The fate of mercury at two small co-located headwater watersheds in interior Alaska
Abstract
Deposition and ultimate fate of mercury (Hg) in northern latitudes has recently become of heightened concern. This is due to several factors possibly working in concert; 1) including increased atmospheric deposition during the past 150 years, 2) export of disproportionately large loads of total Hg from the Yukon River basin compared to other large northern rivers, 3) the thawing permafrost as a potential significant source of Hg to the global pool, 4) significant sources and stores of carbon in northern soils and water; and 5) the role of atmospheric mercury depletion events (AMDE). A process-based study to better understand the mechanism by which Hg can move from the atmosphere through aquatic and terrestrial environments into the global pool has been initiated at two small paired headwater watersheds underlain by discontinuous permafrost in boreal interior Alaska. Headwater streams throughout interior Alaska, although small, typically make up half the length of northern interior stream networks potentially playing a considerable role in Hg cycling processes. We will present preliminary results from the first year of a study designed to assess the influence of carbon, permafrost, fire, and changing hydrologic conditions. Surface and soil water samples were collected at 10-12 day intervals throughout the open-water season at co-located West Twin and East Twin Creek watersheds (4 and 6 km2, respectively). These basins exhibit differences in recent forest burn areas and water discharge. During peak flow (spring snowmelt, 2012), instantaneous total Hg yields for both watersheds ranged from 1 to 4 ug/m2/yr (for comparison, yields from the Yukon River basin average 5 ug/m2/yr). Ratios of dissolved methylmercury to dissolved total mercury for both watersheds were 2-4% (common for first order streams at mid latitudes). Additional results and discussion of Hg exports and yields will focus on transport and methylation processes in the context of similar and contrasting watershed characteristics. Recent results from permafrost mapping, groundwater hydrology and soil methylation-demethylation potential studies will also be presented.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B31C0426S
- Keywords:
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- 0414 BIOGEOSCIENCES / Biogeochemical cycles;
- processes;
- and modeling;
- 0496 BIOGEOSCIENCES / Water quality;
- 0706 CRYOSPHERE / Active layer;
- 1879 HYDROLOGY / Watershed