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The rate of loss of dissolved organic carbon (DOC) through a catchment

Moody, C.S.; Worrall, F.; Evans, C.D.; Jones, T.

The rate of loss of dissolved organic carbon (DOC) through a catchment Thumbnail


Authors

C.S. Moody

C.D. Evans

T. Jones



Abstract

Given observed trends in the concentration of DOC in surface waters in the northern hemisphere the degradation of DOC to CO2 could represent a major and increasing source of greenhouse gas to the atmosphere. However, studies of DOC turnover in rivers have been predominantly based upon mass balance studies and empirical studies have focused upon lakes and estuaries which have far longer residence times than would be the case for transit via rivers. The study measured DOC loss in unfiltered river water samples across an 818 km2 catchment every month for a year and considered total loss, photo and aphotic degradation as well as the rates of each process. The study found: (i) Rate of total DOC change in daylight varied from loss of 30.1 mg C/l/day to an increase of 3.5 mg C/l/day: the average loss was 73% over 10 days. (ii) Rate of change due to photic processes varied from decrease of 19.4 mg C/l/day to an increase of 6 mg C/l/day, i.e. net photo-induced production was possible. (iii) Activation energy of the degradation was estimated as 2.6 ± 1.2 kJ/g C. (iv) The apparent quantum yield varied from 9.6 to −1.7 mmol C/mol photons. (v) Coupling models of total loss of DOC with estimates of in-stream residence times showed that annual loss rates of DOC across the 818 km2 catchment would be between 48% and 69%, in line with estimates from mass balance studies, implying that in-stream DOC degradation represents a large, indirect source of CO2 emissions from peats and other organic soils. (vi) Annual rate of removal was increasing in line with increasing loss of DOC at source, implying that observed DOC trends are leading to increased CO2 emissions.

Citation

Moody, C., Worrall, F., Evans, C., & Jones, T. (2013). The rate of loss of dissolved organic carbon (DOC) through a catchment. Journal of Hydrology, 492, 139-150. https://doi.org/10.1016/j.jhydrol.2013.03.016

Journal Article Type Article
Publication Date Jun 7, 2013
Deposit Date May 14, 2014
Publicly Available Date Jun 9, 2014
Journal Journal of Hydrology
Print ISSN 0022-1694
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 492
Pages 139-150
DOI https://doi.org/10.1016/j.jhydrol.2013.03.016
Keywords DOC, Peat, Degradation, Greenhouse gases.

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Copyright Statement
NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Hydrology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Hydrology, 492, 2013, 10.1016/j.jhydrol.2013.03.016.







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