Abstract
Biogeochemical processes in northern peatland ecosystems are influenced by seasonal temperature fluctuations that are changing with the climate. Methylmercury (MeHg), commonly produced in peatlands, affects downstream waters; therefore, it is important to understand how temperature transitions affect mercury (Hg) dynamics. We investigated how the freeze–thaw cycle influences belowground peat pore water total Hg (THg), MeHg, and dissolved organic carbon (DOC). Four large, intact peat columns were removed from an ombrotrophic peat bog and experimentally frozen and thawed. Pore water was sampled across seven depths in the peat columns during the freeze–thaw cycle and analyzed for THg, MeHg, and DOC concentrations. Freezing results showed increased concentrations of THg below the ice layers and limited change in MeHg concentrations. During thawing, THg concentrations significantly increased, whereas MeHg concentrations decreased. Limited bromide movement and depth decreases in THg and DOC concentrations were associated with increased bulk density and degree of humification in the peat. The experiment demonstrates the effects of the freeze–thaw cycle on Hg concentrations in northern peatlands. Changes to freeze–thaw cycles with climate change may exacerbate Hg cycling and transport processes in peatland environments.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 404-416 |
| Number of pages | 13 |
| Journal | Journal of Environmental Quality |
| Volume | 49 |
| Issue number | 2 |
| DOIs | |
| State | Published - Mar 1 2020 |
Bibliographical note
Funding Information:The Northern Research Station (NRS) of the USDA Forest Service funds the long-term monitoring and research program at the Marcell Experimental Forest. The NRS also funded this research as well as the contributions of RKK and SDS, and the Grand Rapids Forestry Sciences Chemistry Laboratory. Funding for the senior author was provided by the Graduate School and the College of Food, Agricultural, and Natural Resource Sciences, University of Minnesota. We thank Sona Psarska, Kalei Holt, and John Larson for water sample analysis and Matt Erickson, Andrew Scobbie, and John Baker for equipment, advice, and the use of their research space.
Funding Information:
The Northern Research Station (NRS) of the USDA Forest Service funds the long‐term monitoring and research program at the Marcell Experimental Forest. The NRS also funded this research as well as the contributions of RKK and SDS, and the Grand Rapids Forestry Sciences Chemistry Laboratory. Funding for the senior author was provided by the Graduate School and the College of Food, Agricultural, and Natural Resource Sciences, University of Minnesota. We thank Sona Psarska, Kalei Holt, and John Larson for water sample analysis and Matt Erickson, Andrew Scobbie, and John Baker for equipment, advice, and the use of their research space.
Publisher Copyright:
© 2020 The Authors. Journal of Environmental Quality © 2020 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America