1H and 13C NMR of marine humic acids

Chemical and biological studies on environmental humic acids II.1H-nmr and IR spectra of humic acids

“…It is likely that these protons arose from methoxyl groups and partly from OCH 2 -or OCH= groups, or carbohydrates (HATCHER et aL 1980). The peak in the 2.8 to 4.0 ppm region was attributed to methoxyl and carbohydrate protons.…”

“…Spectroscopic methods such as infrared, electron spin resonance, and nuclear magnetic resonance (NMR) have enabled to elucidate various structural characteristics of humic acids, and NMR has recently brought about considerable progress in the 384 K. YONEBA Y ASH I and T. HATTORI study of humic acids (HATCHER et al 1980). The NMR spectra of humic acids from terrestrial and aquatic origin indicated the presence of aromatic structures, most likely derived from lignin of vascular plants, as well as paraffinic structures, most likely derived from microbial sources (HATCHER et al 1981).…”

Organic Marine Geochemistry

“…Louda and E. W. Humic Substances Compared to the well defined structures and interrelationships of the discrete molecular biomarkers and geochemical indicators discussed above, relatively little is known about marine humic substances. Whether the major source of input to dissolved and sedimentary marine humic substances is of terrigenous or marine origin is s t i l l occasionally debated in the literature, although most interpretations point towards marine planktonic sources^ (12-^), based most convincingly on isotopic ratios, GC-MS, H and C NMR and infrared sy^ctra (15)(16)(17) source input indicator of terrestrial versus marine derived humic substances.…”

“…The important question of the reliability of quantification of solid state C NMR results can be answered in part by relaxation studies and the measurement of relaxation constants (25)(26)(27) C NMR has demonstrated that these substances have low aromaticities relative to terrestrial counterparts (16,28). The low aromatic (high aliphatic) content of marine humic substances is a result of their in situ production.…”

“…The early applications of C NMR to humic substances were done by solution NMR and were thus limited to base soluble humic and fuly^c acids (16,18,19). The subsequent application of solid-state C NMR to humic samples has allowed for direct comparisons between soluble and insoluble fractions as^ell as between humic substances from diverse environments.…”