A Paleoenvironmental Record of Atmospheric Mercury Deposition in a Permafrost Core from Northern Alaska
Abstract
An estimated 13 percent of the earth's land surface is covered by permafrost. Northern regions are experiencing permafrost degradation due to climate change which may have major implications for the cycling of carbon, nutrients, and metals, particularly mercury (Hg) in arctic and subarctic ecosystems. An organic- rich core of perennially frozen soil 50 cm below the soil surface (7 cm in diameter and 72 cm in length) was collected from a forested peatland region of continuous permafrost near Coldfoot, Alaska, in August, 2005 (latitude about 67 degrees). The core was processed using trace metal clean sampling protocols. Forty-five samples cut at 1.6 cm intervals, were sent to the USGS Mercury Lab in Middleton, Wisconsin, for analysis of total Hg using low-level analytical methods. The use of permafrost soil cores for the examination of Hg accumulation histories is not apparent from the open literature. Results from this core reveal a range of Hg concentration from 70 to 250 ng/g. Mercury concentrations are elevated by about 50 percent compared to the mean for the entire core at a depth range of 70 to 95 cm from the surface, suggesting a prolonged event of elevated atmospheric Hg deposition. A Carbon-14 date at 55 cm below surface was 7500 years BP. This preliminary data suggests that: (1) As global warming continues, melting permafrost soils containing a large reservoir with the potential to add to the global Hg cycling pool are a possible future hot spot source of Hg, and: (2) there appear to be pre-industrial periods on the scale of millennia ("hot episodes") when atmospheric deposition of Hg was elevated. Additional radiocarbon dates will be presented along with results from another frozen soil core collected in discontinuous permafrost at a latitude of about 65 degrees.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.B13C0452S
- Keywords:
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- 0461 Metals;
- 0475 Permafrost;
- cryosphere;
- and high-latitude processes (0702;
- 0716);
- 1621 Cryospheric change (0776)