee
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