Our classic view of soil organic matter is that it is a penecontemporaneous mixture in which an aged, diagenetically altered component (humic material) is derived from previous inputs of photosynthetically-derived material. In reality, particulate organic carbon (POC) in surficial environments (both soils and sediments) is a mixture that can be fundamentally resolved into three general categories: contemporary (recently fixed C), aged (century to millennial time scale) and ancient (millions of years old). The relative abundances of these three C-pools are highly dependent on the environment and they evolve as particulates move across the landscape and bathyscape.

In this talk, a global-scale conceptual model will be presented that describes the behavior of these POC mixtures in coupled watershed-marine systems. The implications of this research within the context of global environment change will be considered.