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Fe-oxide reduction, sulfate reduction and methanogenesis, have been studied in a shallow aquifer with the main focus on sulfate reduction. Direct measurements of sulfate reduction rates have for the first time been applied in an aquifer system. Rates were much lower than reported in other anoxic environments - three orders of magnitude lower than in marine settings and one order of magnitude lower than in lacustrine environments, and varied substantially mainly due to differences in the reactivity of the organic matter. At the extremely low substrate levels in the aquifer, sulfate reduction rates are not primarily limited by low sulfate concentrations. The produced sulfide forms framboidal pyrite via a FeS precursor, with elemental sulfur as an intermediate. Fe-oxide reduction rates were comparable to sulfate reduction rates, but appeared to depend more on Fe-oxide reactivity than organic matter reactivity. Low sulfate …