Black carbon in marine sediments

Concentrations of black carbon were determined for a number of marine sedim ents. A comparison of black carbon based on thermal oxidation and hot conce ntrated nitric acid pretreatments revealed that the latter significantly ov erestimates combustion derived carbon phases. Black carbon accounts for abo ut 15 to 30% of total organic carbon and therefore reduces the fraction of unidentified sedimentary organic carbon. Examination of a relict oxidation front in a Madeira Abyssal Plain turbidite provided the first evidence for significant black-carbon degradation (about 64%) in marine sediments given time (10-20 kyr) and oxygen exposure. (C) 1999 Elsevier Science B.V. All ri ghts reserved.