Selenium chemistry in amorphous iron (hydr)oxide-applied soil as influenced by redox potential (Eh) and pH

Geochemical Implications of CO2 Leakage Associated with Geologic Storage: A Review

“…Such effects further indicate that gas composition could have significant implications for the mobility of As and other redox-sensitive contaminants (e.g., V, U, Se and Cr) in the subsurface, since their mobility is strongly influenced by speciation (Abdelouas et al 1999;Lee and Hering 2005;Rashid et al 2002;Sasaki et al 2010;Nickson et al 2000;Noubactep et al 2008;Smedley and Kinniburgh 2002). In cases where gas composition favors a shift from more to less mobile species (e.g., As(III) or Cr(VI) to As(V) and Cr(III), respectively), CO 2 intrusion could be considered beneficial, while in cases where the alternative shift is favored, then CO 2 intrusion would be deleterious.…”

“…For example, many groundwater contaminants are redox-sensitive, or contained in redox-sensitive minerals Edmunds et al 1989). It is the dissolution and precipitation of these minerals that will drive the total aqueous concentrations of redox-sensitive contaminants (Abdelouas et al 1999;Lee and Hering 2005;Rashid et al 2002;Sasaki et al 2010;Nickson et al 2000;Noubactep et al 2008;Smedley and Kinniburgh 2002). Therefore, laboratory studies involving aquifer sediments and seeking to assess how CO 2 intrusion would impact the geochemistry of the aquifer should be conducted under redox and solution conditions relevant to that system.…”

“…While the concept that lowering pH could enhance the dissolution of aquifer minerals and increase aqueous concentrations of contaminants in groundwater is reasonable, in the case of sulfides or other redox-sensitive minerals, redox conditions would be expected to have the greatest effect on their precipitation and dissolution behavior (Abdelouas et al 1999;Lee and Hering 2005;Rashid et al 2002;Sasaki et al 2010;Nickson et al 2000;Noubactep et al 2008;Smedley and Kinniburgh 2002;Edwards et al 2000). Thus, considering the influence of CO 2 intrusion rate on both pH and Eh and their coupled effects on the beneficial and deleterious reactions in the subsurface would provide a more complete scenario of what to expect within a particular environment.…”