The influence of advective transport on redox fronts in column experiments and their numeric modeling. Part 2: modeling of the solid phase and secondary redox reactions

Abstract.

This study deals on the interrelation of redox processes in pore waters and solid phases. Therefore, a column experiment was carried out with sediments from an anoxic aquifer. The experiment was run for 80 weeks. Test water contained a constant concentration of the reducing agent acetate and was pumped through the column at a flow velocity of 0.80 m/day. Data were processed and interpreted by a combined approach of transport and reaction modeling. The primary redox processes oxygen-, nitrate-, iron- and sulfate-reduction were identified to be responsible for major turnover rates. A secondary process of sulfide oxidation by iron- and manganese (hydr)oxides explained a distinctive sulfide sink. Iron and manganese minerals were removed from the solid phase by reduction. While the iron released in the process completely precipitated again forming sulfides and carbonates, some manganese was removed from the system. Only one proportion of dissolved manganese precipitated to form carbonates.