Ultraviolet photosensitized transformation mechanism of microcystin-LR by natural organic matter in raw water

Sun, Qiyuan; Zhang, Tianfang; Wang, Feifeng; Liu, Changqing; Wu, Chunshan; Xie, Rongrong; Zheng, Yanmei

doi:10.1016/j.chemosphere.2018.06.091

Cited by 13 publications

(2 citation statements)

References 50 publications

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“…One organic compound with natural photosensitizing properties is fulvic acid (FA). The photodegradation of MC-LR by FA apparently follows second-order reaction kinetics and is highly dependent on pH [32]. In another study, humic acid and suspended solids collected from natural samples showed to affect the photo-degradation of dissolved MC-LR [33].…”

Section: Microcystin-lr Decompositionmentioning

confidence: 92%

Environmentally Friendly and Cost-Effective Approaches to Reduce Toxin Content in Toxic Cyanobacterial Biomasses

Loss,

Azevedo,

Azevedo

et al. 2024

Biomass

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Cyanobacterial outgrowths are naturally occurring processes in eutrophic aquatic ecosystems. Furthermore, as a result of climate change and anthropogenic pollution, cyanobacteria harmful algal blooms (CyanoHABs) are expanding worldwide. CyanoHABs are considered a threat to human health and environment due to the production of potent toxic substances, but at the same time, valuable products can be obtained from these microorganisms. The main objective of this study was to test straightforward and cost-effective methods to reduce the toxin content of cyanobacterial biomass for the exploitation of this important biological resource. To carry out this study, lyophilized or hydrated biomass from microcystin-LR (MC-LR) producing Microcystis aeruginosa and cylindrospermopsin (CYN) producing Chrysosporum ovalisporum strains were subjected to the following treatments: (1) thermal (50 °C); (2) ultraviolet (UV) radiation; (3) ozone; and (4) sunlight, for periods varying between 2 and 12 h. MC-LR and CYN concentrations were quantified by LC-MS and compared between experimental groups. The results show a significant reduction in the amount of MC-LR in M. aeruginosa biomass (lyophilized and hydrated) exposed to sunlight. Since no other treatment reduced MC-LR in M. aeruginosa biomass, this molecule was demonstrated to be very stable. Regarding CYN, the concentration of this toxin in C. ovalisporum biomass was significantly reduced with the exposure to UV radiation, to approximately 51% of the initial concentration after 2 h of exposure; 86% reduction after 5 h of exposure; and 77% reduction after 12 h of exposure. Overall, this study demonstrates that the toxicity of cyanobacterial biomass can be reduced by employing environmentally friendly and cost-effective treatments with sunlight and UV radiation.

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Section: Microcystin-lr Decompositionmentioning

confidence: 92%

Environmentally Friendly and Cost-Effective Approaches to Reduce Toxin Content in Toxic Cyanobacterial Biomasses

Loss,

Azevedo,

Azevedo

et al. 2024

Biomass

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“…Organic matter in surface waters can act as photosensitizers when they absorb sunlight to form a triplet excited state molecule and subsequently produce other reactive species [32]. In the presence of pigments or dissolved organic matter, photosensitized reactions appear to play an important role in the environmental transformation of microcystins, including reactions with hydroxyl radicals and triplet state excited molecules [33][34][35]. Thus far, studies mostly focused on the fate of four microcystin variants (MC-LR, MC-RR, MC-YR, MC-LA), while 279 microcystins are known to date [36].…”

Section: Introductionmentioning

confidence: 99%

Phototransformation kinetics of cyanobacterial toxins and secondary metabolites in surface waters

2021

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Background Cyanobacteria and their toxins occur in high concentrations during the so-called bloom events in surface waters. To be able to assess the risks associated with cyanobacterial blooms, we need to understand the persistence and fate processes of these toxins and other bioactive metabolites. In this study, we investigated the photochemical fate of 54 cyanopeptides extracted from two strains of Microcystis aeruginosa (PCC7806 and UV006), Planktothrix rubescens, and Dolichospermum flos aquae. We determined half-lives during sunlight exposure in lake water and inspected the effect of pH on transformation kinetics for 27 microcystins, 8 anabaenopeptins, 14 cyanopeptolins, 2 cyclamides, and 3 aeruginosins. Results For cyanopeptides from D. flos aquae and P. rubescens, we observed the highest removal of 28 and 26%, respectively, after 3-h sunlight exposure. Most cyanopeptides produced by the two M. aeruginosa strains were rather persistent with only up to 3% removal. The more reactive cyanopeptides contained amino acids known to undergo phototransformation, including methionine and tyrosine moieties or their derivatives. Photochemical half-lives of 14 tyrosine-containing cyanopeptides decreased by one order of magnitude from nearly persistent conditions at pH 7 (half-life > 70 h) to shorter half-lives at pH 10 (< 10 h). Conclusions More work is needed to distinguish the contribution of different photochemical reaction pathways including the contributions to the pH effect. To the best of our knowledge, this is the first assessment of transformation kinetics of such a wide range of cyanopeptides. The abundant and persistent cyanopeptides that have not been studied in detail yet should be prioritized for the evaluation of their ecosystem and human health risks and for their abatement during drinking water treatment.

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Synergistic microcystin degradation by a novel bacterium isolated from shrimp pond and fulvic acids

Qin,

Dai,

et al. 2024

J. Ocean. Limnol.

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Ultraviolet photosensitized transformation mechanism of microcystin-LR by natural organic matter in raw water

Cited by 13 publications

References 50 publications

Environmentally Friendly and Cost-Effective Approaches to Reduce Toxin Content in Toxic Cyanobacterial Biomasses

Environmentally Friendly and Cost-Effective Approaches to Reduce Toxin Content in Toxic Cyanobacterial Biomasses

Phototransformation kinetics of cyanobacterial toxins and secondary metabolites in surface waters

Synergistic microcystin degradation by a novel bacterium isolated from shrimp pond and fulvic acids

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