Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States.
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Beijing 100085, People's Republic of China.
Environ Sci Technol. 2023 Nov 28;57(47):18788-18800. doi: 10.1021/acs.est.3c00771. Epub 2023 Jul 7.
As disinfection byproducts (DBPs) are ubiquitous sources of chemical exposure in disinfected drinking water, identifying unknown DBPs, especially unknown drivers of toxicity, is one of the major challenges in the safe supply of drinking water. While >700 low-molecular-weight DBPs have been identified, the molecular composition of high-molecular-weight DBPs remains poorly understood. Moreover, due to the absence of chemical standards for most DBPs, it is difficult to assess toxicity contributions for new DBPs identified. Based on effect-directed analysis, this study combined predictive cytotoxicity and quantitative genotoxicity analyses and Fourier transform ion cyclotron resonance mass spectrometry (21 T FT-ICR-MS) identification to resolve molecular weight fractions that induce toxicity in chloraminated and chlorinated drinking waters, along with the molecular composition of these DBP drivers. Fractionation using ultrafiltration membranes allowed the investigation of <1 kD, 1-3 kD, 3-5 kD, and >5 kD molecular weight fractions. Thiol reactivity based predictive cytotoxicity and single-cell gel electrophoresis based genotoxicity assays revealed that the <1 kD fraction for both chloraminated and chlorinated waters exhibited the highest levels of predictive cytotoxicity and direct genotoxicity. The <1 kD target fraction was used for subsequent molecular composition identification. Ultrahigh-resolution MS identified singly charged species (as evidenced by the 1 Da spacing in C isotopologues), including 3599 chlorine-containing DBPs in the <1 kD fraction with the empirical formulas CHOCl, CHOCl, and CHOCl, with a relative abundance order of CHOCl > CHOCl ≫ CHOCl. Interestingly, more high-molecular-weight CHOCl DBPs were identified in the chloraminated vs chlorinated waters. This may be due to slower reactions of NHCl. Most of the DBPs formed in chloraminated waters were composed of high-molecular-weight Cl-DBPs (up to 1 kD) rather than known low-molecular-weight DBPs. Moreover, with the increase of chlorine number in the high-molecular-weight DBPs detected, the O/C ratio exhibited an increasing trend, while the modified aromaticity index (AI) showed an opposite trend. In drinking water treatment processes, the removal of natural organic matter fractions with high O/C ratio and high AI value should be strengthened to minimize the formation of known and unknown DBPs.
作为消毒副产物 (DBPs) 是消毒饮用水中化学暴露的普遍来源，识别未知的 DBPs，尤其是未知的毒性驱动因素，是饮用水安全供应的主要挑战之一。虽然已经鉴定出超过 700 种低分子量 DBPs，但对高分子量 DBPs 的分子组成仍了解甚少。此外，由于大多数 DBPs 缺乏化学标准，因此难以评估新鉴定的 DBPs 的毒性贡献。基于效应导向分析，本研究结合预测细胞毒性和定量遗传毒性分析以及傅里叶变换离子回旋共振质谱 (21 T FT-ICR-MS) 鉴定，以确定在氯胺化和氯化饮用水中诱导毒性的分子量分数，以及这些 DBP 驱动因素的分子组成。超滤膜的分级允许研究 <1 kD、1-3 kD、3-5 kD 和 >5 kD 分子量分数。基于硫醇反应的预测细胞毒性和单细胞凝胶电泳的遗传毒性检测表明，氯胺化和氯化水的 <1 kD 分数均表现出最高水平的预测细胞毒性和直接遗传毒性。<1 kD 的目标分数用于后续的分子组成鉴定。超高分辨率 MS 鉴定出单价物种（证据是 C 同量异位素中 1 Da 的间隔），<1 kD 分数中包含 3599 种含氯 DBPs，经验公式为 CHOCl、CHOCl 和 CHOCl，相对丰度顺序为 CHOCl > CHOCl ≫ CHOCl。有趣的是，在氯胺化水中鉴定出的高分子量 CHOCl DBPs 比氯化水中更多。这可能是由于 NHCl 的反应较慢。氯胺化水中形成的大多数 DBPs 由高分子量 Cl-DBPs（高达 1 kD）组成，而不是已知的低分子量 DBPs。此外，随着检测到的高分子量 DBPs 中氯原子数量的增加，O/C 比呈上升趋势，而改良芳香性指数 (AI) 呈相反趋势。在饮用水处理过程中，应加强去除具有高 O/C 比和高 AI 值的天然有机物分数，以最大限度地减少已知和未知 DBPs 的形成。
