Qualidade das águas superficiais e as atividades licenciadas potencialmente poluidoras no estado de Minas Gerais: estudo de caso das bacias hidrográficas do Rio das Velhas e do Rio Paraopeba

Abstract

Anthropogenic interference in water systems manifests itself in multiple dimensions, such as the discharge of industrial effluents, runoff from agricultural areas with agrochemicals, disorderly occupation of riverbanks, among others. For the management of human activities, environmental licensing is established by the National Environmental Policy as an instrument for its application, aiming at the management and regulation of human activities that impact water resources, establishing mechanisms for control and mitigation of possible environmental damages. The objective of this study was to analyze, in an integrated manner, the quality of surface waters in the Rio das Velhas and Paraopeba River Basins, investigating the possible correlation of the results with environmental licensing. The study methodology involved the analysis of water quality data collected between 2008 and 2023 at 66 monitoring stations in the Rio das Velhas River Basin and 30 stations in the Paraopeba River Basin. Forty physicochemical and microbiological parameters were evaluated, including fecal indicators, nutrients, metals, and other contaminants. Additionally, a survey of licensed activities in the river basins was conducted, considering the environmental licensing modalities established by state legislation. The characterization of environmental licenses issued by the state agency showed that, in both river basins, the issuance of environmental licenses for simplified environmental licensing was predominant, reaching 90% of the total licenses issued between 2018 and 2023. It was identified that the main activities in both river basins are from List F - Waste Management and Services, followed by List A - Mining Activities. Temporal analysis revealed seasonal variations in relation to the concentrations of water quality parameters, with nine parameters showing a higher percentage of stations with violations exceeding 50% of the samplings during the rainy season in the Rio das Velhas River Basin and seven in the Paraopeba River Basin. In the Rio das Velhas Basin, critical conditions were identified in the Mina stream, Onça creek, Arrudas creek, and Caeté stream, located in the Metropolitan Region of Belo Horizonte, where the main source of pollution was domestic and industrial effluents without proper treatment. In turn, in the Paraopeba River Basin, a concentration of high contamination levels was observed in urban and industrial areas, particularly in Betim, where stations BP071 (Betim River) and BP073 (Areias Creek) consistently showed high concentrations of multiple parameters, including fecal indicators, total phosphorus, nitrogen, and chloride. In both basins, a relationship was observed between licensed activities and water quality. Areas with a higher concentration of environmental licenses, especially for industrial and mining activities, tended to show higher levels of violation of established water quality standards.