Elucidation of different forms of organic carbon in marine sediments from the Atlantic coast of Spain using thermal analysis coupled to isotope ratio and quadrupole mass spectrometry

12 páginas, 5 figuras, 3 tablas, 47 referencias.-- Advances in Organic Geochemistry 2005 — Proceedings of the 22nd International Meeting on Organic Geochemistry, Seville, Spain, 12-16 September 2005.-- [email protected] of river, estuary and marine sediments from the Atlantic coast of Spain using thermogravimetry–differential scanning calorimetry–quadrupole mass spectrometry–isotope ratio mass spectrometry (TG–DSC–QMS–IRMS) was used to (a) distinguish bulk chemical hosts for C within a sediment and humic acid fraction, (b) track C pools with differing natural C isotope ratios and (c) observe variation with distance from the coast. This is the first application of such a novel method to the characterisation of organic matter from marine sediments and their corresponding humic acid fractions. Using thermal analysis, a labile, a recalcitrant and a refractory carbon pool can be distinguished. Extracted humic fractions are mainly of recalcitrant nature. The proportion of refractory carbon is greatest in marine sediments and humic acid fractions. Quadrupole mass spectrometry confirmed that the greatest proportion of m/z 44 (CO2) and m/z 18 (H2O) were detected at temperatures associated with recalcitrant carbon (510–540 °C). Isotope analysis detected progressive enrichment in δ13C for the sediment samples with an increase in marine influence. Isotopic heterogeneity in the refractory organic matter in marine sediments could be due to products of anthropogenic origin or natural combustion products. Isotope homogeneity of humic acids confirms the presence of terrigenous C in marine sediments, allowing the terrestrial input to be characterised.This work has been carried out using financial support to D.A.C.M. from the EPSRC (GR/R34332/01), NERC (NER/D/S/2003/00678) and One NorthEast. Financial support to J.M. de la Rosa was obtained from the European Union Marie Curie postgraduate training programme. We would like to thank The Spanish Ministry of Education for providing funds for the BACH project (BC, REN 2002-04602-C02).Peer reviewe