Charcoal analysis in marine sediments

A technique is described for measuring charcoal in small samples (5 mg) of marine sediments to quantify the contribution of charcoal to the total organic carbon loading of marine sediments. Charcoal is measured as elemental carbon by gas chromatography after acidification with hot concentrated nitric acid in situ within aluminum sample cups to remove calcium carbonate and refractory carbon such as coal, pollen, and humic acids. The in situ acidification eliminates sample loss during sequential decarboxylation and oxidation and provides a precise (+/-2.2% of the measured value) and rapid (similar to 50 analyses per week per analyst) means to measure charcoal in marine sediments. The absolute detection Limit of the charcoal determinations is 0.70 mu g C (3 times mean blank value) and the relative detection limit is 0.01%.