5 Chemical and Biological Processes Controlling DOC Concentrations

Concentrations of DOC in groundwater systems are affected by numerous chemical processes including adsorption, desorption, biodegradation, biosynthesis by microorganisms, and a variety of interactions with aquifer mineralogy. In general, these processes tend to remove DOC as groundwater flows downgradient away from recharge areas. The fact that measurable DOC concentrations are still present in groundwater that has traveled hundreds of kilometers in the subsurface reflects the many potential sources of autochthonous DOC that were discussed in Section 3.2, Autochthonous Sources of DOC. This section provides an overview of various chemical and biological processes that affect DOC concentrations in groundwater systems.