Seasonal variation in dissolved gaseous mercury and total mercury concentrations in Juam Reservoir, Korea

Dissolved gaseous mercury (DGM) and total mercury (TM) concentrations were measured in Juam Reservoir, Korea. DGM concentrations were higher in spring (64 ± 13 pg L−1) and summer (109 ± 15 pg L−1), and lower in fall (20 ± 2 pg L−1) and winter (23 ± 6 pg L−1). In contrast, TM concentrations were higher in fall (3.2 ± 0.1 ng L−1) and winter (3.3 ± 0.1 ng L−1) than in spring (2.3 ± 0.1 ng L−1) and summer (2.2 ± 0.4 ng L−1). DGM concentrations were correlated with water temperature (p < 0.0001), ORP (p < 0.0001), UV intensity (UV-A: p = 0.008; UV-B: p = 0.003), and DOC concentration (p = 0.0107). DGM concentrations varied diurnally with UV intensity. The average summer DGM (109 ± 15 pg L−1) and TM (2.2 ± 0.4 ng L−1) concentrations in Juam Reservoir were higher than the averages for North American lakes (DGM = 38 ± 16 pg L−1; TM = 1.0 ± 1.2 ng L−1), but lower than levels reported for Baihua Reservoir in China.