Caracterização hidroquímica de águas superficiais em área utilizada para cultivo de soja no município de Caçapava do Sul/RS

Abstract

The quality and availability of surface water are of utmost importance for the development of modern society. This work aims to characterize hydroquimically a dam and a cacimba well in a rural property in the interior of Caçapava do Sul and determine the physical and chemical characteristics of these waters by analyzing possible contamination by agricultural pesticides used in soybean cultivation. In the physical-chemical parameter, pH, alkalinity, hardness, conductivity, chlorides, turbidity were evaluated. The search for metals in the waters was determined by x-ray fluorescence and the presence of glyphosate herbicide was identified through the direct injection method in an ultra-efficient liquid chromatography system coupled to sequential mass spectrometry. In the physical-chemical parameter, all indices remained within the standards adopted by CONAMA legislation 357/2005, with the exception of the cacimba well that maintained an average pH of 5.7, slightly below 6.0, minimum required. X-ray fluorescence determined the presence of cadmium, a heavy metal that causes many diseases. As the method determines qualitatively and not quantitatively it is not possible to analyze whether it is in conformity with the resolutions of the National Council of the Environment. The presence of the glyphosate herbicide showed that the concentration of 7 μg / L is well below that accepted for class 1 waters according to CONAMA, which is 65 μg / L. Despite the fact that the surrounding area does not have native vegetation and riparian forests and intense plantation of soybean crops, these factors alone have not yet been enough to definitively alter water quality, at least in the physical-chemical parameters evaluated in this study.