Sunlight plays an important role in transforming effluent organic matter as wastewater effluents travel downstream, but the corresponding effects on the formation of haloacetonitriles (HANs), a group of toxic disinfection byproducts, in wastewater-impacted surface water have not been thoroughly investigated. In this study, we observed that sunlight preferentially attenuated the formation potential of bromochloroacetonitrile (BCAN-FP) over that of dichloroacetonitrile (DCAN-FP) in chlorine- and UV-disinfected secondary effluents. For four effluent samples from different plants, 36 h of irradiation by simulated sunlight removed 28-33% of DCAN-FP and 41-48% of BCAN-FP. Across a larger set of effluent samples (n = 18), 8 h of irradiation (equivalent to 2-3 d of natural sunlight) decreased the calculated cytotoxicity contributed by dihaloacetonitrile-FP in most samples. Similar behavior was observed for a mixture of wastewater and surface water (volume ratio 1:1). For UV-disinfected effluents, the higher the UV dose, the more likely was there a reduction in DCAN-FP and BCAN-FP in the subsequent sunlight irradiation. Experiments with model compounds showed that fulvic acid and UV photoproducts of tryptophan yield excited triplet-state organic matters during sunlight irradiation and play an important role in promoting the attenuation of HAN precursors.

中文翻译：

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日光对废水中二氯乙腈和溴氯乙腈形成潜力的影响。

随着废水向下游移动，阳光在转化废水有机物方面起着重要作用，但尚未对废水影响的地表水中卤代乙腈（HANs）（一种有毒的消毒副产物）的形成的相应影响进行彻底研究。在这项研究中，我们观察到，在氯和紫外线消毒后的二级污水中，阳光比二氯乙腈（DCAN-FP）优先减弱了溴氯乙腈（BCAN-FP）的形成潜力。对于来自不同工厂的四个废水样品，模拟日光照射36 h去除了28-33％的DCAN-FP和41-48％的BCAN-FP。在更大范围的废水样本中（n = 18），辐照8小时（相当于2-3天的自然日照）可降低大多数样品中由二卤代乙腈-FP贡献的计算的细胞毒性。对于废水和地表水的混合物（体积比为1：1），观察到类似的行为。对于紫外线消毒的废水，紫外线剂量越高，在随后的日光照射下DCAN-FP和BCAN-FP减少的可能性就越大。用模型化合物进行的实验表明，色氨酸的富夫酸和紫外线光产物在阳光照射下会激发三重态有机物，并在促进HAN前体的衰减中起重要作用。在随后的日光照射下，DCAN-FP和BCAN-FP降低的可能性更大。用模型化合物进行的实验表明，色氨酸的富夫酸和紫外线光产物在阳光照射下会激发三重态有机物，并在促进HAN前体的衰减中起重要作用。在随后的日光照射下，DCAN-FP和BCAN-FP降低的可能性更大。用模型化合物进行的实验表明，色氨酸的富夫酸和紫外线光产物在阳光照射下会激发三重态有机物，并在促进HAN前体的衰减中起重要作用。