Microplastics influence on Hg methylation in diverse paddy soils

Area of Science:

• Environmental Science
• Soil Science
• Environmental Chemistry

Background:

• Microplastics are pervasive environmental contaminants.
• Mercury (Hg) methylation in paddy soils is a significant environmental concern.
• The impact of microplastics on mercury methylation in diverse soil types remains under-investigated.

Purpose of the Study:

• To investigate the influence of polyvinyl chloride microplastics (PVC-MPs) on mercury methylation in red and alkaline paddy soils.
• To determine the mechanisms by which PVC-MPs affect bioavailable methylmercury (MeHg) concentrations.

Main Methods:

• A microcosmic experiment was conducted using red and alkaline soils with varying concentrations of PVC-MPs (2%, 7%, 10%).
• Diffusive gradients in thin film (DGT) technique was employed to measure bioavailable Hg2+ and MeHg.
• Soil properties, DOM composition, microbial abundance (Proteobacteria, Firmicutes), and hgcA gene were analyzed.

Main Results:

• PVC-MPs significantly decreased bioavailable MeHg concentrations in both soil types.
• PVC-MPs altered dissolved organic matter (DOM) composition, affecting Hg2+ binding capacity.
• Changes in soil properties (sulfate, dissolved Fe) and microbial communities were observed, correlating with MeHg reduction.

Conclusions:

• Polyvinyl chloride microplastics can mitigate methylmercury levels in paddy soils through multiple mechanisms.
• Understanding microplastic-contaminant interactions is essential for developing effective remediation strategies for polluted soils.
• Further research is needed to elucidate the complex interactions between microplastics, mercury, and soil biogeochemistry.