Although the photochemical behavior of surface water and its effects on pollutant transformation have been studied extensively in recent years, the photochemistry of paddy water remains largely unknown. In this study, we examined the photochemical processes involving paddy water samples collected at four different cultivation stages of rice. Triplet dissolved organic matter (³DOM*), singlet oxygen (¹O₂), and hydroxyl radicals (^•OH) were found to be the dominant reactive intermediates (RIs), and their apparent quantum yields and steady-state concentrations were quantified. Compared with the typical surface water, quantum yields of ³DOM* and ^•OH were comparable, while quantum yields of ¹O₂ were about 2.4-6.7 times higher than those of surface water. Fluorescence emission-excitation matrix (EEM) spectra, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), and statistical analysis revealed that DOM properties and nitrite concentration were the main factor influencing RIs generation. The results suggest that DOM with lower molecular weight and humification extent generated more RIs, and nitrite contributed to 23.9%–100% of ^•OH generation. EEM and FTICR-MS data showed that DOM with more saturated and less aromatic formulas could produce more ³DOM* under the irradiation, while the polyphenolic components of DOM inhibited the formation of RIs. Moreover, RIs significantly enhanced arsenite (As(III)) oxidation with oxidation rate increased by 1.8–4.1 times in paddy water, and ^•OH and ³DOM* were the main RIs responsible for As(III) oxidation. This study provides new insight into the pathways of arsenite abiotic transformation in paddy soil and water.

尽管近年来对地表水的光化学行为及其对污染物转化的影响进行了广泛的研究，但稻田水的光化学在很大程度上仍是未知的。在这项研究中，我们研究了涉及在水稻四个不同栽培阶段收集的水稻水样的光化学过程。发现三重溶解有机物 ( ³ DOM*)、单线态氧 ( ¹ O ₂ ) 和羟基自由基 ( ^• OH) 是主要的反应中间体 (RI)，并且对它们的表观量子产率和稳态浓度进行了量化。与典型地表水相比，³ DOM* 和^{• 的}量子产率OH 具有可比性，而¹ O _{2 的}量子产率比地表水的量子产率高约 2.4-6.7 倍。荧光发射激发矩阵 (EEM) 光谱、傅里叶变换离子回旋共振质谱 (FTICR-MS) 和统计分析表明，DOM 特性和亚硝酸盐浓度是影响 RI 生成的主要因素。结果表明，具有较低分子量和腐殖化程度的 DOM 产生更多的 RI，亚硝酸盐贡献了 23.9%–100% 的^• OH 生成。EEM 和 FTICR-MS 数据表明，具有更多饱和和更少芳香配方的 DOM 可以产生更多的³DOM* 在辐照下，而 DOM 的多酚成分抑制了 RIs 的形成。此外，RI 显着增强了亚砷酸盐 (As(III)) 的氧化，在稻田水中的氧化速率增加了 1.8-4.1 倍，而^• OH 和³ DOM* 是负责 As(III) 氧化的主要 RI。这项研究为水稻土壤和水中亚砷酸盐非生物转化途径提供了新的见解。