Abstract
JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
G04S51,
14 PP., 2007
doi:10.1029/2006JG000343
Chemical characteristics of fulvic acids from Arctic surface waters: Microbial contributions and photochemical transformations
Institute of Arctic and Alpine Research and Civil and Environmental Engineering, University of Colorado, Boulder, Colorado, USA
Institute of Arctic and Alpine Research and Civil and Environmental Engineering, University of Colorado, Boulder, Colorado, USA
Geological Sciences, Ohio State University, Columbus, Ohio, USA
Department of Chemistry, Rose-Hulman Institute of Technology, Terre Haute, Indiana, USA
Institute of Arctic and Alpine Research and Civil and Environmental Engineering, University of Colorado, Boulder, Colorado, USA
Dissolved organic matter (DOM) originating from the extensive Arctic tundra is an important source of organic material to the Arctic Ocean. Chemical characteristics of whole water dissolved organic matter (DOM) and the fulvic acid fraction of DOM were studied from nine surface waters in the Arctic region of Alaska to gain insight into the extent of microbial and photochemical transformation of this DOM. All the fulvic acids had a strong terrestrial/higher plant signature, with uniformly depleted δ 13C values of −28‰, and low fluorescence indices around 1.3. Several of the measured chemical characteristics of the Arctic fulvic acids were related to water residence time, a measure of environmental exposure to sunlight and microbial activity. For example, fulvic acids from Arctic streams had higher aromatic contents, higher specific absorbance values, lower nitrogen content, lower amino acid–like fluorescence and were more depleted in δ 15N relative to fulvic acids isolated from lake and coastal surface waters. The differences in the nitrogen signature between the lake and coastal fulvic acids compared to the stream fulvic acids indicated that microbial contributions to the fulvic acid pool increased with increasing water residence time. The photo-lability of the fulvic acids was positively correlated with water residence time, suggesting that the fulvic acids isolated from source waters with larger water residence times (i.e., lakes and coastal waters) have experienced greater photochemical degradation than the stream fulvic acids. In addition, many of the initial differences in fulvic acid chemical characteristics across the gradient of water residence times were consistent with changes observed in fulvic acid photolysis experiments. Taken together, results from this study suggest that photochemical processes predominantly control the chemical character of fulvic acids in Arctic surface waters. Our findings show that hydrologic transport in addition to biogeochemical alteration of the organic matter must be considered in order to predict the ultimate fate of Arctic DOM.
Received 11 October 2006; accepted 30 May 2007; published 7 December 2007.
Citation: (2007), Chemical characteristics of fulvic acids from Arctic surface waters: Microbial contributions and photochemical transformations, J. Geophys. Res., 112, G04S51, doi:10.1029/2006JG000343.
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