Showing items related by title, author, creator and subject.

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  Preparation of Inorganic and Organic Carbon for 14 C Analysis from a Single Marine Sample

  Griffin, Sheila; Druffel, Ellen R. M. (Department of Geosciences, The University of Arizona, 1998-01-01)

  We have developed a technique using a single apparatus to recover the inorganic and organic carbon from a small (few milligrams) aliquot of dried marine material for radiocarbon analysis. The main advantages of using a single apparatus are: 1) less sample is required, 2) decreased handling reduces contamination, and 3) less time and materials are used. Blank values of approximately 5 micrograms and 19-44 micrograms are obtained for the inorganic and organic carbon extractions, respectively. Delta-14C results from sinking particulate organic and inorganic carbon are presented for samples collected in deep-sea sediment traps deployed for 10-30 day periods at 650 and 100 m above bottom (mab) in the northeast Pacific Ocean.
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  A Method for Quantifying Deep-Sea Carbonate Dissolution Using 14C Dating

  van Kreveld, S. A.; Ganssen, G. M.; van der Plicht, J. E.; Melkert, M. M.; Troelstra, S. R.; van der Borg, K.; de Jong, Arie (Department of Geosciences, The University of Arizona, 1995-01-01)

  We quantified the rate of carbonate dissolution with increasing water depth by taking the difference in the carbonate mass accumulation rate of deep (3393-4375 m) core top sediments from the shallowest one (3208 m), which we assumed was unaffected by dissolution. This method depends on high quality 14C dates that we calibrated to calendar years for calculating sedimentation rates. Our results show low (ranging from 0 to 0.3 g cm-2 ka-1) and high (ranging from 1.5 to 1.7 g cm-2 ka-1) carbonate dissolution rates, above and below 4000 m, respectively. Therefore, we interpret the sudden increase in the carbonate dissolution rate at 4000-m water depth to mark the lysocline.
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  Carbon Isotope Analysis of Land Snail Shells: Implications for Carbon Sources and Radiocarbon Dating

  Goodfriend, Glenn A.; Hood, Darden G. (American Journal of Science, 1983-01-01)

  13C and 14C analyses were performed on a series of modern Jamaican land snails in order to quantitatively determine the sources of shell carbon. A model of these carbon sources, the pathways by which carbon reaches the shell, and the fractionation processes involved are presented. The contribution of limestone to shell carbonate is variable but may comprise up to 33% of the shell. About 25-40% of shell carbonate is derived from plants and about 30-60% from atmospheric CO2. Variation among populations and species with respect to 13C and 14C is attributed to the effects of limestone incorporation, snail size (as it affects CO2 exchange rate), physiological characteristics (presence of urease, respiration rate), and activity patterns of the snails. A formula for correction for isotopic fractionation of 14C of shell carbonate, based on "C measurements, is derived. Bicarbonate-aragonite fractionation is apparently very minimal. Shell organic carbon appears to be derived largely from plants but also to a lesser extent from inorganic hemolymph carbon. This introduces the possibility of a small age anomaly of shell organic 14C due to limestone incorporation.