Dear Colleagues,

In densely urbanized areas, groundwater constitutes an essential source of freshwater and contributes to the socioeconomic development of urban centers. Nevertheless, the ever-increasing demand for safe drinking water attributable to anthropogenic activities poses a serious threat to groundwater quality, also in relation to future water scarcity scenarios. Although several approaches have been developed to address the problem of urban aquifer pollution, the main challenges are:

• The identification of the most vulnerable areas and the potential sources responsible for groundwater contamination, considering the contribution of both historical anthropogenic activities and sources that are still active today;
• The distinction of main point sources (i.e., hotspots) from diffuse contamination, which is attributed to unknown small sources clustered in large areas and cannot be remediated;
• The delineation of contaminant plumes, which can seriously affect sensible targets (i.e., water supply wells).

Among the different approaches, GIS-based statistical techniques (e.g., logistic regression, weights of evidence), statistical analysis (e.g., cluster and multivariate analyses), numerical modeling (e.g., groundwater flow and contaminant transport models) and, more recently, stochastic modeling (e.g., null-space Monte Carlo) represent key tools for the assessment of quality deterioration of urban aquifers. The use and combination of these approaches can support water managers and public authorities in practical problems including the 1) identification of the source responsible for the contamination according to the pollution pays principle, 2) the delineation of the areas affected by a background level of contamination and not by a specific source of pollution, and 3) the implementation of strategies to remediate sources and protect intake areas.

The aim of this Special Issue of Sustainability is to provide an overview of the different and innovative approaches used to assess urban aquifer pollution, in order to gain additional and useful insights on groundwater resource protection

Dr. Loris Colombo
Dr. Pietro Mazzon
Dr. Licia Camilla Pollicino
Dr. Grzegorz Gzyl
Guest Editors

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• Groundwater flow and transport modelling
• Multivariate analysis
• Cluster analysis
• MODFLOW
• MT3DMS
• GIS
• Urban areas