Analysis of water quality and detection of the agricultural glyphosate in sediments of the Ribeirão São João hydrographic basin in Porto Nacional- TO

Abstract

The Ribeirão São João hydrographic basin, located in the municipality of Porto Nacional - TO, is the main source of funding for urban supply. This main source has been suffering various aggressions, such as the exploitation of agriculture and livestock, where irrigation catchments are located. In this study, the water quality of Ribeirão São João was monitored. As it is a Class Two water resource of fresh water, it can be destined for supply for human consumption, swimming, irrigation of vegetables, parks, gardens, aquaculture and fishing. For the analysis of the Water Quality Index calculation of the State Environment Foundation (IQA-FEAM), nine parameters were weighted: pH, temperature, turbidity, total dissolved solids, dissolved oxygen, biochemical oxygen demand, total phosphorus, total nitrogen and thermotolerant coliforms and, the concentration of the pesticide glyphosate in the sediments of the reservoir. The results achieved showed that Ribeirão São João water can be classified as of medium quality with a value equal to 69, according to FEAM, even with some parameters in disagreement compared to environmental legislation with the standards determined by Resolution 357/2005 of the National Council Environment (CONAMA). As for the glyphosate concentration, the average obtained was 0.03 μg / L, lower than the limit value of 0.65 μg / L. The presence of the chemical substance probably came from the rains caused in this period under study.