Marine organic matter spectroscopy

In contrast to infrared spectrometry there is no decrease in relative sensitivity in the lower energy region of the spectrum, and since no solvent is required, no part of the spectrum contains solvent absorptions. Oil samples contaminated with sand, sediment, and other solid substances have been analysed directly, after being placed between 0.5 mm 23-reflection crystals. Crude oils, which were relatively uncontaminated and needed less sensitivity, were smeared on a 2 mm 5-reflection crystal. The technique has been used to differentiate between crude oils from natural marine seepage, and accidental leaks from a drilling platform. The technique overcomes some of the faults of infrared spectroscopy, but is still affected by weathering and contamination of samples by other organic matter. The absorption bands shown in Table 9.1 are important in petroleum product identification. 

Tremblay, L. B., Dittmar,T., Marshall, A. G., Cooper, W. J., and Cooper, W.T. (2007). Molecular characterization of dissolved organic matter in a North Brazilian mangrove porewater and mangrove-fringed estuaries by ultrahigh resolution Fourier transform-ion cyclotron resonance mass spectrometry and excitation/emission spectroscopy. Marine Chem. 105, 15-29. 

Mopper, K., Stubbins, A., Ritchie, J. D., Bialk, H. M., and Hatcher, P G. (2007). Advanced instrumental approaches for characterization of marine dissolved organic matter Extraction techniques, mass spectrometry, and nuclear magnetic resonance spectroscopy. Chem. Rev. 107,419-442. 

Brandes, J. A., Lee, C., Wakeham, S., Peterson, M., Jacobsen, C., Wirick,S., and Cody, G. (2004). Examining marine particulate organic matter at sub-micron scales using scanning transmission X-ray microscopy and carbon X-ray absorption near edge structure spectroscopy. Marine Chem. 92,107-121. 

A variety of spectroscopic techniques have been applied to DOC isolated from seawater by cross-flow ultrafiltration or adsorption onto XAD resins. The two techniques isolate very different organic fractions from seawater. Hydrophobic fractions (such as marine humic material) are isolated on XAD resins [48], whereas the organic matter extracted by ultrafiltration is retained primarily on the basis of its molecular size and shape [49], resulting in isolates rich in nitrogen and carbohydrates (polysaccharides). Nuclear magnetic resonance (NMR) spectroscopy has proven successful in distinguishing between the specific structures of XAD-bound humics and the carbohydrates concentrated into colloidal size fractions. 

Murphy, K.R., Stedmon, C.A., Waite, T.D., and Ruiz, G.M. (2008). Distinguishing between terrestrial and autochthonous organic matter sources in marine environments using fluorescence spectroscopy. Mar. Chem., 108,40-58. 

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