Estudo de risco de contaminação em reservatórios de usinas hidrelétricas no estado de Goiás: análise por geoprocessamento e desenvolvimento de metodologia analítica de poluentes em água

Abstract

Organic and inorganic compounds, when above the limits imposed by legislation, compromise the quality of water in water bodies and become pollutants that can cause varied impacts. Especially in Hydroelectric Power Plants (HPP) reservoirs, where may occur secondary activities such as irrigation, fishing, leisure, supplying cities, etc. Therefore, the objective of this work was to identify reservoir areas in the state of Goiás at potential risk of water contamination and develop a methodology to detect and quantify pollutants present in water, focusing on research on some substances defined by Brazilian legislation. To identify potential risk areas, a geoprocessing software was used, combined with the IBGE and SIEG databases and the MapBiomas project's land use and land cover database. For detection and quantification of pollutants, extraction and pre-concentration of solid phase analytes (SPE) were used, followed by analysis in an X-Ray Fluorescence (FRX) spectrometer and by statistical and multivariate treatment of scattering and fluorescence data. For solid phase extraction were used corn cob vegetable fiber and Amberlite IR-120® cation exchange resin. Both materials were treated with acid and with base, were subjected to characterization analyzes and compared with commercial SPE cartridges. In four reservoirs in the state of Goiás, potential risks of water contamination by pesticide residues from pasture, soy and sugarcane were identified. In two reservoirs, the risks of water contamination by metals from mining activities were identified. The analysis of the water collected in these reservoirs showed that iron exceeded the water potability limit of 0.3mg/L in the four analyzed HPPs, in addition to aluminum above 0.2mg/L in the Itumbiara HPP. The results reinforce the importance of monitoring. The characterization showed the effects of treatments with acid and base, giving the vegetable fiber and cationic resin desirable attributes to improve the adsorption capacity. The PLS model used in the multivariate calibration, after extraction in vegetable fiber from acid-treated corn cob, showed good results for diuron and glyphosate in # 100 Mesh fiber. In the univariate calibration, applied to metals dissolved in water after SPE extraction, the reduction of the vegetable fiber granulometry and a greater volume of solution were important to obtain good results for Fe, Cu and Zn adsorbed on fiber and resin treated with base as well. as in the cationic SPE cartridge. Tests showed the X-ray stability of the adsorbent materials, for 10 consecutive analyzes and for up to 60 days. The calculated limit of quantification (LQ) for glyphosate in acid treated fiber was 0.134mg/L, and for Fe, Cu and Zn in base treated fiber was 0.199, 0.122 and 0.157mg/L respectively. The LQ show that the SPE and FRX methodology meet the maximum limits allowed in the Brazilian legislation for water potability and for the classification of natural waters, except for copper that did not comply with CONAMA Resolution 357.