Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China; Engineering Research Center for Water Pollution Source Control & Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China; Engineering Research Center for Water Pollution Source Control & Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
Sci Total Environ. 2022 Oct 10;842:156692. doi: 10.1016/j.scitotenv.2022.156692. Epub 2022 Jun 23.
Nitrogenous disinfection by-products (N-DBPs) raise increasing concerns because of their high genotoxicity, cytotoxicity, and carcinogenicity compared to carbonaceous disinfection by-products (C-DBPs). Nitrogen-containing disinfectants, dissolved organic nitrogen (DON), and inorganic nitrogen may all promote the formation of N-DBPs. Therefore, it is urgent to explore the dominant nitrogen source of N-DBPs under the coexistence of multiple nitrogen sources. In this study, the effects of amino acids, nitrate, ammonia, and chloramine as different types of nitrogen sources on the formation of five N-DBPs were investigated systematically, including chloroacetonitrile (CAN), dichloroacetonitrile (DCAN), bromochloroacetonitrile (BCAN), dibromoacetonitrile (DBAN) and dichloroacetamide (DCAcAm). L-Aspartic acid (L-Asp) as the organic nitrogen source showed a high potential on the formation of N-DBPs by forming acetonitrile intermediates. Ammonia as the inorganic nitrogen source consumed oxidants and changed the existing form of chloramine, thus inhibiting the formation of N-DBPs. Instead of providing nitrogen to N-DBPs, nitrate as a salt promoted the volatilization of N-DBPs, thereby reducing the detected N-DBPs. Furthermore, an isotope labeling method was applied to clearly trace the nitrogen sources of N-DBPs via GC-MS with electron ionization. N-chloramine, N-amino acid, N-nitrate and N-ammonia were selected as the corresponding isotopic nitrogen sources. The results indicated that chloramine was the major nitrogen contributor to five N-DBPs during the chloramination of L-Asp under the coexistence of multiple nitrogen sources, ranging from 61 % to 79 %. The influence of environmental factors (reaction time, pH, and bromide) on the formation of N-DBPs during chloramination was also investigated. There was competition between brominated N-DBPs and chlorinated N-DBPs in chloramination. With the increase of reaction time or bromine, the formation potentials of chlorinated N-DBPs gradually decreased, while brominated N-DBPs gradually increased. Moreover, higher pH inhibited the generation of N-DBPs.
氮素消毒副产物（N-DBPs）由于其遗传毒性、细胞毒性和致癌性高于碳质消毒副产物（C-DBPs），因此引起了越来越多的关注。含氮消毒剂、溶解有机氮（DON）和无机氮都可能促进 N-DBPs 的形成。因此，迫切需要在多种氮源共存的情况下探索 N-DBPs 的主要氮源。本研究系统地考察了氨基酸、硝酸盐、氨和氯胺作为不同类型氮源对五种 N-DBPs（氯乙腈（CAN）、二氯乙腈（DCAN）、溴氯乙腈（BCAN）、二溴乙腈（DBAN）和二氯乙酰胺（DCAcAm））形成的影响。L-天冬氨酸（L-Asp）作为有机氮源，通过形成乙腈中间体，对 N-DBPs 的形成具有很高的潜力。作为无机氮源的氨消耗氧化剂并改变氯胺的存在形式，从而抑制 N-DBPs 的形成。硝酸盐作为一种盐，没有为 N-DBPs 提供氮，反而促进了 N-DBPs 的挥发，从而降低了检测到的 N-DBPs。此外，通过气相色谱-质谱联用仪（GC-MS）采用同位素标记方法，利用电子电离清楚地追踪 N-DBPs 的氮源。选择 N-氯胺、N-氨基酸、N-硝酸盐和 N-氨作为相应的同位素氮源。结果表明，在多种氮源共存下，L-Asp 氯化过程中，氯胺是五种 N-DBPs 的主要氮源，占比 61%至 79%。还研究了环境因素（反应时间、pH 值和溴化物）对 N-DBPs 形成的影响。在氯化过程中，溴代 N-DBPs 和氯代 N-DBPs 之间存在竞争。随着反应时间或溴的增加，氯代 N-DBPs 的生成潜力逐渐降低，而溴代 N-DBPs 逐渐增加。此外，较高的 pH 值抑制了 N-DBPs 的生成。
