DISSOLVED ORGANIC-CARBON IN MARINE PORE WATERS - A COMPARISON OF 3 OXIDATION METHODS

Three methods for oxidizing dissolved organic carbon (DOC) in pore waters of marine sediment from Cape Lookout Bight, North Carolina are compared: (1) high temperature (850-degrees-C) sealed tube combustion (STC) of salts following vacuum distillation; (2) high temperature catalytic combustion (HTCC) using a Shimadzu TOC-500 Total Carbon Analyzer; (3) low temperature chemical oxidation (LTCO) with peroxydisulfuric acid in sealed glass ampoules. The STC method is sufficiently robust to oxidize refractory compounds such as diamond and graphite. Direct comparison with a Carlo Erba Elemental Analyzer established that the STC technique is capable of quantitatively oxidizing organic carbon contained in the sediment solid phase. Pore water DOC concentrations determined by STC and HTCC generally agree within the analytical error of the methods. The fraction of the DOC reservoir resistant to LTCO is less than 10%, indicating that these pore waters do not contain a large pool of DOC that is resistant to chemical oxidation.