DISSOLVED ORGANIC-CARBON CONCENTRATIONS IN MARINE PORE WATERS DETERMINED BY HIGH-TEMPERATURE OXIDATION

We have developed sampling methods and an analytical system to determi ne the concentration of dissolved organic C (DOC) in marine pore water s. Our analytical approach is a modification of recently developed hig h-temperature, Pt-catalyzed oxidation methods; it uses chromatographic trapping of the DOC-derived CO2, followed by reduction to CH4 and fla me ionization detection. Sampling experiments with nearshore sediments indicate that pore-water separation by whole-core squeezing causes ar tificially elevated DOC concentrations, while pore-water recovery by s ectioning and centrifugation does not appear to introduce DOC artifact s. Results from a set of northwestern Atlantic continental slope cores suggest that net DOC production accounts for >50% of the organic C th at is recycled at the sediment-water interface.