Avaliação e índice de qualidade da água: análise de agrotóxicos por cromatografia em fase gasosa acoplada à espectrometria de massas na bacia do rio do campo, município de Campo Mourão - PR

Abstract

Rio do Campo is the source of water abstraction responsible for 80% of the public supply of Campo Mourão-PR. The study area comprises approximately 170 km², the use of the soil is predominated by agriculture in the surroundings of the Rio do Campo basin, in the areas of springs at points 01, 02, 03 upstream of the catchment point for public supply and the urban perimeter; agriculture, being cultivars soybean, maize and wheat, in points 04, 05, 06, bordering the urban perimeter of the municipality of Campo Mourão-PR. The objective of this research was to evaluate the water quality, through the physical-chemical and biological parameters for Temperature, Potential of hydrogen, Oxidation Potential, Conductivity, Dissolved Oxygen, Dissolved Oxygen Percentage, Total Residue, Fecal Coliforms, Biochemical Oxygen Demand, Total Nitrogen, Total Phosphorus, as well as the analysis of agrochemicals by gas chromatography coupled to mass spectrometry. Five samples of water were collected, in the period from March 2016 to May 2017, three samples upstream from the catchment for supply, and another three downstream from the catchment. The results obtained for the water quality index (WQI) for points 03 and 06 were compared with those of the resolution of the National Environmental Council (CONAMA) nº 357/2005 and classification by the National Water Agency (ANA), of these physical-chemical and biological analyzes. For the BDO, total nitrogen and phosphorus analyzes at collection point 03, the results are 2.0 mg L-1, 4.25 mg L-1 and 4.25 mg L-1, respectively, and at point 06 were 22.4 mg L-1, 4.25 mg L-1 and 0.10 mg L-1, these results showed a change compared to the current legislation, in which nitrogen was 13% above the maximum allowed value and phosphorus 45 times higher and classified in the water quality index as terrible. In the coliform analysis, the result showed the presence of thermotolerant coliforms in amounts exceeding the limit of 1000 coliforms / 100 ml, also classified in the water quality index as terrible. The water quality index - WQI calculated was 41 and classified as bad, the raw water of Rio do Campo between collecting points 03 and 06, and the trophic status index for total phosphorus - TSI(TP) pointed to the classification as mesotrophic, with intermediate productivity and possible implications on water quality, but at acceptable levels. The analysis for identification of pesticides by gas chromatography coupled to mass spectrometry (GC/MS) in the samples showed the presence of these analytes in 16 samples of the 30 analyzed. Of the 21 pesticides studied, 9 were detected and 7 quantified. The concentration values of the pesticides in the samples ranged from 1.9 to 153 ng L-1. The pesticides identified in the samples are: Heptachlor, Heptachlor epoxide, Aldrin, Endrin, Dieldrin, Endosulfan, Metolachlor, Permethrin and DDT. The (CG / MS) method applied in this work allowed the determination of organochlorine pesticides in water samples. The limits found were low, sufficient to detect these substances at a level lower than that established by national legislation. These results allow us to conclude that organochlorine pesticides are still being used in large quantities and are used as a tool to increase agricultural production. The data also demonstrate the constant need to monitor water quality in supply sources.