Vulnerabilidade à poluição das águas subterrâneas Um estudo do Aquífero Bauru na zona urbana de Araguari, MG

Abstract

This work deals with the main aspects related to the study of the vulnerability intrinsic to the pollution of the aquifer Bauru placed under the urban zone of Araguari, MG. The analysis applied the GOD Method and put forward new parameters in order to get a broader evaluation (Hybrid Method). By this way, the main parameters considered in the study of vulnerability were the water table depth, the variety of soil that constitutes the surface, the vertical hydraulic conductivity of the surface, groundwater occurrence and ground slope. The research includes field data collecting, laboratory analyses and computational tasks, such as interposing spatial data and drawing maps. By monthly observing 31 wells from the aquifer Bauru, it can be noticed that the aquifer is not deep: 9,67% of all wells are less than 10 meters low; 51,61% are between 10 and 30 meters low; and 38,71% are more than 30 meters low. According to the assessments, the aquifer Bauru is exposed to a potential water pollution risk in urban zone. The hydraulic conductivity, also considered in the vulnerability evaluation, indicated that, in general, Araguari superficial soil allows the water penetration (its average value is 1.92x10-2cm/s). Comparing GOD, Hybrid and EKv Methods, the difference in the final vulnerability indices is noticeable. According to the GOD Method, the final indices were set between low and medium levels. On the other hand, according to the Hybrid Method, these final indices were set between high and very high levels. The water quality was tested in order to provide a better description of the aquifer. Such analysis, according to temporal and spatial parameters, indicated that the water table shows low rates of total and fecal coliform bacteria. The DBO5 exams indicated high concentrations and in 60% of all analyses the results were above the 5.0 mgO2/L recommended by the CONAMA Resolution 357: 2005. Otherwise, chemical analyses pointed out that nitrate concentrations were under the 10 mg/L recommended by M.S. Decree 518: 2004.