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|title: ||Comparative characterization of humic substances from the open ocean, estuarine water and fresh water|
|authors: ||Esteves, Valdemar I.|
Duarte, Armando C.
|issue date: ||2009|
|abstract: ||Humic substances were isolated from ocean, estuarine water and fresh water using a two column array of
XAD-8 and XAD-4 resins in series. The extracted fulvic acids and XAD-4 fraction from different origins
were characterized using UV–vis., molecular fluorescence, Fourier transform infrared (FTIR) spectroscopy
and cross polarization magic angle spinning (CPMAS)-13C nuclear magnetic resonance (NMR) spectroscopy.
The isolation procedure allowed us to obtain the necessary amount of sample for characterization,
even in the case of open ocean water, which has a very low amount of dissolved organic carbon (DOC).
Humic substances from the open ocean showed the lowest chromophore and fluorophore contents and
showed relatively greater fluorescence at lower wavelengths than those from fresh water. FTIR and 13C
NMR spectra highlighted the idea that humic substances from a marine environment have a more
branched aliphatic structure and less aromatic structure than those highly influenced by terrestrial
sources. The spectra also suggest that the open ocean humic substances have a higher content of olefinic
carbons than aromatic- or alkyl-substituted carbons.|
|publisher version/DOI: ||http://dx.doi.org/10.1016/j.orggeochem.2009.06.006|
|source: ||Organic Geochemistry|
|appears in collections||DQ - Artigos|
PT Mar - Artigos
Ria - Artigos
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