Geochemical, geostatistical and time series analysis techniques as a tool to achieve the Water Framework Directive goals: An example from Piedmont region (NW Italy)

In this study, geochemical data processing and statistical/geostatistical techniques were coupled to achieve Water Framework Directive goals, collecting useful information from a complex database. Considering the Greater Turin metropolitan area, located in North-Western Italy, chemical data of 135 wells sampled and collected from 2000 to 2018 by the Environmental Protection Agency of Piedmont were analyzed. Both the processes that determine the groundwater chemical composition and the origin and evolution of groundwater were decoded and understood. The presence of two different components in the foothill aquifer system investigated was found. A bicarbonate alkaline earthy type component, linked with different degrees to phenomena of water-rock interaction, and a chlorinated type component related to nitrates, whose effects related to human activities can be recognized. This last component was mapped by using geostatistical techniques to define the most critical zones of the study area. Time series analysis on chlorides and nitrates displayed the presence of statistically significant increasing trends in some areas of the Turin plain. This study shows that the combining of geochemical approach, geostatistical techniques, and time series analysis can be used as reliable tools to understand geochemical processes acting on the system, to identify temporal and spatial hydrochemical variability, as well as to forecast water quality evolution. In this perspective, the multi-disciplinary approach developed in this study represents a reliable methodology for extracting useful information from a complex database and achieving the Water Framework Directive goals.