Bromide ion (Br-) in water sources has been found to affect the formation of carcinogenic non-brominated N-nitrosodimethylamine (NDMA) during ozonation of typical amines. The increasing bromide levels bring more concern due to climate change and industrial discharge, but its effects on actual water matrixes were still unclear. In this study, NDMA formation from three actual water matrixes during ozonation as the Br- concentration increased from 0 to 100 µM were investigated (promotion (100.4 ∼ 231.6 ng/L), promotion then inhibition (399.5 ∼ 461.2 ∼ 428.2 ng/L), and subtle influence (51.9 ± 6.9 ng/L)); from which the NDMA precursors were screened and 8 precursors were selected for exploring the influencing mechanisms. The results indicated that the roles of Br- on NDMA formation significantly depended on the water characteristics of actual matrixes. A total of 16 typical NDMA precursors, which were mainly derived from industrial, agricultural and pharmaceutical sources, were identified. Moreover, 6 brominated substance (Br-DMA, Br-UDMH, Br-DMSC, Br-DMS, Br-TMDS, Br2-TMDS), which were thought to play a crucial role in promoting NDMA formation, were also identified in actual water by precursor ion scan (PIS) method. Hypobromous acid (HOBr), which has been proved to be the culprit to the generation of brominated substances, tend to attack the electron-donating groups of amines, such as acylamino (–NHCO-R) or amidogen (–NH2) groups. However, the reactive bromine species (∙Br and ∙Br2-) was inclined to attack the aromatic and anti-oxidant moieties then result in Br- release, as no bromine substitution but free radical transfer reaction occurs. Therefore, decreasing HOBr formation is the crucial step to reduce NDMA generation. This work would provide technical guide for NDMA risks control during ozonation of Br--amines co-containing water matrixes.

中文翻译：

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揭示实际水基质臭氧化过程中 Br- on NDMA 形成的不同影响机制：前体和溴化物质的鉴定


已发现水源中的溴离子 （Br-） 会影响典型胺臭氧化过程中致癌非溴化 N-亚硝基二甲胺 （NDMA） 的形成。由于气候变化和工业排放，溴化物含量的增加引起了更多关注，但其对实际水基质的影响仍不清楚。在这项研究中，研究了当 Br- 浓度从 0 增加到 100 μM 时，臭氧化过程中三种实际水基质形成 NDMA（促进 （100.4 ∼ 231.6 ng/L）、促进然后抑制 （399.5 ∼ 461.2 ∼ 428.2 ng/L） 和微妙的影响 （51.9 ± 6.9 ng/L））;从中筛选出 NDMA 前体，筛选出 8 种前体，探究其影响机制。结果表明，Br- 对 NDMA 形成的作用显着取决于实际基质的水特性。共鉴定出 16 种典型的 NDMA 前体，主要来源于工业、农业和制药来源。此外，通过前体离子扫描 （PIS） 方法在实际水中鉴定了 6 种被认为在促进 NDMA 形成中起关键作用的溴化物质 （Br-DMA、Br-UDMH、Br-DMSC、Br-DMS、Br-TMDS、Br2-TMDS）。次溴酸 （HOBr） 已被证明是生成溴化物质的罪魁祸首，它往往会攻击胺的供电子基团，例如酰氨基 （–NHCO-R） 或氨基 （–NH2） 基团。然而，反应性溴种类（∙Br 和 ∙Br2-）倾向于攻击芳香族和抗氧化部分，然后导致 Br- 释放，因为没有溴取代，而是发生自由基转移反应。因此，减少 HOBr 的形成是减少 NDMA 生成的关键步骤。 这项工作将为共含 Br-胺类水基质臭氧化过程中的 NDMA 风险控制提供技术指导。