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>Differences in organic surface microlayers from an artificially acidified and control lake, elucidated by XAD-8/XAD-4 tandem separation and solid 13C NMR spectroscopy
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Differences in organic surface microlayers from an artificially acidified and control lake, elucidated by XAD-8/XAD-4 tandem separation and solid 13C NMR spectroscopy
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机译：Differences in organic surface microlayers from an artificially acidified and control lake, elucidated by XAD-8/XAD-4 tandem separation and solid 13C NMR spectroscopy
Solid state 13{sup left}C NMR spectroscopy was used to quantify the distribution of C functional groups in surface microlayer dissolved organic matter (DOM, <0.45μm) from an artificially acidified and a control freshwater lake in western Norway.Organic substances were extracted from pooled surface microlayers and collected with hydrophilic Teflon coated drum, using XAD-8/XAD-4 tandem separation. DOM was recovered at 80-85. Presence of 15-20 carbohydrates in the humic and fulvic acid fractionsof the acid-treated microlayer indicated greater influence of soil humic substances on microlayer DOM, compared with the control. Humic and fulvic acids and hydrophobic neutrals were enriched (ratio surface microlayer, subsurface water greater than 1) inthe surface microlayers of both basins. Aromatic fractions were reduced in the microlayer from the treated basin compared to the control. The dissimilarities are primarily believed to result from hydrological and geomorphologic differences between thelake basins, secondarily from acid degradation of the aromatic DOM in the microlayers. Higher aliphatic C in the acid treated than in the control surface microlayer supported the degradation theory, as did the lowered aromaticity found for all fractionsin the treated microlayer. Major influences were decreased (from 46 to 36) fulvic acid fraction and lowered aromaticity of all DOM fractions in the treated surface microlayer. The combined use of XAD-resin separation and 13{sup left}C NMR spectroscopyfor quantification of DOM from different surface microlayers proved useful for the comparative purposes of this environmental impact study. Some caution has to be taken to the use of pooled samples, however, and the results need to be collectedsimultaneously with in situ measurements, such as on-line fourier transfer infra-red spectroscopy.
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