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Quantification of natural DOM from UV absorption at two wavelengths

By Edward Tipping, Heather T. Corbishley, Jean-Francois Koprivnjak, Daniel J. Lapworth, Matthew P. Miller, Colin D. Vincent and John Hamilton-Taylor

Abstract

The precise simulation of ultraviolet absorption by 23 contrasting surface-water DOM samples was achieved with a model based on two components, one absorbing light strongly (A) and the other weakly (B). The parameterised model can be used to predict [DOC] in water samples simply from absorbance values at two wavelengths, while information on DOM quality is provided by the calculated fractionation into A and B. The model was tested by predicting [DOC] for a separate dataset obtained by combining results for 12 samples each from surface waters in the UK, Canada and the USA, and from UK groundwaters. A close correlation (R2 = 0.997) was obtained, with only slight underestimation of the true [DOC]. The proportions of components A and B varied considerably among the sites, which explains why precise prediction of [DOC] from absorbance data at a single wavelength was not possible. When the model was applied to samples collected from river locations in a heterogeneous UK catchment with areas of industry and high human population, [DOC] was underestimated in many cases, which may indicate the presence of non-absorbing pollutant DOM

Topics: Ecology and Environment, Chemistry
Publisher: CISRO Publishing
Year: 2009
DOI identifier: 10.1071/EN09090
OAI identifier: oai:nora.nerc.ac.uk:9071

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