9633230 Mayer A pore protection hypothesis will be tested, provide a mechanistic basis for the observed patterns of organic carbon. Relationships between organic matter and mineral surfaces will be developed by: (1) Assessing the extent of organic matter coverage on mineral grains. Is organic carbon localized in small areas or is it widely dispersed? Wide dispersal implies that major fraction must reside in small pores. This question will be tested by completing development of a promising new method based on the of gas adsorption onto mineral surfaces. Completion work will focus on the nature of naked mineral surfaces, identifying variations that derive from mineralogy, microtopography, and source area; (2) Determining if natural organic matter resides preferentially inside small mesopores, by careful examination of the effects of removal of organic coatings on the size distribution of pores. This test will also involve the reverse process of adding artificial organic coatings to uncoated mineral grains, providing insight into the localization and mechanism of organic matter sorption. (3) Testing if these small mesopores on mineral grains can indeed exclude hydrolytic enzymes, by performing a series of size- exclusion and adsorption experiments. These approaches will be carried out on a wide variety of sediments from around the world. In addition to testing the pore hypothesis, results from this project will have important implications for carbon cycling, mineral-water interactions, and pollutant cycling.
