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Groundwater is the environmental compartment very often involved in the broader issues related to contaminated sites characterization and reclamation. It is not uncommon to find areas in which some substances directly linked to the petrographic composition of the aquifer reach high values exceeding the limits set by the regulations. These concentrations are defined as Natural Background Levels (NBL) and the need to quantify their real contribution, in areas subject to strong anthropogenic pressures, represents an emerging problem. Global statistical analyses and laboratory testing are proposed here to distinguish between the impacts of different forcing influencing water quality in hydrogeological systems. The study focus on the application of a methodology based on the Component Separation analysis for the NBL estimation of selected chemical species in potentially contaminated aquifers flowing in the proximity of landfill areas, and on the subsequent validation of the results through experimental studies of field samples. A site located in Calabria, Italy, and constituting a typical example of an aquifer which has been subjected to possible contact with the leachate produced by waste degradation is considered. The work is keyed to NBLs characterization of aluminum, iron and manganese and to the identification of their natural component for a proper environmental assessment of the site. Estimated NBLs are consistent with the geochemical composition of site samples. The adopted methodology can represent a useful instrument to distinguish effective anthropogenic contamination from natural conditions and to define realistic environmental clean-up goals., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The estimation of natural background levels (NBLs) of dissolved concentrations of target chemical species in subsurface reservoirs relies on a proper assessment of the effects of forcing terms driving flow and transport processes taking place within the system and whose dynamics drive background concentration values. We propose coupling methodologies based on (a) global statistical analyses and (b) numerical modeling of system dynamics to distinguish between the impacts of different types of external forcing components influencing background concentration values. We focus on the joint application of a statistical methodology based on Component Separation and experimental/numerical modeling studies of groundwater flow and transport for the NBL estimation of selected chemical species in potentially contaminated coastal aquifers. We consider a site which is located in Calabria, Italy, and constitutes a typical example of a Mediterranean coastal aquifer which has been subject to intense industrial development. Our study is keyed to the characterization of NBLs of manganese and sulfate and is geared to the proper identification of the importance of a natural external forcing (i.e., seawater intrusion) on NBL assessment. Results from the Component Separation statistical approach are complemented by numerical simulations of the advective-dispersive processes that could influence the distribution of chemical species (i.e., sulfate) within the system. Estimated NBLs for manganese are consistent with the geochemical composition of soil samples. While Component Separation ascribes the largest detected sulfate concentrations to anthropogenic sources, our numerical modeling analysis suggests that they are mainly related to the natural process of seawater intrusion. Our results indicate that the use of statistical methodologies in complex groundwater systems should be assisted by a detailed characterization of the dynamics of natural (and/or induced) processes to distinguish effective anthropogenic contamination from natural conditions and to define realistic environmental clean-up goals., (Copyright © 2014 Elsevier B.V. All rights reserved.)