Effect of acidification of mercury methylation and volatilization in an oligotrophic Northern Wisconsin lake

The effects of experimental acidification on mercury methylation and volatilization were measured in sediment, water, and attached microbial communities (on artificial substrates) from an acid-susceptible Wisconsin lake. This research was initiated to determine potential mechanisms causing elevated mercury concentrations in biota of low pH waters. Methylation and volatilization rates were quantified by incubating samples with 203Hg(NO3) and measuring the formation of CH3 203HGplus and volatile 203Hg species, respectively. The effects of acidification on these processes were assessed by experimental acidification of samples with either HCl or H2S04. Methylation was greatest in surficial sediments (0-10 cm) from the profundal zone of the lake, and significantly less (p<0.01) in littoral and deeper sediments. The amounts of methylmercury produced in water and artificial substrate samples were very small, near the detection limit. Methylation in surficial sediments was significantly (p