Carbon compounds radiocarbon measurements

The biomarker concept is a powerful tool for understanding the biogeochemistry when compounds have unique biological origin, but when multiple sources are identified for a given compound, interpretation can become more complex. Likewise stable isotope signals can be complicated because of mixed sources. However, radiocarbon measurement provides an additional important parameter to help evaluate source/age of the components (Druffel and Williams, 1990 Druffel et al, 1992). The combined biomarker/stable isotope/radiocarbon isotope approach should, therefore, offer a more comprehensive approach for resolving the complex marine carbon cycle. 

Stable carbon isotopes data—The data from stable isotope and radiocarbon measurements are summarized in Table 1. Analytical precision is 0.l%o for C. Stable carbon isotope ratios of the different fractions span from — 20.14 to — 27.82%o with the unextracted and extracted sediments exhibiting values, as expected, in the midrange around — 22%o (Fig. 1). The only exception is the fatty acid fraction which is anomalously depleted in Stable carbon isotope numbers of the different compound classes from the SMB samples, in general, suggest a mixing of terrestrial and marine components with humic and fidvic acids implying major contribution from marine sources (Sweeney and Kaplan, 1980 Stuermer et al., 1978). 

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