Characterization and origin of dissolved organic carbon in Yegua ground water in Brazos County, Texas

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From: Ground Water(Vol. 39, Issue 5)
Publisher: National Ground Water Association
Document Type: Article
Length: 5,528 words

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Abstract :

Dissolved organic carbon (DOC) concentrations in five shallow ( 3000 amu, IMW 1000 to 3000 amu, and LMW 500 to 1000 amu) and combined neutral sugar analyses provide information on organic matter sources in the Yegua aquifers. Combined neutral sugars ranged in concentration from 0.6 to 2.7 [micro]mol/L and comprised 0.8% to 6.7% of DOC in ground water. Glucose was the most abundant neutral sugar, followed by xylose and galactose, arabinose, mannose, rhamnose, and fucose. These combined neutral sugars were more diagenetically altered in shallow, oxic ground water as indicated by high mole % fucose + rhamnose and low neutral sugar yield. The precursors for neutral sugars are most probably angiosperm leaves, which show a similar distribution pattern of neutral sugars. Ground water DOC was depleted in [C.sup.13] relative to soil-zone organic matter (OM) (-16[percent thousand] to -19[percent thousand]). The [delta][C.sup.13] values of bulk DOC and HMW DOC ranged from -24[percent thousand] to -32[percent thousand], whereas LMW and IMW DOC ranged from -32[percent thousand] to -34[percent thousand] and -16[percent thousand] to -28[percent thousand], respectively. This variability in [delta][C.sup.13] values is probably related to microbial processes and selective preservation of OM. Carbon isotope analyses in bulk and different molecular weight DOC fractions imply a predominantly [C.sub.3] OM source and a low contribution of soil-zone OM to DOC.

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Gale Document Number: GALE|A84601012