title: Methylmercury declines in a boreal peatland when experimental sulfate deposition decreases.
abstract: Between 2001 and 2008 we experimentally manipulated atmospheric sulfate-loading to a small boreal peatland and monitored the resulting short and long-term changes in methylmercury (MeHg) production. MeHg concentrations and %MeHg (fraction of total-Hg (Hg(T)) present as MeHg) in the porewaters of the experimental treatment reached peak values within a week of sulfate addition and then declined as the added sulfate disappeared. MeHg increased cumulatively over time in the solid-phase peat, which acted as a sink for newly produced MeHg. In 2006 a "recovery" treatment was created by discontinuing sulfate addition to a portion of the experimentally treated section to assess how MeHg production might respond to decreased sulfate loads. Four years after sulfate additions ceased, MeHg concentrations and %MeHg had declined significantly from 2006 values in porewaters and peat, but remained elevated relative to control levels. Mosquito larvae collected from each treatment at the end of the experiment exhibited Hg(T) concentrations reflective of MeHg levels in the peat and porewaters where they were collected. The proportional responses of invertebrate Hg(T) to sulfate deposition rates demonstrate that further controls on sulfur emissions may represent an additional means of mitigating Hg contamination in fish and wildlife across low-sulfur landscapes.
authors.affiliation: Water Resources Science Graduate Program, University of Minnesota, 173 McNeal Hall, 1985 Buford Avenue, St Paul, Minnesota 55108, United States. colemajk@umn.edu
authors.forename: Jill K
authors.initials: JK
authors.lastname: Coleman Wasik
authors.forename: Carl P J
authors.initials: CP
authors.lastname: Mitchell
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Engstrom
authors.forename: Edward B
authors.initials: EB
authors.lastname: Swain
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Monson
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Balogh
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Jeremiason
authors.forename: Brian A
authors.initials: BA
authors.lastname: Branfireun
authors.forename: Susan L
authors.initials: SL
authors.lastname: Eggert
authors.forename: Randall K
authors.initials: RK
authors.lastname: Kolka
authors.forename: James E
authors.initials: JE
authors.lastname: Almendinger
mesh_terms: D008767:Methylmercury Compounds / Q000032:analysis*; D013447:Sulfites / Q000032:analysis*; D053833:Wetlands
chemical_list: D008767:Methylmercury Compounds; D013447:Sulfites