Mercury in freshwaters of the Yukon-Kuskokwim delta, Alaska
Abstract
Tundra regions store globally significant quantities of mercury (Hg) in active layer and permafrost soils, and are experiencing greater rates of atmospheric Hg deposition since industrialization. Freshwater environments act as critical intermediaries between upland soil organic Carbon loss and methylmercury uptake by freshwater organisms, which is a critical vector for biological exposure to humans. Despite this, little information is available on freshwater mercury concentrations and its spatial variability in Arctic environments. To address these knowledge gaps, we measured Hg concentrations in freshwaters across the Yukon-Kuskokwim delta, Alaska during July 2018. We collected 58 waters from lakes spanning 12 m2 to 0.36 km2 in surface area across the landscape. We found a significant negative linear relationship between water body size and dissolved organic carbon concentrations, demonstrating a greater transfer of Carbon (C) between terrestrial stocks and smaller water bodies. Using pre-existing C to Hg relationships (1), we initially estimate average Hg concentrations to vary between 3.5 - 5.8 ng Hg L-1 within lakes and total Hg freshwater stocks to range from 1.6 to 9.7 Tg Hg over our 274 km2 study area. We also present direct Hg measurements from waters and examine dissolved C:Hg ratios across the delta to investigate how differences in lake environmental conditions (e.g. pH, oxygen availability) may alter the relative amount of Hg in C stocks. These results highlight the importance of incorporating freshwaters stocks of Hg into our understanding of Arctic ecosystems and provide crucial information on the potential mobilization of terrestrial Hg stocks to the aquatic environment with important ramifications for human health.
(1) Driscoll, C.T. et al., 1995. The role of dissolved organic carbon in the chemistry and bioavailability of mercury in remote Adirondack lakes. Water, Air, and Soil Pollution, 80(1-4), pp.499-508.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B31F2553T
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 1640 Remote sensing;
- GLOBAL CHANGE