The structure of freshwater humic substances as revealed by 13C-NMR spectroscopy |
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Authors: | MA Wilson PF Barron AH Gillam |
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Institution: | 1. Lincoln College, Canterbury, New Zealand;2. CSIRO, Fuel Geoscience Unit, P.O. Box 136, North Ryde, Australia;3. Department of Oceanography. The University of Liverpool, P.O. Box 147, Liverpool L69 3BX, U.K. |
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Abstract: | Freshwater humic substances from Lake Celyn, Gwynedd, N. Wales have been investigated by 13C-NMR spectroscopy. Carboxyl, aromatic, o-alkyl and alkyl resonances can be recognised. Varying pulse delay from 0.43 s to 2.5 sec has little effect on the magnitude of the signal ascribed to aromatic carbon, but there is a small nuclear Overhauser effect (1.45 at a pulse delay of 0.8 sec).The results show-that 24% of the Lake Celyn humic acid carbon is carboxyl and 40% is aromatic. The high proportion of aromatic carbon suggests the Lake Celyn humic acid is largely formed from terrestrial humic substances from the surrounding peaty watershed. |
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