Effect of atmospheric H₂O₂ on arsenic methylation and volatilization from rice plants and paddy soil

Studies focusing on arsenic methylation and volatilization in paddy soil, aiming to limit bioaccumulation of arsenic (As) in rice grains, have attracted global attention. In this study, we explored three aspects of these topics. First, rainwater and trace H₂O₂ were compared for their influence on the arsenic methylation and volatilization of paddy soil in different rice growth stages. Second, the arsenic accumulation in different parts of rice was affected by rainwater and trace H₂O₂. Third, we determined whether rice fields were affected by rainwater and trace H₂O₂. The result showed that the rainwater or trace H₂O₂ irrigation caused As(III) to significantly decrease and As(V) to significantly increase in soil. A similar consequence occurred in the filling stage and mature stage of rice. The arsenic volatilization rates of the rainwater and trace H₂O₂ irrigation were significantly higher than the control, and the arsenic volatilization of rainwater irrigation was the highest (51.0 μg m^-2 d^-1) in the filling stage. Compared to the control, the total arsenic and iAs of treatments decreased by 14-41% and 12-32% respectively. Finally, we found that rainwater and trace H₂O₂ irrigation likely increased rice fields.