Avaliação do potencial efeito tóxico de cianotoxinas e seus subprodutos de degradação por processos oxidativos avançados

Abstract

Cyanobacteria are distributed throughout the world and their blooms are a concern in aquatic ecosystems since they reduce water quality and the efficiency of energy flow from producers to consumers, as they have low nutritional value and generate cyanotoxins. The application of associated and/or complementary treatments can be a solution in the reduction or elimination of these microorganisms. In this case, advanced oxidative processes (AOP's) constitute a special class of oxidation techniques indicated as favorable, producing hydroxyl free radicals (OH.), which are traditionally considered as active species, responsible for the rapid reaction of several organic molecules, however, they present application restrictions in conditions of high concentration of pollutants and there is formation of reaction by-products, which in some cases are toxic. In this context, this research aimed to identify, quantify and evaluate the potential toxic effect of cyanotoxins and by-products formed from the degradation of microcystin-LR by Fenton's advanced oxidative process. Therefore, the research was divided into five stages. At first, we sought to understand the state of the art of research related to the topic, starting from a descriptive analysis, with subsequent in-depth analysis of current studies, described in chapter 1. Chapter 2 and 3 describe the chronic and acute effects of cyanotoxins (MCLR, SXT, ATX-A and CYN) using Chlorella vulgaris and Daphnia magna as test organisms, respectively. The efficiency of the advanced oxidative process (Fenton) in the degradation of microcystin-LR and its by-products were evaluated by computational molecular modeling, mass spectrometry and in vivo tests with Chlorella vulgaris and Daphnia magna and are presented in chapter 4. Finally, the fifth and last chapter presents the phytotoxicity of lysed extracts of cyanotoxins on germination, hypocotyl growth, root elongation and initial development of seedlings of lettuce seeds (Lactuca sativa L.), as well as evaluation of the MC-LR by-products obtained after the Fenton oxidative process. The study of toxicological and oxidation treatment promoted the determination of deleterious effects of these organic micropollutants, allowing the verification of ecotoxicological characteristics, mechanisms of action on living organisms and definition of guidelines for quality control of eutrophic effluents