Increase in acetate concentrations during sediment sample onboard storage: a caution for pore-water geochemical analyses

Abstract

567 The concentration and carbon isotopic composition (δ13C) of acetate in marine sediment are such recent additions to the pore-water geochemical analyses, following the technological advancement of a sensitive analytical tool (Heuer et al., 2006), which was developed to understand subseafloor biogeochemical processes via acetate. It has been pointed out that acetate in sediment could be sensitive to a temperature increase, resulting in increased acetate concentrations after incubation of sediment at high temperature (Wellsbury et al., 1997). In this brief note, we simulated two possible cases of shipboard sample processing; i) short-term storage of the corer with rubber stoppers in a refrigerator at near in-situ temperature (4°C) until pore water extraction to minimize air contamination and temperature change represents an ordinarily procedure on board, even though a small temperature change from the absolute in-situ temperature to 4°C and air contamination is unavoidable, ii) storage at room temperature for 19 hours represents a worst possible condition. Such a worst case occasionally occur to cut core samples which have to be warmed to room temperature for non-destructive measurement of physical properties using a multi-sensor core logger (MSCL) for 12–17 hours before pore-water extraction (Ijiri et al., 2012). Those two samples have been provided to meaIncrease in acetate concentrations during sediment sample onboard storage: a caution for pore-water geochemical analyses