Biochar amendment reduced methylmercury accumulation in rice plants

Area of Science:

• Environmental Science
• Agricultural Science
• Soil Science

Background:

• Methylmercury (MeHg) accumulation in rice grains poses a significant dietary risk in Asia.
• Understanding MeHg dynamics in soil-rice systems is crucial for mitigating human exposure.

Purpose of the Study:

• To investigate the efficacy of biochar amendment in reducing grain MeHg levels.
• To elucidate the underlying mechanisms responsible for MeHg reduction in rice.

Main Methods:

• Pot and batch experiments were conducted to assess MeHg dynamics under varying biochar amendment rates (1-4%).
• Evaluated MeHg production, partitioning, phytoavailability in paddy soils, and uptake by rice plants.

Main Results:

• Biochar amendment markedly decreased grain MeHg levels by 49-92%.
• Observed increased soil MeHg concentrations due to biochar-induced sulfate release and microbial activity.
• Biochar facilitated MeHg immobilization in soil via its large surface area and organosulfur content.
• Biodilution of MeHg in rice grains occurred due to enhanced grain biomass (35-79%) under biochar treatment.

Conclusions:

• Biochar amendment is a promising strategy for reducing MeHg accumulation in rice grains.
• Mechanistic insights reveal complex interactions between biochar, soil microbes, and MeHg dynamics.
• This approach can help mitigate dietary MeHg exposure in regions reliant on rice consumption.