Avaliação da biodegradabilidade e toxicidade de fluidos dielétricos de transformadores em solo e meio aquático

Abstract

Power distribution companies constantly contaminate the environment with dielectric fluids due to power transformer failures and leaks. In this way, these fluids should be studied, as they may entail the vulnerability of the fauna and flora. In this sense, the objective of this work was to investigate the deleterious effects of vegetal and mineral dielectric fluids, through biodegradability, acute toxicity, chemical attributes and soil degradation (oils and greases) tests as well as soybean phytotechnical characteristics evaluation. In the tests of the immediate biodegradability, vegetal dielectric fluids of crambe, W3, W6 and W9 and one based on mineral oil (Lubrax) were studied. For the acute toxicity tests with Danio rerio and Artemia salina and the soil toxicity tests using soybean (Glycine max L.), the W3 and Lubrax dielectric fluid were used. The biodegradability analysis was evaluated by the action of microorganisms that transformed the sample into CO2, being measured by titulometry. For the acute toxicity studies, two distinct experiments were performed, where the organisms were exposed to different concentrations of the W3 and Lubrax dielectric fluids and to the FSA of the fluids. The FSA of W3 and Lubrax used in the Danio rerio assay were subjected to gas chromatography analysis. The acute toxicity tests with Danio rerio and Artemia salina were carried out in order to know the approximate range of fluid toxicity, taking into account the lower dilution that caused lethality in 50% of organisms (LC50). The soil chemical attributes analyzed were: pH, P, K, Ca, Mg, CTC and V. The content of oils and greases of the dielectric fluids was quantified by the Soxhlet type extraction method. For the phytothecnical evaluations, emergence, plant height, stem diameter, root length, root dry matter, number of pods and grains, and the mass of one thousand grains were analyzed. Vegetable dielectric fluids are biodegradable over a period of 14 days, while mineral oil is difficult to biodegrade. In the acute toxicity study, W3 had a lower LC50 than Lubrax, causing higher mortality in the organisms. The LC50 for the Danio rerio was 2.46 gL-1 (Lubrax) and 0.318 gL-1 (W3). For Artemia salina the LC50 was 4.63 gL-1 (Lubrax) and 0.641 gL-1 (W3). In relation to the FSA tests, the Lubrax one caused a greater toxic effect on the organisms, while the W3 had no toxic effect on 50% of organisms. The LC50 values for Lubrax were 4.89% for the Danio rerio and 7.67% for Artemia salina. Chromatographic analysis of FSA of the fluids was not conclusive, it only suggests that the toxicity may be related to the solubility of all the substances present in Lubrax and not only to the solubility of n-alkanes. The chemical attributes of the soil did not change significantly, only the carbon presented increasing variation in relation to the concentrations of the fluids. There was a reduction of the TOG during the agricultural years and the soils in the presence of W3 presented greater degradation than those with Lubrax. The increase in the concentration of the dielectric fluids caused a reduction in the phytotechnical characteristics of the soybean. Plants from soil contaminated with W3 showed better development compared to plants that were in soil contaminated with Lubrax.