Evasion of Elemental Mercury from a Boreal Peatland Suppressed by Long-Term Sulfate Addition

We investigated the evasion of TGM (total gaseous mercury) fromexperimental plots on a boreal peatland that had been exposed for 15 years todifferent combinations of atmospheric sulfur (S) and nitrogen (N) deposition as wellas greenhouse treatments simulating climate change. Shaded dynamic flux chambermeasurements during the summer in 2009 showed emission of TGM to theatmosphere from most of the treated plots (0.7 ± 0.94 ng m−2 h−1). However, TGMexchange rates were significantly lower, occasionally indicating Hg uptake, on plotssubjected to S addition at rates of 20 kg ha−1 year−1. Enhanced nitrogen depositionand greenhouse treatment had no significant effect on TGM fluxes. We hypothesizethat the lower Hg evasion from the sulfur-treated plots is related to either earlier Hgevasion or Hg binding to S in organic matter, making Hg less susceptible tovolatilization and more prone to transport in runoff.