A new groundwater quality index for hydrogeological assessment in mining regions

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ABSTRACT Graphical abstract showing groundwater monitoring in Minas Gerais. Left: map with monitoring sites Norte de Minas, Rio das Velhas, PAN, and Guarani. Bottom: dataset of 124 wells, 795 samples from 2018–2022, and 10 parameters. Right: methodology using an equation to calculate water quality index classified as excellent, good, fair, poor, or very poor. The work proposes a groundwater quality index (GQI) for use in areas with mining potential, based on data collected from 2018 to 2022 in four monitoring networks comprising 124 wells in the Southeast Region of Brazil. The wells were classified using the new index and compared with classifications obtained through the WQICCME index, which offers flexibility in selecting parameters, matrices and reference values. Cluster analysis and principal component analysis (PCA) were also performed. The GQI was developed using parameters – As, Pb, Hg, nitrate, U, hardness, Fe, Mn and Zn – commonly associated with the dissolution of geological materials. Curves were constructed, weights assigned and wells subsequently classified according to both GQI and WQICCME. From a dataset of 795 records, GQI results were generally more conservative, attributed to the weighting scheme employed. Despite limitations, the cluster analysis showed stronger agreement with classifications derived from the GQI than from the WQICCME. PCA identified five principal components explaining 79.9% of total variance, highlighting correlations driven by geological characteristics of the well region.

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