Qualidade das águas fluviais em área sob influência direta da mineração de calcário em Caçapava do Sul – RS: período de 2007-2016

Abstract

The municipality of Caçapava do Sul is the largest producer of dolomitic limestone in the state of Rio Grande do Sul, with mining being one of the main bases of its economy. Among the impacts arising from this activity is the interference in water resources, so the monitoring of water is an important tool for environmental management and control. Thus, the present study aimed to diagnose the quality of the surface waters located in the limestone mining area. Ten monitoring points located in the Mangrove, Salso and Irapuazinho Rivers were evaluated during ten years, in the period 2007 to 2016. From these points, taking into account the water flow of the studied water bodies, four precede the mining, eight cover the mining area and one of them is located after the activity. The following physicochemical parameters were evaluated: alkalinity, organic carbon, conductivity, BOD5, COD, phosphorus, nitrate, dissolved oxygen, pH and total solids, after which the results were compared with CONAMA Resolution 357/2005 to identify their respective classifications. The analysis of the mean for each parameter over the years has demonstrated all within the established limits. When evaluated individually, Arroio Irapuazinho, where the only point that after mining was located, was classified as class 1 in nine of the ten years of study, except for the year of 2012 where the pH parameter was 0.34 above tolerated limit. By determining the Pearson Linear Correlation Coefficient between rainfall and the parameters studied, there was a strong positive correlation with the organic carbon and a strong negative correlation with the parameters alkalinity, conductivity and nitrate. Among the analyzed parameters, alkalinity, conductivity, total solids and pH were the ones that showed the greatest relation with the development of the mining activity.