Biogeochemical processes controlling contaminant transport and transformation in a hydrocarbon contaminated aquifer

Hydrocarbon spills that reach the subsurface modify aquifer geochemical conditions. Reducing organic mixtures that reach the subsurface modify the redox environment of a pristine aquifer, affecting both organic and inorganic groundwater chemistry. Important processes include dissolution/precipitation of minerals, complexation, ion exchange, sorption, and organic matter biodegradation.2 The introduced organic matter has a great capacity to donate electrons and is oxidized with corresponding reduction reactions including that of oxygen to water, nitrite to elementary nitrogen N2, manganese (III/IV) to manganese(II), iron(III) to iron(II), sulfate to sulfide, and CO2 to methane.3 The resulting redox changes associated with organic contaminant spills can result in metal (hydr)oxide reduction and subsequent release of naturally occurring contaminants to groundwater, particularly those with a strong sorption affinity to Fe(III) and Mn(IV) (hydr)oxides. Thus, the goal of the proposed research is to quantify the potential for release and transport of geogenic contaminants in a hydrocarbon impacted aquifer located near Cottage Grove, WI.