The impact of rainwater-borne HO-induced Fenton process on root iron plaque formation and arsenic accumulation in rice.

Arsenic (As) contamination is a global concern, especially in paddy fields, as it represents a significant pathway for As reaching in the food chain. This is primarily due to the high accumulation of As in rice grains, which is a staple food for billions of people globally. Here we investigated the effect of synthetic rainwater-borne hydrogen peroxide (HO)-induced Fenton oxidation process in paddy soil on As uptake and speciation in rice plants at different growth stages. Results showed that adding Fenton reagents significantly accelerated root iron (Fe) plaque formation, thereby enhancing As retention in soil. Arsenic accumulation in different rice plant parts followed the order: Fe plaque > root > stem > leaf. In rice grains, inorganic As and dimethylarsinic acid (DMA) were the major As species for the first and second-season crops. Notably, that the addition of Fenton reagents to paddy soil led to a significant reduction in As accumulation in rice grains. The synthetic rainwater-borne HO-induced Fenton reaction significantly promoted As(V) precipitation and decreased concentration of the dissolved As in soil porewater. The current study highlights that the HO-induced Fenton process is an important pathway decreasing As bioavailability in paddy soil and its accumulation in rice grain. The findings have implications for understanding As behavior in paddy fields receiving rainwater-borne HO and for developing cost-effective remediation programs to reduce As accumulation in rice grains.