Diagenesis (Pollutant)

Pollutant diagenesis is the set of chemical and microbial changes that contaminants undergo after burial in marine sediment. Early diagenesis runs through redox zones, oxic, then nitrate, manganese, iron, and sulfate reduction, then methanogenesis, as buried organic matter is remineralized. Anoxic conditions drive transformations that aerobic surface water does not: reductive dechlorination of PCBs and DDT, methylation of mercury to methylmercury by sulfate-reducing bacteria, and remobilization of metals when sulfides oxidize. These processes decide whether a buried contaminant is locked away, degraded, or released back to the water column.