Identificação e efeitos toxicológicos dos subprodutos gerados na degradação de microcistina-LR por processos oxidativos avançados

Abstract

Among the harmful effects caused by the process of eutrophication of natural waters, an important highlight should be given to the appearance of cyanobacterial blooms and the consequent generation of cyanotoxins with a potent hepatotoxic effect (eg microcystin-LR). The presence of strains of cyanobacteria that produce cyanotoxins has negative effects on water bodies and in particular those destined for public supply, due to the harmful effect of these substances on human and animal health. Conventional water treatments are inefficient for the total removal of these toxins, so new alternative technologies are needed, such as advanced oxidative processes. However, these technologies favor the formation of unknown by-products. The present work sought to evaluate the toxicological effects of possible by-products formed from the degradation of Microcystin-LR by advanced oxidative processes. Data from 4 case studies were used that used two advanced oxidative processes: UV / H2O2 and Fenton, to obtain the obtained m / z ion fragments. The case studies used water contaminated with Microcystin LR in different concentrations. Sample analysis was performed using high performance liquid chromatography coupled to mass spectrometry (HPLC-EM). The ChemDraw and ChemSketch software were used to form the structures and chemical formulas for each fragment. The Pubchem, Echa, Ecotox, TSCA and MolBase databases were used to identify the toxicology of the fragments. 33 fragments identified in the 4 case studies were obtained. The first by-products identified showed an intact cyclic molecular structure and during the course of the degradation they were linearized. The fragments of m / z 967 and 553 had toxicity registered by the databases. The UV / H2O2 treatment generated toxic by-products and large molecules. The treatment using Fenton presented the best performance, being indicated for the treatment of Microcystin-LR in water destined for supply.