The Maggiore Valley well field plays a fundamental role in supplying drinking water to a large territory of the Piedmont Region (northwestern Italy) and has been intensively exploited since the early twentieth century. This water resource is hosted in a deep, multilayered aquifer system. The main purpose of this study was to characterize the recharge processes of the deep aquifer through hydrochemical and isotopic assessments, as well as the water quality in the recharge and drainage areas. For this purpose, 128 physical–chemical analyses (major ions) and 50 isotopic analyses (δ¹⁸O and δ²H) were carried out on samples collected in shallow and deep aquifer complexes in two sampling campaigns in 2021. From the results, a hydrogeological conceptual model of recharge processes was developed. The chemical data confirm the presence of bicarbonate–calcium facies in most samples of the shallow and deep aquifer complexes. Clear hydrochemical differences were observed among the investigated sectors. The recharge areas were identified as (1) far zones, namely the shallow aquifer complex of the Cuneo Plain, and (2) the shallow and deep aquifer complexes with groundwater mixing in the riverside sector of Po Plain in the Turin area. The mixing of waters from the Cuneo Plain and Turin Plain was verified in the well field area. The isotopic values of the artesian well water also confirmed contributions from the Turin and Cuneo Alps. This study clarified the recharge processes, thereby defining potential pollutant pathways, and the results provide additional support for groundwater resource management and protection.

The Poirino Plateau (northwestern Italy) presents high contamination of the shallow aquifer due to intense agricultural practices and industrial activities. Many inhabitants have exploited shallow wells for personal purposes, coming into contact with contaminants. The aims of this study were to characterize groundwater contamination by heavy metals and nitrates, assess the noncarcinogenic and carcinogenic health risks for oral and dermal exposure in different receptor groups (children, adults, workers) and compare the noncarcinogenic and carcinogenic risk results with the regulatory limits and, therefore, if the actual regulatory limits are able to detect all potential situations of risk. For this purpose, 18 monitoring wells were collected in July 2022, and chemical–physical parameters and heavy metals were detected. The chemical data confirm a relevant anthropogenic contamination by nitrate and heavy metals. The estimated health risks are much higher in children, for oral exposure rather than dermal exposure for all the substances. The comparison between the results of the human health risk assessment and those in respect of threshold values confirms the existence of a transition condition. This condition, with concentrations below regulatory limits and above the noncarcinogenic or carcinogenic limits, reveals that the regulatory limits are not able to identify all the potential risk situations for the population.

The Perrot Spring (1300 m a.s.l.), located to the right of the Chalamy valley in the Monte Avic Natural Park (Valle d’Aosta, Italy), is an important source of drinking water for the municipality of Champdepraz. This spring is located on a large slope characterised by the presence of a Quaternary cover of various origins (glacial, glaciolacustrine, and landslide) above the bedrock (essentially serpentinite referred to the Zermatt–Saas Zone, Penninic Domain). Water emerges at the contact between the landslide bodies and impermeable or semi-permeable glaciolacustrine deposits. The aim of this study is to define the processes and recharge zones of this spring. The analysis of the data revealed the presence of two contributions to the Perrot Spring input: a spring thaw contribution defined by a small increase in flow and an autumn contribution from rainwater infiltration. The low average temperature and low variation of the annual temperature (4.8–6.5 °C) suggest a sufficiently deep flow circuit. Chemical analyses showed a groundwater chemistry consistent with the regional geology: the hydrochemical facies is calcium–magnesium bicarbonate and isotopic analyses (δ²H and δ¹⁸O) of rainfall and spring water suggested a recharge altitude of about 2100 m a.s.l. In conclusion, this study makes it possible to recognize the water inputs to the spring discharge and to delineate its recharge area, which can be proposed to implement strategies to protect the resource.

The concentrations of chemicals in the groundwater chemical values in the Piedmont Po Plain (NW Italy) show significant temporal variability and need to be characterised due to the lack of regional-scale assessments. The aim of this study was to analyse the trends (period 2000–2020) in the main physicochemical parameters and main ions in 227 wells in the shallow aquifer and to identify the potential causes. The identification of change points (points of sudden change) and comparisons with groundwater level variations were also performed. Results highlight general increasing trends for Na, Cl and HCO₃, decreasing trends for SO₄ and NO₃, stationary conditions for pH and heterogeneous behaviours for electrolytic conductivity, Ca and Mg. Change points occurred in at least 50% of the monitoring wells, mainly during the 2008–2011 period. The comparison between groundwater levels and chemistry highlights a direct proportionality. Superimposed processes that induce an absence of proportionality are shown. The comparison of results with those of previous studies conducted under similar conditions revealed similar variations.. In conclusion, the potential responsible factors (e.g., road-salt dissolution and agricultural practices) and the relevant role of groundwater level variation were identified.

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 –, SO4 2–, 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.

The precipitation constitutes one of the main sources of the groundwater resources. The chemical composition of precipitation is influenced both by natural and anthropic sources. For this reason, it is essential to monitor rainfall potentially able to influence groundwater quality. The Po Plain sector (NW Italy) is one of the most urbanized, industrialized and air polluted area in Europe but few studies have been conducted in this area, particularly in the Piedmont Region.The main purpose of this study was: I) to provide a preliminary assessment of quality and isotopic composition of rainwater in the western Po Plain, II) to show the spatial and temporal differences of rain chemical composition between the monitoring points, and III) to define the influence of rain to groundwater chemistry.A long-term trends on the groundwater concentration of NO3– and SO42– in the shallow aquifer on 227 monitoring points of the Regional Monitoring network database were conducted (2000-2020 period).In the last decades, in Europe a large effort was carried out to reduce sulphur and nitrogen emission in the atmosphere. This resulted in a sharp decrease in the deposition of SO42– and nitrogen compounds.The rain analysis of long-term trends in near regions, revealed a large proportion of significant decreasing trends in the concentration of both sulphate and nitrogen compounds.Actually also the analysis of groundwater long-term trends revealed a significant decreasing trends in the concentration of NO3– and SO42– in the shallow aquifer.A sampling campaigns was carried out during one year (September 2021 – September 2022) in 4 monitoring points located in the western Po Plain. Rainfall collection occurred every 2 months, for a total of 20 samples. Physical-chemical analyzes of the main ions and isotopic analyzes (δ18O, δ2H) were conducted for all samples.The period September 2021 – September 2022 was characterized by a rainfall deficit in the winter period in the NW Italy, recording a 62% reduction in rainfall (compared to the climatic average of the thirty year period 1981-2010).The processing of rainfall chemical data has shown different concentrations between the monitoring points and a temporal variability. High NO3– and SO42– concentrations were observed.Rainfalls sampled after the winter dry period (March-April samples) show higher ions concentrations (NO3– 13 mg/L, SO42– 4 mg/L) respect to other periods. Differences in rainfall samples depend on the location of the monitoring point (urban or rural areas).Isotopic data has shown different spatial and temporal isotopic signals, linked to the location and elevation of the monitoring points. In the δ18O/δ2H diagram all isotopic signals are not placed on the Local Meteoric World Line, potentially linked to climate change.The isotopic signals are within the ranges of previous studies (δ18O: -12,6/-6,2; δ2H: -82,15/-35,1 ‰ (min/max)).In conclusion, the rain ions concentrations are influenced by anthropic pollution, they are affected by dry periods and they appears to influence the concentration in groundwater.