The inertness of being organic

Organic matter protection, defined here as slowing of the oxidation of organic matter, is thought to result from a variety of mechanisms, which can be placed into two classes. Recalcitrant organic-organic linkages often account for protection on shorter time scales; biota intentionally create many of these linkages, leading to “selectively preserved” organic matter, and various humification reactions may produce others. On longer time scales, exclusion of biota or their digestive agents accounts for most protection, induced by factors such as clay mineral protection and anoxia. Longer term protection likely proceeds through a succession of different mechanisms, acting cooperatively. The papers of this session address kinetic and structural aspects of organic matter protection, in response to factors such as the hydrochemical cycle, organomineral aggregates, molecular aspects of nitrogen, and exposure to oxygen.