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Article

Evaluation of Specific Ultraviolet Absorbance as an Indicator of the Chemical Composition and Reactivity of Dissolved Organic Carbon

James L. Weishaar,^† George R. Aiken,*^† Brian A. Bergamaschi,^‡ Miranda S. Fram,^‡ Roger Fujii,^‡ and Kenneth Mopper^§

U.S. Geological Survey, 3215 Marine Street, Boulder, Colorado 80303, and U.S. Geological Survey, 6000 J Street, Placer Hall, Sacramento, California 95819

Environ. Sci. Technol., 2003, 37 (20), pp 4702–4708

DOI: 10.1021/es030360x

Publication Date (Web): September 17, 2003

†

U.S. Geological Survey, Boulder, CO.

Corresponding author phone: (303)541-3036; fax: (303)447-2505; e-mail: graiken@usgs.gov.

‡

U.S. Geological Survey, Sacramento, CA.

Current Address: Old Dominion University, Chemistry Depart ment, Norfolk, VA 23529.

Abstract

Specific UV absorbance (SUVA) is defined as the UV absorbance of a water sample at a given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined at 254 nm, is strongly correlated with percent aromaticity as determined by ¹³C NMR for 13 organic matter isolates obtained from a variety of aquatic environments. SUVA, therefore, is shown to be a useful parameter for estimating the dissolved aromatic carbon content in aquatic systems. Experiments involving the reactivity of DOC with chlorine and tetra- methylammonium hydroxide (TMAH), however, show a wide range of reactivity for samples with similar SUVA values. These results indicate that, while SUVA measurements are good predictors of general chemical characteristics of DOC, they do not provide information about reactivity of DOC derived from different types of source materials. Sample pH, nitrate, and iron were found to influence SUVA measurements.

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