Mechanisms of reactive intermediates formation in saline-alkali agricultural waters

Reactive intermediates (RIs) are critical in nutrient cycling and pollution mitigation, yet their behavior in salinized agricultural waters remains underexplored. This study investigates RIs formation in rice cultivation water from a typical saline-alkali region in China. Singlet oxygen was more pH-sensitive than hydroxyl radical (•OH), while triplet excited-state dissolved organic matter were more influenced by salinity. Steady-state •OH concentration ([•OH]_ss) correlated strongly with concentrations of nitrite ([NO₂^--N]) and nitrate ([NO₃^--N]), with photolysis of NO₂^- and NO₃^-, and DOM contributing 19.50 %, 6.93 %, and 73.57 % to •OH formation, respectively. [RIs]_ss positively correlated with fluorescence index and negatively with autochthonous index, indicating exogenous DOM as a major RIs source. Additionally, [•OH]_ss was linked to aromatic content and DOM molecular weight, highlighting the importance of DOM structure in •OH production. These findings clarify the formation pathways of RIs in saline-alkali waters, informing ecological restoration and environmental management.