CAS Key Laboratory of Urban Pollutant Conversion, Fujian Key Laboratory of Watershed Ecology, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
CAS Key Laboratory of Urban Pollutant Conversion, Fujian Key Laboratory of Watershed Ecology, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China.
J Environ Manage. 2023 Jul 15;338:117774. doi: 10.1016/j.jenvman.2023.117774. Epub 2023 Mar 28.
Microcystin-LR (MC-LR), a type of cyanotoxin commonly found in natural water bodies (sources of drinking water), poses a threat to human health due to its high toxicity. It is essential to successfully remove this cyanotoxin from drinking water sources. In this study, chlorine was used to oxidize MC-LR in Milli-Q water (MQ) (control test) and natural water collected from Lake Longhu (LLW) as a drinking water source. The removal efficiency, proposed transformation pathways, and genotoxicity were investigated. In the chlorine dose range investigated (4.0 mg L - 8.0 mg L), the apparent second-order rate constants for MC-LR chlorination varied from 21.3 Ms to 31.9 Ms in MQ, higher than that in LLW (9.06 Ms to 17.7 Ms) due to a faster chlorine decay attributed to the water matrix (e.g., natural organic matter) of LLW. Eleven transformation products (TPs) of MC-LR were identified in the two waters. The conjugated diene moieties and benzene ring of Adda moiety (3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid), and the double bond of Mdha moiety (N-methyldehydroalanine) were the major susceptible reaction sites. Attacking unsaturated bonds by hydroxyl and chlorine radicals to generate monochloro-hydroxy-MC-LR was the primary initial transformation pathway, followed by nucleophilic substitution, dehydration, and cleavage in MC-LR. Chlorine substitution on the benzene ring was also observed. Based on the bacterial reverse-mutation assay (Ames assay), TPs in treated natural water did not induce genotoxicity/mutagenicity. These findings shed light on the role of chlorination in controlling the risk of cyanotoxins in drinking water treatment plants.
微囊藻毒素-LR（MC-LR）是一种常见于天然水体（饮用水源）的蓝藻毒素，由于其高毒性对人类健康构成威胁。因此，必须成功地从饮用水源中去除这种蓝藻毒素。本研究采用氯氧化法处理 Milli-Q 水（MQ，对照实验）和取自龙湖水（LLW）的天然水（作为饮用水源）中的 MC-LR。考察了去除效率、提出的转化途径和遗传毒性。在所研究的氯剂量范围内（4.0 mg L -1 至 8.0 mg L -1），在 MQ 中，MC-LR 的表观二级氯化速率常数为 21.3 Ms 至 31.9 Ms，高于 LLW 中的速率常数（9.06 Ms 至 17.7 Ms），这是由于 LLW 中的水基质（如天然有机物）导致氯衰减更快。在两种水中均鉴定出 11 种 MC-LR 的转化产物（TPs）。Adda 部分（3-氨基-9-甲氧基-2,6,8-三甲基-10-苯代癸-4,6-二烯酸）的共轭二烯部分和苯环以及 Mdha 部分（N-甲基脱氢丙氨酸）的双键是主要的易反应位点。羟基和氯自由基攻击不饱和键，生成单氯-羟基-MC-LR，是初始转化途径，随后是 MC-LR 中的亲核取代、脱水和裂解。也观察到苯环上的氯取代。基于细菌回复突变试验（Ames 试验），处理后的天然水中的 TPs 未诱导遗传毒性/致突变性。这些发现阐明了氯化作用在控制饮用水处理厂中蓝藻毒素风险方面的作用。
