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¯ow 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 identi®ed to be responsible for major turnover rates. A secondary process of sul®de oxidation by ironand manganese (hydr)oxides explained a distinctive sul®de sink. Iron and manganese minerals were removed from the solid phase by reduction. While the iron released in the process completely precipitated again forming sul®des and carbonates, some manganese was removed from the system. Only one proportion of dissolved manganese precipitated to form carbonates.