Calibration of a groundwater quality index (IQNAS) for the region of vale do Rio Pardo, RS, Brazil: new technological tool for environmen-tal monitoring

Abstract

This study aimed to calibrate a groundwater quality index for the region of Vale do Rio Pardo, RS, Brazil, in order to evaluate the water quality, through physical, chemical and microbiological analysis, in two sampling campaigns, developed in the period from February to September 2015. The parameters analyzed were benzene, total coliform, Escherichia coli, iron, manganese, chloride, fluoride, hardness, pH, sulfates, turbidity, nitrate, ammonia nitrogen, total mercury, electrical conductivity, Total Dissolved Solids, alkalinity (carbonates, bicarbonates and hydroxides), sodium and potassium. Based on the main published indices of groundwater quality (SEQ- EAUX Souterraines, Deininger, IQNAS, IQASB), and considering the chemical typology of the region (excessive fluoride ions in 18% of samples), the IQNAS was chosen because reflects in a more representative way the quality of these waters. To calibrate the weights of the variables used for the IQNAS calculation, the choice was the Principal Component Analysis. Considering the priority uses of groundwater in the region, the parameters chloride and fluoride were identified as the most important variables with the biggest weight for index formulation. In this way, by applying the calibrated IQNAS, 74% of water samples showed the best quality, 9% good quality and 17% are improper for human consumption. In conclusion, the calibrated IQNAS in this work is an efficient tool to represent the environmental conditions in the region.

Keywords

• Água subterrânea. Índice de qualidade da água. Fluoreto. Vale do Rio Pardo, RS.