title: Production and retention of methylmercury in inundated boreal forest soils.
abstract: The Flooded Uplands Dynamics Experiment (FLUDEX) was an ecosystem-scale study examining the production of methylmercury (MeHg) and greenhouse gases from reservoirs constructed on an upland boreal forest landscape in order to quantify their dependence upon carbon stores. We detail the within-reservoir production and storage of MeHg before, during, and nine years after the experiment. The reservoirs were net MeHg producers during the first two years of flooding, and net demethylating systems afterward. During years 1-3, a rapid pulse of MeHg and total Hg was observed in floodwater, followed by substantial increases in MeHg in seston and sediment. Resampling of the dry reservoirs nine years after the experiment ended indicated that organic soil MeHg was still 8 to 52-fold higher than preflood conditions, and averaged 86% of the levels recorded at the end of the third flooding year. Both total Hg and MeHg retention in soil were a strong function of organic carbon content. The time scale of soil MeHg retention may help explain the decadal time lag frequently observed for the decrease of piscivorous fish Hg concentrations in new reservoirs. Predicted extreme precipitation events associated with climate change may serve to make landscapes more susceptible to this process.
authors: †Department of Chemistry and Biochemistry, River Studies Center, University of Wisconsin-La Crosse, La Crosse, Wisconsin 54601, United States.
authors: Kristofer R
authors: KR
authors: Rolfhus
authors: ‡Department of Civil and Environmental Engineering, Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
authors: James P
authors: JP
authors: Hurley
authors: §Penobscot River Mercury Study, 115 Oystercatcher Place, Salt Spring Island, British Columbia, Canada V8K 2W5.
authors: Richard A Drew
authors: RA
authors: Bodaly
authors: †Department of Chemistry and Biochemistry, River Studies Center, University of Wisconsin-La Crosse, La Crosse, Wisconsin 54601, United States.
authors: Gregory
authors: G
authors: Perrine
mesh_terms: D017752:Greenhouse Effect; D060106:Lakes; D008767:Methylmercury Compounds / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D066188:Taiga; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D012987:Soil; D014874:Water Pollutants, Chemical