Gaseous Mercury Fluxes in Peatland Ecosystems

Kristine Haynes1,2, Carl P J Mitchell1,2, Randy Kolka3, Evan S Kane4,5, Lynette Potvin6 and Erik Lilleskov6, (1)University of Toronto, Department of Geography, Toronto, ON, Canada, (2)University of Toronto Scarborough, Physical and Environmental Sciences, Toronto, ON, Canada, (3)USDA Forest Service, Northern Research Station, Grand Rapids, MN, United States, (4)Michigan Technological University, School of Forest Resources and Environmental Sciences, Houghton, MI, United States, (5)USDA Forest Service, Northern Research Station, Houghton, United States, (6)USDA Forest Service, Northern Research Station, Houghton, MI, United States

Contact First Author: Kristine Haynes; k.haynes@utoronto.ca

Abstract ID#: 35281

 

English Abstract:
Minimal research has been done to investigate gaseous mercury (Hg) fluxes in peatland ecosystems. These immense stores of carbon are vulnerable to climate-induced changes in hydrology which may impact the dynamic exchange of Hg between the atmosphere and peatlands. It is therefore important to understand the extent to which these ecosystems act as a sink or source of atmospheric Hg. The goal of this research is to characterize total gaseous Hg fluxes at the field scale in a southern-extent boreal bog and examine how climate-induced changes in hydrology and dominant plant communities may affect the direction and magnitude of Hg fluxes. These fluxes were monitored in an ombrotrophic bog in the Marcell Experimental Forest in north-central Minnesota in spring and late summer of the 2014 growing season. Fluxes were also measured in mid-summer in a subset of the PEATcosm experimental mesocosms, simulating the anticipated effects of climate change. These effects consisted of two water table treatments (higher and lower) and three vegetation treatments (sedge removal, ericoid removal, no removals). Gaseous Hg fluxes in the ombrotrophic bog exhibit considerable spatial and seasonal variability with mean daily Hg fluxes ranging from -158.8 to +199.1 ng m-2 d-1 during May 2014 while August 2014 fluxes ranged from -38.9 to +59.2 ng m-2 d-1. Greater deposition of Hg to the peat is observed under the simulated condition of a lowered water table and predominantly sedge vegetation with a mean daily flux of -73.7 ng m-2 d-1 as compared to the low water table – unmanipulated (control) plant community mesocosms with a mean daily emission of +54.6 ng m-2 d-1. Correlative relationships are being investigated between Hg fluxes and incoming solar radiation, aboveground leaf area as well as peat Hg concentrations. Hydrological and ecological feedbacks as a result of a changing climate may have important implications for the exchange of atmospheric Hg with peatland ecosystems.
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