Assessment of groundwater geochemistry and diffusion of hexavalent chromium contamination in an industrial town of Italy

Abstract

Groundwater contamination by hexavalent chromium (Cr (VI)) is currently a very serious and challenging issue. Therefore, in the present study, 108 shallow groundwater samples were collected during the years 2012 to 2015 (n = 27 samples each year) from an industrial town (Aosta) to assess the contamination status of the area. To evaluate the Cr (VI) concentration level, sources of pollutants and groundwater geochemistry of the study area, a combined approach of the multi-statistical and hydrogeochemical techniques were used. Furthermore, a geographic information system (GIS) was applied for the spatial distribution of Cr (VI) so that the most contaminated sites can be identified for a quick decision by policymakers. Results show that the groundwater chemistry was dominated by HCO₃^- and SO₄^2- in the anionic chemistry and Ca²⁺ and Na⁺ in the cationic chemistry, while Ca-Mg-HCO₃ and Ca-Mg-Cl-SO₄ were the main water types during the years 2012-2015 in the study area. The central part and some north-eastern parts of the Aosta town groundwater was contaminated with Cr (VI) and are unsafe for drinking use. Concentration levels of Cr (VI) in the groundwater were 0.09 μg/L (lowest value) and 165 μg/L (highest value) in the years studied, and the spatial analysis shows the diffusion of Cr (VI) to north-east direction from the source. Contamination of Cr (VI) in the groundwater was due to the superficial slag deposits from a steel company within the study area. This study would be helpful for current and future water resource management in the area concerned.

Keywords: Groundwater; Hexavalent chromium pollution; Hydrogeochemistry; Source evaluation; Spatial distribution.