Factors affecting metal releases from contaminated marine sediments

In aquatic environments, the depth of oxygen penetration into sediment depends on sediment texture, porosity, permeability and the extent of biological (e.g., bioturbation) and physical (e.g., wave action) processes. Below the oxygen penetration depth (generally 10 mm) anoxic conditions prevail and bacteria use other oxidants such as iron and manganese oxides and sulfate to breakdown organic matter. The bacteria-catalysed reduction of sulfate releases hydrogen sulfide according to Equation 1. The release of H2S into the pore waters SO42- + bacteria → H2S (Equation 1).