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Abstract Dissolved organic matter (DOM) concentrations and composition within wet deposition are rarely monitored despite contributing a large input of bioavailable dissolved organic carbon (DOC) and nitrogen (DON) to the Earth's surface. Lacking from the literature are spatially comprehensive assessments of simultaneous measurements of wet deposition DOC and DON chemistry and their dependencies on metrics of climate and environmental factors. Here, we use archived precipitation samples from the US National Atmospheric Deposition Program collected in 2017 to 2018 from 17 sites across six ecoregions to investigate variability in the concentration and composition of depositional DOM. We hypothesize metrics of DOM chemistry vary with ecoregion, season, large‐scale climate drivers, and precipitation geographic source. Findings indicate differences in DOC and DON concentrations and loads among ecoregions. The highest wet deposition concentrations are from sites in the Northern Forests and lowest concentrations from sites in Marine West Coast Forests. Summer and autumn samples contained the highest DOC concentrations and DON concentrations that were consistently above detection limit, corresponding with seasonality of peak air temperatures and the phenology of the growing season in the northern hemisphere. Compositional trends suggest lighter DOM molecules in autumn and winter and heavier molecules in spring and summer. Climate drivers explain 51% of variation in DOM chemistry, revealing differing drivers on the concentrations and loads of DOC versus DON in wet deposition. This study highlights the necessity of incorporating DOC and DON measurements into national deposition monitoring networks to understand spatial and temporal feedbacks between climate change, atmospheric chemistry and landscape biogeochemistry.
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Ecohydrology of two northern Wisconsin bogs
Abstract The dynamics of water and solutes were investigated in two northern bog ponds using sensor networks and discrete water samples. Embedded sensors monitored water level (S), precipitation (P), evaporation (E), water temperature (T) and specific conductivity (SC) in the peatlands and encircled ponds at 30 min time intervals from 2009 to 2015. Pond water chemistry was monitored seasonally from 2000 to 2020. Daily hydrographs and water budgets indicated that both bogs are ombrotrophic systems, perched above the local water table. Although the predominant flowpath for liquid water was precipitation → pond → peatland → underlying glacial deposits, evaporation accounted for 70% to 90% of water losses. High dissolved organic matter (DOM) in the ponds resulted from transient reversals of flowpath and from molecular diffusion across the peatland/pond interface (a tea bag effect). DOM of peatland origin dominated pond water chemistry, regulating the concentration of important metals, major nutrients and the acid–base status of both bog ponds. Elevated concentrations of Fe, Hg and MeHg in the ponds reflected ligand binding by DOM. The formation of DOM‐Fe‐PO4complexes likely accounted for >3‐fold higher P concentration relative to nearby clearwater lakes. Linear regression of dissolved organic carbon (DOC) against the anion deficit indicated that DOM contributed up to 6.6 mEq of strong acid per gramme carbon in pond waters. Winter maxima in the seasonal cycles of DOC, Ca, Mg, N, P, Hg and MeHg in both bog ponds were attributable, in large part, to salting out during ice formation. We conclude that multiple methods are needed to understand the dynamics of water and solutes in bog ecosystems.
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- Award ID(s):
- 2025982
- PAR ID:
- 10480758
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecohydrology
- Volume:
- 16
- Issue:
- 8
- ISSN:
- 1936-0584
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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