Iron, sulfur and trace metals geochemistry during redox oscillations in freshwater re-flooded acid sulfate soil wetlands

This thesis examined three important aspects of Fe and S biogeochemistry in freshwater re-flooded ASS wetlands with cyclic redox oscillations, (i) the stability of RIS and Fe species (ii) short- and long-term changes in Fe and S speciation and trace metals behaviour during drought and (iii) transformation of jarosite and subsequent behaviours of As and Sb, in these wetlands. The findings suggest a 2-3 weeks drought, can lead to the quick release of H⁺ with a potential for rapid pH recovery following re-flooding. This research also suggests lepidocrocite, GR-SO4 and goethite can scavenge As(V)/ Sb(V) under Fe²⁺-rich, circumneutral pH conditions.