Detailed Carbon Isotopic Characterization of Aerosol-Derived Organic Carbon Deposited to two Temperate Watersheds
Abstract
Atmospheric deposition of carbonaceous aerosols can be a quantitatively significant flux in the carbon budgets of temperate watersheds. Characterizing the sources and fates of this material is therefore critical for assessing its role in carbon and organic matter cycling in these systems. Aerosol samples were collected in the Hudson and York River watersheds throughout 2006-2007 and analyzed for quantities and isotopic signatures (δ13C, Δ14C) of total and water-soluble organic carbon (TOC, WSOC, respectively). On average ~2.4 and 2.1 mg m-2 d-1 of aerosol TOC were deposited to the Hudson and York River watersheds, respectively, and nearly half of this material was water-soluble. δ13C analyses indicated that both the TOC and the WSOC were primarily terrestrial in nature. TOC Δ14C signatures covered a broad range for both watersheds, with calculated contributions from fossil sources (e.g., anthropogenic combustion of petroleum, coal, etc.) ranging from 0% for samples collected during the summer of 2007 to approximately 50% for samples collected in the winter of 2007. Aerosol-derived WSOC Δ14C values were less variable and were nearly always enriched in 14C with respect to the corresponding TOC, indicating that contemporary aerosol material tends to partition into the aqueous phase, while fossil-derived aerosol OC is more likely to remain insoluble. However, WSOC still often showed considerable contributions from fossil OC (up to 20%). Thus, some portion of the anthropogenic fossil-derived aerosol OC is relatively soluble and may be transported hydrologically through watersheds and aquatic systems. A subset of aerosol samples from each watershed was selected for more thorough isotopic analysis of operationally-defined components of the carbonaceous material. Isotopic signatures were obtained for TOC, WSOC, total solvent-extract, and the aliphatic, aromatic, and polar components. Isotopic information on these fractions allows us to determine which components contribute to the age and source characteristics of aerosols. This information will help refine our understanding of the role of aerosol OC, and specifically, anthropogenically-derived aerosol OC, at the atmosphere-land-water interfaces.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.A21H..05W
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801;
- 4906);
- 0365 Troposphere: composition and chemistry;
- 0428 Carbon cycling (4806);
- 0454 Isotopic composition and chemistry (1041;
- 4870)