Climate change has resulted in increased use of pesticides and fertilizers in agriculture, leading to elevated pesticide and nitrate levels in aquatic ecosystems that receive agricultural runoff. In this study, we demonstrate that far-UVC (UV₂₂₂) photolysis of nitrate rapidly degrades four pesticides in surface water, with a degradation rate constant 37.1–144.75 times higher than that achieved by UV₂₅₄ photolysis of nitrate. The improved pesticide degradation is due not only to the enhanced direct photolysis by UV₂₂₂ compared to UV₂₅₄ but also to the increased generation of hydroxyl radicals (HO^•) and reactive nitrogen species (e.g., NO₂^• and ONOO^–) in the UV₂₂₂/nitrate process. We determined the innate quantum yields of nitrate photolysis at 222 nm and incorporated these values into a kinetic model, allowing for the accurate prediction of nitrate photodecay and reactive species generation. While reactive nitrogen species predominantly contribute to pesticide degradation in the UV₂₂₂/nitrate process, they also lead to the formation of nitration byproducts. Using stable isotope-labeled nitrate (¹⁵NO₃^–) combined with mass spectrometry, we confirmed that the nitration byproducts are formed from the reactive nitrogen species generated from nitrate photolysis. Additionally, we demonstrate that the UV₂₂₂/nitrate process increases the formation potential of highly toxic nitrogenous chlorinated products (e.g., trichloronitromethane) during postchlorination in real surface water.

中文翻译：

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硝酸盐的远紫外线光解产生的活性氮物质有助于农药降解和含氮副产物的形成


气候变化导致农业中杀虫剂和化肥的使用增加，导致接受农业径流的水生生态系统中的杀虫剂和硝酸盐含量升高。在这项研究中，我们证明了硝酸盐的远 UVC （UV₂₂₂） 光解可快速降解地表水中的四种农药，降解速率常数比 UV₂₅₄ 光解硝酸盐所达到的降解速率高 37.1-144.75 倍。农药降解的改善不仅是由于与 UV₂₅₄ 相比，UV₂₂₂ 的直接光解能力增强，而且是由于 UV₂₂₂/硝酸盐过程中羟基自由基 （HO^•） 和活性氮种类（例如 NO₂^• 和 ^ONOO–）的产生增加。我们确定了硝酸盐光解在 222 nm 处的固有量子产率，并将这些值纳入动力学模型，从而可以准确预测硝酸盐光衰和反应性物质的产生。虽然活性氮物质主要导致 UV₂₂₂/硝酸盐过程中的农药降解，但它们也会导致硝化副产物的形成。使用稳定同位素标记的硝酸盐 （¹⁵NO₃^–） 结合质谱法，我们证实硝化副产物是由硝酸盐光解产生的活性氮物质形成的。此外，我们还证明，UV₂₂₂/硝酸盐过程增加了在实际地表水中后氯化过程中剧毒含氮氯化产物（例如三氯硝基甲烷）的形成可能性。