To better understand the influence of heavy precipitation event on water supply security, the change of nutrients, dissolved organic matter (DOM) and their corresponding disinfection by-products (DBPs) generation in river were investigated through a heavy precipitation event. The results show that short-term sustained heavy precipitation causes additional load on the river. Significant temporal variations and increases in dissolved oxygen (DO), turbidity, dissolved organic carbon (DOC) and molecular weight of raw water were observed during the heavy precipitation, and dissolved organic nitrogen (DON) showed a remarkably decline with the continuation of precipitation. The molecular weight and aromaticity of DOM increased dramatically with the continuous superposition of precipitation and flow, and the proportion of hydrophobic fraction increased during the study period. Four different fluorescent components were identified, including humic-like (C1, C2 and C3), and protein-like fluorophore C4. Heavy precipitation events affected the mobilization of DOM, while the generation of DBPs increased by 4%–47% during the chlorination, and the elevated river level further increased the DBPs formation. In particular, the HOA fraction was the main contributor of DBPs (up to 70%). The risk of haloacetic acids (HAAs) generation caused by heavy rainfall was concentrated in the river runoff producing and regression periods for both hydrophobic and hydrophilic fractions of DOM. Humification index (HIX) was positively correlated with the yield level of TCM, DCAA, TCAA, and DCAN during chlorination. Chlorination disinfection of raw water during river runoff producing and regression period is likely to increase the haloacetonitriles formation potential (HANsFP), thus posing a vital threat to water supply safety, while chloramination disinfection may significantly relieve the threat. This study provides a theoretical basis for the direct/indirect link between short-term precipitation events and their impact on water quality.

中文翻译：

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强降水事件对水源水质的响应：营养物、溶解有机物及其 DBP 形成

为了更好地了解强降水事件对供​​水安全的影响，通过一次强降水事件调查了河流中营养盐、溶解有机物（DOM）及其相应消毒副产物（DBPs）生成的变化。结果表明，短期持续强降水对河流造成额外负荷。在强降水过程中，原水溶解氧（DO）、浊度、溶解有机碳（DOC）和分子量均出现显着的时间变化和增加，而溶解有机氮（DON）则随着降水的持续而显着下降。研究期间随着沉淀和流动的不断叠加，DOM的分子量和芳香度急剧增加，并且疏水部分的比例增加。鉴定出四种不同的荧光成分，包括类腐殖质（C1、C2 和 C3）和类蛋白质荧光团 C4。强降水事件影响了DOM的动员，而氯化过程中DBPs的生成量增加了4%~47%，且河流水位的升高进一步增加了DBPs的生成量。特别是，HOA 部分是 DBP 的主要贡献者（高达 70%）。暴雨引起的卤乙酸（HAAs）生成风险集中在河流径流产生和消退阶段，无论是DOM的疏水性部分还是亲水性部分。腐殖化指数（HIX）与氯化过程中TCM、DCAA、TCAA和DCAN的产量水平呈正相关。在河道径流产生和消退期间对原水进行氯化消毒可能会增加卤代乙腈的形成潜力（HANsFP），从而对供水安全构成重大威胁，而氯胺消毒可以显着缓解这一威胁。本研究为短期降水事件及其对水质影响之间的直接/间接联系提供了理论基础。