A simple rate model for organic matter decomposition in marine sediments

Abstract

A model is presented for the decomposition of organic matter in marine sediments. The model considers the organic matter as a whole. In this model the first-order rate parameters (k) gradually decrease with time (t) according to logk = −0.95 logt − 0.81 (N= 140; r = 0.987). This equation is found to be valid over eight orders of magnitude and is based on organic carbon versus depth profiles of well-dated cores and laboratory experiments. The predicted continuous decrease in the reactivity of organic matter is consistent with multi-G models and in situ measurements of sulphate reduction.Although all organic carbon versus depth profiles follow the same reactivity decrease with time, their reactivity at the sediment-water interface (i.e., “apparent initial age”) is different. Apparent initial ages calculated on the basis of various experiments and field measurements show consistent trends.