Ultrasonically Induced Degradation of Microcystin-LR and -RR: Identification of Products, Effect of pH, Formation and Destruction of Peroxides
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- 作者：Weihua Song ; Armah A. de la Cruz ; Kathleen Rein ; and Kevin E.O'Shea
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：June 15, 2006
- 年：2006
- 卷：40
- 期：12
- 页码：3941 - 3946
- 全文大小：172K
- 年卷期：v.40,no.12(June 15, 2006)
- ISSN：1520-5851
文摘
Microcystins (MCs) are a family of toxic peptides producedby a number of cyanobacteria commonly found in lakes,water reservoirs, and recreational facilities. The increasedeutrophication of freshwater supplies has led to anincrease in the incidence of cyanobacterial harmful algalblooms and concerns over the public health implicationsof these toxins in the water supply. Conventional watertreatment methods are ineffective at removing lowconcentrations of cyanotoxins, hence specialized treatmentis usually recommended for treatment of contaminatedwater. In this study, the products of ultrasonically induceddegradation of microcystin-LR (MC-LR) and microcystin-RR (MC-RR) were analyzed by LC-MS to elucidatethe probable pathways of degradation of these toxins.Results indicate preliminary products of sonolysis of MCsare due to the hydroxyl radical attack on the benzenering and diene of the Adda peptide residue and cleavageof the Mdha-Ala peptide bond. The effect of pH on thetoxin degradation was evaluated since the pH of the solutionchanges upon ultrasonic irradiation and varies with thewater quality of treatable waters. The initial rate ofMC-LR degradation is greater at acidic pH and coincideswith the change in hydrophobic character of MC-LR asa function of pH. Hydrogen and organic peroxides are formedduring ultrasonic irradiation, but can be eliminated byadding Fe(II). The addition of Fe(II) also accelerates thedegradation of MC-LR, presumably by promoting the formationof hydroxyl radicals via conversion of ultrasonicallyproduced H2O2. These findings suggest that sonolysis caneffectively degrade MCs in drinking water.