Seasonal Variations in Net Methyl Mercury Production and Total Mercury Removal in a Constructed Wetland

Ten parallel wetland mesocosms with four replicate experimental designs were utilized to assess seasonal variation in total mercury (THg) removal and net methyl mercury (MeHg). Experimental designs included 1) Hg contaminated water and sediments (MW-MS), 2) Hg contaminated water and clean sediments (MW-CS), 3) clean water and Hg contaminated sediments (CW-MS), and 4) clean water and sediments (CW-CS). No seasonal variation in THg removal was observed for any experimental design. The designs receiving Hg contaminated water were sinks for THg with average removal of 59±29%. In contrast, designs receiving clean water were least effective in THg removal (18±34%). Seasonal variation in MeHg production was observed for designs MW-MS and CW-MS, with values peaking in the late spring and summer, whereas, other designs did not show seasonal variation. Sulfate and temperature were most important parameters found to drive MeHg.