Spatio-temporal variability of groundwater hydrochemical features in different hydrogeological settings in Piedmont and Campania regions (Italy), a comparative study

The spatio-temporal evolution of groundwater chemistry has seen an increase in interest over the last decade at a global level. Identifying and discerning the sources of the natural and anthropogenic compounds and the actual hydrochemical processes, as well as their evolution, is essential to support a sustainable planning for managing and protecting groundwater resources at the present time and in the future. The main objective of this study is the comparison of two study areas in Italy (Piedmont and Campania Regions), different in their geographical and geological contexts and climate conditions, to highlight the similarities and differences in the hydrogeochemical behavior in space and time. Three main ions were considered (NO3–, SO42–, Na+) and analyzed to identify the sources and hydrochemical processes responsible for their spatial distribution in the 2015-2020 period and evaluate the existence and the potential causes of trends in their concentration for the 2000-2020 period. Results highlight specific factors and processes distinguishing the spatial distribution and temporal variability of ion concentrations in Piedmont and Campania study areas. These processes are mainly related to the geological and geographical features of the study areas. In both areas, a significant influence of anthropogenic pressures emerges for both spatial and temporal evolutions, with remarkably increasing trends in NO3– concentrations. In conclusion, some factors and processes emerge as site-specific, mainly related to the geological aspects and natural hydrochemical processes, whereas others are in common (i.e., anthropogenic impacts); thus, reinforcing the advantage of making comparative studies.