Thermodynamic Modeling of Complex Sediment-Water-Gas Interactions During Early Diagenesis

The driving force of complex biogeochemical reactions in sedimentary environments during early diagenesis is the irreversible redox-conversion of organic matter. Our modeling approach incorporates interdependent diagenetic reactions evolving into a diffusive multi-component and multi-phase system by means of thermodynamic equilibrium calculations of species distribution. The modeling tool is the PHREEQC (version 2) computer code. Reaction kinetics of organic carbon conversion are integrated into the set of equilibrium reactions by defining the type and amount of converted organic matter at a certain time step. The model has been applied so far in different environmental settings: the gas hydrate dominated sediments of Hydrate Ridge (ODP Leg 204), the high accumulation area of the Amazon Fan, and the upwelling area off Peru.