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Chlorination of microcystin-LR in natural water: Kinetics, transformation products, and genotoxicity.
- Source :
-
Journal of Environmental Management . Jul2023, Vol. 338, pN.PAG-N.PAG. 1p. - Publication Year :
- 2023
-
Abstract
- 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−1 - 8.0 mg L−1), the apparent second-order rate constants for MC-LR chlorination varied from 21.3 M−1s−1 to 31.9 M−1s−1 in MQ, higher than that in LLW (9.06 M−1s−1 to 17.7 M−1s−1) 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. [Display omitted] • Removal rate of MC-LR via chlorination in natural water, decreased due to water matrix. • Degradation products of MC-LR by chlorine were identified. • There was no genotoxicity for MC-LR degradation after chlorination based on Ames assay. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 03014797
- Volume :
- 338
- Database :
- Academic Search Index
- Journal :
- Journal of Environmental Management
- Publication Type :
- Academic Journal
- Accession number :
- 163118062
- Full Text :
- https://doi.org/10.1016/j.jenvman.2023.117774