Sediment molecular geochemical

Hinrichs K.-U., Summons R. E., Orphan V., Sylva S. P., and Hayes J. M. (2000) Molecular and isotopic analysis of anaerobic methan-oxidizing communities in marine sediments. Org. Geochem. 31, 1685-1701. 

Huang Y., Freeman K. H., Wilkin R. T., Arthur M. A., and Jones A. D. (2000) Black Sea chemocline oscillations during the Holocene molecular and isotopic studies of marginal sediments. Org. Geochem. 31, 1525-1531. 

Bian L., Hinrichs K.-U., Xie T., Brassell S. C., Iversen N., Fossing H., Jorgensen B. B., and Hayes J. M. (2001) Algal and archaeal polyisoprenoids in a recent marine sediment molecular isotopic evidence for anaerobic oxidation of methane. Geochem. Geophys. Geosys. 2 paper number 2000GC000112. 

Brincat, D., K. Yamada, R. Ishiwatari, H. Uemura H. Naraoka, 2000. Molecular-isotopic stratigraphy of long-chain n-alkanes in L.ake Baikal Holocene and glacial age sediments. Org. Geochem. 31 287-294. 

Huang YS, Lockheart MJ, Logan GA, Eglinton G, Isotope and molecular evidence for the diverse origins of carboxylic acids in leaf fossils and sediments from the Miocene Lake Glarkia deposit, Idaho, U.S.A, Org Geochem 24 289—299, 1996. 

The importance of these depositional environments makes it desirable that studies concerned with the reconstruction of palaeoenvironments from sediments or source rocks of oils also establish molecular parameters for palaeohypersalinity. Recently, ten Haven et al. (7-9) have summarized a number of "organic geochemical phenomena" related to hypersaline depositional environments. In addition to previously known parameters, such as an even-over-odd carbon number predominance of n-alkanes and a low pristane/ phytane ratio (<0.5), several new parameters were suggested. These parameters, however, are mainly based on empirical relations. 

Shi, W., Sun, M.Y., Molina, M., and Hodson, R.E. (2001) Variability in the distribution of lipid biomarkers and their molecular isotopic composition in Altamaha estuarine sediments implications for the relative contribution or organic matter from various sources. Org. Geochem. 32, 453-468. 

Petroleum hydrocarbon sources to North American and worldwide waters were summarized in a report by NRC (2002). In many cases of large petroleum spills, the specihc source of petroleum spill is evident, and no geochemical fingerprinting is required to establish the source. Nevertheless, the inventory of petroleum compounds and biomarkers that are eventually sequestered in bottom sediments need not reflect sole derivation from a single source, even in cases of massive oil spills in the area (e.g., Kvenvolden et al., 1995 Wang et al., 1999). Where a mass balance of petroleum sources is required to properly design remediation or identify a point source, molecular methods for distinguishing sources of hydrocarbons have come to the fore. 

Infrared and Raman spectroscopy, coupled with optical microscopy, provide vibrational data that allow us to chemically characterise geochemical sediments and weathered samples with lateral resolutions of 10-20 pm and 1-2 pm respectively. Fourier transform infrared spectroscopy involves the absorption of IR radiation, where the intensity of the beam is measured before and after it enters the sample as a function of the light frequency. Fourier transform infrared is very sensitive, fast and provides good resolution, very small samples can be analysed and information on molecular structure can be obtained. Weak signals can be measured with high precision from, for example, samples that are poor reflectors or transmitters or have low concentrations of active species, which is often the case for geochemical sediments and weathered materials. Samples of unknown... 

Ishiwatari, R. (1971). Molecular weight distribution of humic acids from lake and marine sediments. Geochem. J. 5, 121-132. 

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