『Abstract
The three-way correlation among organic matter concentrations,
specific surface area and small mesopores observed for many soils
and sediments led to the hypothesis that enclosure within the
pores might explain the apparent protection of organic matter
by minerals. We test this hypothesis by examining whether the
bulk of organic matter resides within small mesopores. Pore volumes
as a function of pore width were measured before and after organic
matter removal, and the volume differences ascribed to organic
matter filling of pores. Minor changes in small mesopore size
distributions upon treatments such as centrifugation and muffling
indicate the robustness of the mineral matrices that form these
pores. We developed an additional method to assess organic matter
densities using high-resolution pycnometry, and used these densities
to convert pore volumes to organic matter contents. Although smaller
mesopores are shown to have sufficient volumes to contain significant
fractions of the total organic matter, only small fractions of
total organic matter were found to reside in them. These results
are consistent with preferential association between organic matter
and aluminous clay particle edges, rather than the largely siliceous
clay faces that contribute most surface area and form pore walls.
While simple enclosure within smaller mesopores cannot, therefore,
explain protection, network effects working at larger size scales
may account for exclusion of digestive agents and hence organic
matter protection.』
1. Introduction
2. Material and methods
3. Results
3.1. Analytical considerations
3.2. Cumulative volume distributions
3.3. Organic matter density
4. Discussion
4.1. Analytical considerations
4.2. Pore filling by organic matter
5. Conclusions
Acknowledgments
References