Elucidating effects of atmospheric deposition and peat decomposition processes on mercury accumulation rates in a northern Minnesota peatland over last 10,000 cal years

Edward A Nater, University of Minnesota - Twin Cities, Saint Paul, MN, United States, Olha Furman, Australian Government, Department of Agriculture, Water, and the Environment, Canberra, Australia, Brandy M Toner, University of Minnesota Twin Cities, Department of Soil, Water, and Climate, St. Paul, United States, Stephen D Sebestyen, USDA Forest Service Northern Research Station, Grand Rapids, United States, Malak M Tfaily, University of Arizona, Department of Environmental Sciences, Tucson, AZ, United States, Jeff Chanton, Florida State University, Department of Earth, Ocean & Atmospheric Science, Tallahassee, United States, Cinzia Fissore, Whittier College, Whittier, CA, United States, Karis J McFarlane, Lawrence Livermore National Laboratory, Livermore, CA, United States, Paul J Hanson, Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, United States, Colleen M. Iversen, Oak Ridge National Laboratory, Climate Change Science Institute and Environmental Sciences Division, Oak Ridge, United States and Randy Kolka, USDA Forest Service, Vallejo, CA, United States
Abstract:
Climate change has the potential to affect mercury (Hg), sulfur (S) and carbon (C) stores and cycling in northern peatland ecosystems (NPEs). SPRUCE (Spruce and Peatland Responses Under Climate and Environmental change) is an interdisciplinary study of the effects of elevated temperature and CO2 enrichment on NPEs. Peat cores (0-3.0 m) were collected from 16 large plots located on the S1 peatland (an ombrotrophic bog treed with Picea mariana and Larix laricina) in August, 2012 for baseline characterization before the experiment begins. Peat samples were analyzed at depth increments for total Hg, bulk density, humification indices, and elemental composition. Net Hg accumulation rates over the last 10,000 years were derived from Hg concentrations and peat accumulation rates based on peat depth chronology established using 14C and 13C dating of peat cores. Historic Hg deposition rates are being modeled from pre-industrial deposition rates in S1 scaled by regional lake sediment records. Effects of peatland processes and factors (hydrology, decomposition, redox chemistry, vegetative changes, microtopography) on the biogeochemistry of Hg, S, and other elements are being assessed by comparing observed elemental depth profiles with accumulation profiles predicted solely from atmospheric deposition. We are using principal component analyses and cluster analyses to elucidate relationships between humification indices, peat physical properties, and inorganic and organic geochemistry data to interpret the main processes controlling net Hg accumulation and elemental concentrations in surface and subsurface peat layers. These findings are critical to predicting how climate change will affect future accumulation of Hg as well as existing Hg stores in NPE, and for providing reference baselines for SPRUCE future investigations.
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