Jining Li

Arsenic (As) contamination and methane (CH ₄ ) emissions are major environmental concerns in flooded paddy fields. Microscale zero-valent iron is widely used for As immobilization owing to its high affinity for As, yet its effects on CH ₄ cycling and the underlying microbial mechanisms remain poorly understood. This study explored coupled responses of As mobility, rice As accumulation and CH ₄ dynamics to mZVI via microcosm incubation and rice-planting trials. mZVI substantially lowered As mobility by altering soil As speciation. It also promoted the stabilization of As in Fe-bound fractions. Magnetic separation further verified that aging ZVI-derived Fe minerals contributed to As sequestration, with magnetic fractions containing 3.23-fold higher As concentrations than non-magnetic solids. Accordingly, mZVI markedly decreased As accumulation in rice roots, stems, leaves, and grains by 83.3%, 92.9%, 87.4%, and 34.0%, respectively. It also reduced grain inorganic As(V) and dimethylarsinic acid by 68.2% and 77.3%, respectively. However, the environmental benefits of mZVI for As remediation were accompanied by enhanced CH ₄ emissions. Compared with the control, mZVI accelerated CH ₄ production during anaerobic incubation. This enhancement was associated with improved methanogenic potential, as indicated by increased mcrA abundance and enrichment of key methanogenic genera, including Methanobacterium, Methanocella, and Methanosarcina. Despite enhanced methane oxidation potential with higher pmoA and enriched type-II methanotroph Methylocystis, such promotion could not counteract intensified methanogenesis. Overall, our findings demonstrate that zero-valent iron amendment creates a trade-off between effective As remediation and increased CH ₄ emissions in paddy soils. The results highlight the necessity of integrating greenhouse gas mitigation strategies with iron-based remediation practices to achieve sustainable management of As-contaminated rice ecosystems.

With the continuous advancement of global industrialization, a large amount of organic and inorganic pollutants have been discharged into the environment, which is essential for human survival. Consequently, the issue of water environment pollution has become increasingly severe. Photocatalytic technology is widely used to degrade water pollutants due to its strong oxidizing performance and non-polluting characteristics, and BiVO₄-based photocatalysts are one of the ideal raw materials for photocatalytic reactions. However, a comprehensive global analysis of the factors influencing the photocatalytic performance of BiVO₄-based photocatalysts is currently lacking. Here, we performed a meta-analysis to investigate the differences in specific surface area, kinetic constants, and the pollutant degradation performance of BiVO₄-based photocatalysts under different preparation and degradation conditions. It was found that under the loading condition, all the performances of the photocatalysts can be attributed to the single BiVO₄ photocatalyst. Moreover, loading could lead to an increase in the specific surface area of the material, thereby providing more adsorption sites for photocatalysis and ultimately enhancing the photocatalytic performance. Overall, the construct heterojunction and loaded nanomaterials exhibit a superior performance for BiVO₄-based photocatalysts with 136.4% and 90.1% improvement, respectively. Additionally, within a certain range, the photocatalytic performance increases with the reaction time and temperature.