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PII S0016-7037(01)00830-4 Chemical characterization of high molecular weight dissolved organic matter in fresh and
 

Summary: PII S0016-7037(01)00830-4
Chemical characterization of high molecular weight dissolved organic matter in fresh and
marine waters
DANIEL J. REPETA* TRACY M. QUAN, LIHINI I. ALUWIHARE and AMYMARIE ACCARDI
Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
(Received February 07, 2001; accepted in revised form May 30, 2001)
Abstract--The high molecular weight fraction of dissolved organic matter in a suite of lakes, rivers, seawater,
and marine sediment interstitial water samples was collected by ultrafiltration and characterized by molecular
level and spectroscopic techniques. Proton nuclear magnetic resonance spectra of all samples show a high
degree of similarity, with major contributions from carbohydrates, bound acetate, and lipids. Molecular level
analyses of neutral sugars show seven monosaccharides, rhamnose, fucose, arabinose, xylose, mannose,
glucose, and galactose, to be abundant, and to occur in comparable relative amounts in each sample. Previous
studies have emphasized the distinctive composition of dissolved humic substances in fresh and marine
waters, and have attributed these differences to sources and transformations of organic matter unique to each
environment. In contrast we find a large fraction of freshwater high molecular weight dissolved organic matter
(HMWDOM; 1kD) to be indistinguishable from marine HMWDOM in bulk and molecular-level chemical
properties. Aquatic HMWDOM is similar in chemical composition to biologically derived acylated hetero-
polysaccharides isolated from marine algal cultures, suggesting a biological source for some fraction of
persistent HMWDOM. High molecular weight DOC contributes 51 26% of the total DOC, and monosac-
charides 18 8% of the total HMWDOC in our freshwater samples. These contributions are on average

  

Source: Aluwihare, Lihini - Geosciences Research Division, Scripps Institution of Oceanography

 

Collections: Geosciences