Vertical Stratification of Peat Pore Water Dissolved Organic Matter composition in a peat bog in Northern Minnesota
Authors/Creators
- 1. Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354
- 2. Department of Earth Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306
- 3. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, USA
- 4. School of Biology and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
- 5. Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
Description
Currently peatlands represent a sink for carbon dioxide and source of atmospheric methane. It is unclear the impact that climate change will have on these systems. As such, a large-scale ecosystem manipulation (Spruce and Peatland Responses under Climatic and Environmental Change, SPRUCE) has been implemented at a peat bog (S1 bog) at the Marcel Experimental Forest (MEF), Minnesota, USA, to determine the effects of climatic forcing on ecosystem processes in northern peatlands. In this study, we aimed to: (i) identify peat pore water dissolved organic matter (DOM) composition as a function of depth before the initiation of the manipulation experiment and (ii) contribute to the knowledge of DOM chemistry and decomposition processes at the S1 bog. We found strong vertical resolution in DOM molecular composition and optical properties within the peat column at the S1 bog. Surface samples were dominated by inputs from surface vegetation. The mid-depth, 30-75cm was an area of high reactivity and increased microbial activity with diagenetic formation of many unique compounds such as polycyclic aromatic compounds (PAC) that contain both nitrogen and sulfur heteroatoms. These compounds were previously observed in coal-derived products and were assumed to be responsible for coal’s biological activity. Biological processes taking place at the intermediate depth zone of the peat profile at the S1 bog are assumed to be responsible for the formation of these heteroatomic PAC in our system. Conversely, these compounds might stem from black carbon and nitrogen from potential fires that occurred at the site in the past. Surface and deep DOM exhibited more similar characteristics suggesting the possibility of lateral and vertical advection of pore water from the surface to the deeper horizons. Our results highlight the importance of understanding processes that control DOM production and transformation with depth.
Included: FTICR MS data and optical properties data