Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Hohai University, Nanjing 210098, PR China; College of Environment, Hohai University, Nanjing 210098, PR China.
Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Hohai University, Nanjing 210098, PR China; College of Environment, Hohai University, Nanjing 210098, PR China.
Sci Total Environ. 2020 May 15;717:137205. doi: 10.1016/j.scitotenv.2020.137205. Epub 2020 Feb 8.
Soluble microbial products (SMPs), as precursors of disinfection byproducts (DBPs) in water treatment, are composed of polysaccharides, humic acid, proteins and DNA, and have caused widespread concerned. Pyrimidine bases (cytosine and thymine) are significant nitrogenous constituents of DNA, which could pose an adverse impact on water quality during chlorination. This study focused on the correlation between relative reactivity, formation of DBPs and combined toxicity in the chlorination of a binary pyrimidine base mixture. The relative reactivities of cytosine and thymine were quite different at a low disinfectant concentration; cytosine reacted more actively with chlorine than thymine did, at the chlorine/total pyrimidine bases molar ratio = 10. The chlorination of binary pyrimidine bases can produce both carbonous DBPs (C-DBPs) and nitrogenous DBPs (N-DBPs). In particular, the total yields of trichloromethane (TCM) and trichloronitromethane (TCNM) were lower than the additive yields of monadic cytosine and monadic thymine ("monadic" refers to "separate"), whereas the total yields of haloacetic acids (HAAs) and haloacetonitriles (HANs) were promoted evidently. High reactivity of cytosine with chlorine, greater potential of cytosine to produce specific DBPs and the alkylation of transformation products of thymine may synthetically account for the diversity in total DBPs yields, especially the increased formation of HAAs and HANs. In our toxicity trial, even though the antagonistic effect predominated at f > 0.4 (f refers to the affected fraction), the synergism at low concentration levels could enhance the combined toxicity by promoting the yields of N-DBPs.
可溶解性微生物产物（SMPs）作为水处理中消毒副产物（DBPs）的前体，由多糖、腐殖酸、蛋白质和 DNA 组成，引起了广泛关注。嘧啶碱基（胞嘧啶和胸腺嘧啶）是 DNA 的重要含氮成分，在氯化过程中可能对水质产生不利影响。本研究关注二元嘧啶碱基混合物氯化过程中相对反应活性、DBPs 生成和联合毒性之间的相关性。在低消毒剂浓度下，胞嘧啶和胸腺嘧啶的相对反应活性差异很大；在氯/总嘧啶碱基摩尔比=10 时，胞嘧啶比胸腺嘧啶更活跃地与氯反应。二元嘧啶碱基的氯化可以产生碳性 DBPs（C-DBPs）和氮性 DBPs（N-DBPs）。特别是三氯甲烷（TCM）和三氯硝基甲烷（TCNM）的总生成量低于单胞嘧啶和单胸腺嘧啶的加和生成量（“单”指“分开的”），而卤乙酸（HAAs）和卤乙腈（HANs）的总生成量明显增加。胞嘧啶与氯的高反应活性、胞嘧啶产生特定 DBPs 的更大潜力以及胸腺嘧啶转化产物的烷基化作用可能综合解释了总 DBPs 生成量的多样性，特别是 HAAs 和 HANs 的形成增加。在我们的毒性试验中，尽管 f>0.4 时拮抗作用占主导地位（f 指受影响的部分），但低浓度下的协同作用可以通过促进 N-DBPs 的生成来增强联合毒性。
