Geochemical cycles of organic compounds in terrestrial-marine environments using compound-specific carbon isotope ratios

Carbon isotopic compositions of lipid biomarkers from marine sediments and terrestrial plants weredetermined using gas c h r o m a t o g r a p h y / combustion / isotope-ratio mass spectrometry (gc / c / irms) . atfirst,derivatization of non-volatile compounds and separation of straight-chain compounds using urea适用于isotope measurements. Terrestrial biomarkers such ascutin-derived fatty acids （w- and di- hydroxy carboxylic acids）和lignin-derived phenols areD1C by several per mil relative to bulk organic carbon.Carbon isotope ratios ofsedimentary cutin-derived acids in East China Sea and Yellow Sea are consistent with C3 plants in East China Sea and Yellow Sea are consistent with C3 plants intheir origins On the other hand，co-existent long-chain n-alkanoic acids (>C - D220 - D2) never derived from C3 plants，but from C4 and C3 plant mixing (mainly C4) or marine biological activities. Such isotopicdistributions are quite similar to their sedimentary isotope signatures of the Pacific Ocean andJapan Sea. Isotopic and molecular results may indicate that long-chain n-alkanoic acids in themarine sediments have marine origins，虽然他们已经使用了作为一个terrestrial biomarker.Carbon isotopic compositions of individualbiomarkers are useful means to study biomarker origins as as transportation processes andgeochemical cycles of organic compounds.他们也可以应用于生态和paleoenvironmental studies。

Carbon isotopic compositions of lipid biomarkers from marine sediments and terrestrial plants were determined using gas chromatography/combustion/isotope-ratio mass spectrometry (GC/C/IRMS). At first, derivatization of non-volatile compounds and separation of straight-chain compounds using urea adduction were tested and established for the isotope measurements. Terrestrial biomarkers such as cutin-derived fatty acids (w- and di- hydroxy carboxylic acids) and lignin-derived phenols are depleted in ィイD113ィエD1C by several per mil relative to bulk organic carbon.Carbon isotope ratios of sedimentary cutin-derived acids in East China Sea and Yellow Sea are consistent with C3 plants in their origins. On the other hand, co-existent long-chain n-alkanoic acids (>CィイD220ィエD2) were never derived from C3 plants, but from C4 and C3 plant mixing (mainly C4) or marine biological activities. Such isotopic distributions are quite similar to their sedimentary isotope signatures of the Pacific Ocean and Japan Sea. Isotopic and molecular results may indicate that long-chain n-alkanoic acids in the marine sediments have marine origins, although they have been used as a terrestrial biomarker.Carbon isotopic compositions of individual biomarkers are useful means to study biomarker origins as well as transportation processes and geochemical cycles of organic compounds. They also can be applied to ecological and paleoenvironmental studies.