6 Bioavailability of DOC in Groundwater Systems

Microbially mediated reduction/oxidation (redox) processes, many of which are driven by bioavailable organic carbon, affect the geochemistry and chemical quality of groundwater in both pristine and human-impacted aquifer systems. Methods for determining the bioavailability of particulate and adsorbed organic matter, which are by far the most abundant forms of carbon in groundwater systems, are analytically challenging to perform and difficult to apply in routine hydrologic investigations (Rectanus et al., 2007, Thomas et al., 2012, Chapelle et al., 2012b, Alicea, 2017). In contrast, methods for determining the bioavailability of dissolved organic carbon (DOC) are more straightforward and have been widely applied to groundwater systems (Cronan and Aiken, 1985, Qualls and Haines, 1992, Shen et al., 2015). Importantly, these studies have shown that the behavior of DOC in groundwater is not static, but it interacts continuously and somewhat reversibly with adsorbing aquifer materials such as particulate organic carbon (POC) and mineral surfaces (Davis, 1982; Jardine et al, 1989; Findlay et al., 1993; Hornberger et al., 1994; Findlay and Sobczak, 1996). That being the case, it is possible that the bioavailability of DOC may reflect the bioavailability of the associated POC and AOC compartments at any point in a groundwater flow system.


Dissolved Organic Carbon in Groundwater Systems Copyright © 2022 by Francis H. Chapelle. All Rights Reserved.