Amostragem instantânea e passiva na análise de pesticidas em água de nascente do Alto Rio São Lourenço em Campo Verde - MT

Abstract

São Lourenço River has its headwaters in the municipality of Campo Verde - MT and runs through the states of Mato Grosso and Mato Grosso do Sul, discharging in the Pantanal region. The study area suffers direct impact of increased agricultural activity and previous studies have shown the presence of pesticides in their water bodies. Considering the impacts caused by these compounds in the environment the objective of this study was to evaluate the recovery process performed in one of the headwaters of the São Lourenço River and its effect on water contamination by pesticides and test in exploratory and unprecedented nature in the state the use of passive sampling for water analysis. Therefore, grab water samples were collected during the dry and rainy season, starting in December 2015 and followed until the end of the harvest season (June 2016), where soy bean, corn and cotton were cultivated. Passive samplers were also used to collect integrative samples and analyzes were carried out using extraction methods developed and validated for Biocidal Residue Analysis Laboratory UFMT. The identification and quantification were made by gas chromatograph coupled with mass detection (GC/MS) for atrazine, malathion, trifluralin, metribuzin, lambda cyhalothrin, permethrin, metolachlor, chlorpyrifos, endosulfan α, β and sulfate. The pesticides carbendazim, carbofuran, carbosulfan, acetamiprid, thiamethoxam, pyraclostrobin, diuron, clomazone, epoxiconazole, imidacloprid, methomyl and tebuconazole were analyzed by liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). A total of 95 water samples were collected, 56 of groundwater and 39 of surface water. Of these, 61% and 41%, respectively, showed pesticide residues. Eight active ingredients were detected in groundwater and 11 in surface water, showing the vulnerability of the area to contamination. The atrazine herbicide and the fungicide pyraclostrobin were detected only with the use of passive sampler demonstrating the relevance and usefulness of this strategy in the sample measurement of low concentrations of pesticides. Metolachlor, atrazine, malathion and trifluralin had been previously detected, proving the great potential of contamination of these pesticides either by runoff, leaching or other means. Among these, trifluralin and malathion showed concentrations above the permitted by Brazilian legislation for pesticide residues in water matrices. Regarding the effect of vegetation recovery on the waters contamination, a significant improvement in retention of pesticides was observed, since the concentrations found were lower than those reported in previous studies. However, future monitoring will be important to assess the future effects, since the recovery process consolidates in the long term.