Mechanisms of POM-mediated Hg immobilization and MeHg suppression in paddy soil: a perspective of coupled geochemical and microbial processes under water management.

POM addition under flooded conditions reduces soil available Hg by up to 82% and suppresses MeHg accumulation through microbial and geochemical interactions.

• Why it matters: Understanding how POM influences Hg immobilization and methylmercury suppression is crucial for developing strategies to mitigate Hg bioavailability in contaminated soils, especially under water management practices.
• What they did: The study conducted a 120-day incubation experiment with batch adsorption, multi-technique characterization, and microbial analysis to examine POM's effects on Hg fractions, microbial communities, and gene abundance under non-flooded and flooded conditions.
• The result: POM immobilized Hg via physical entrapment and surface complexation, increased SOC contributing to Hg transformation, and dose-dependently reduced MeHg by lowering bioavailable Hg pools and enriching keystone microbes like Vicinamibacter, suggesting potential mitigation strategies needing field validation.