Literature provides only a few examples of contamination of groundwater with microplastics, mainly investigated using a chemical approach. Little importance is given to the hydrogeological processes able to affect the contamination, such as river–groundwater interactions. This study was carried out with two aims. The first aim is the formulation of a method with a high result-to-cost ratio, based on the hydrogeological aspects of the investigated area. Microplastics were extracted from samples through filtration and successively counted and characterized morphologically through analysis of optical microscopy images. The second aim is to evaluate the presence of microplastics in some portions of an alluvial aquifer using this methodology. Microplastics in groundwater showed a higher circularity and Feret diameter than those found in surface waters, indicating that in porous aquifers the transport is likely more influenced by the microplastics’ shape than by their size. The aquifer recharge did not modify the microplastics’ characteristics in groundwater, whereas in surface water the flood wave promoted the resuspension of microplastics with lower circularity. These findings provide new pieces of evidence on the presence and transport of microplastics in both groundwater and surface waters, underlining how the hydrogeological characteristics of the area can be one of the main drivers of microplastics’ contamination.

Urban areas exercise numerous and strong pressures on water bodies, implying that different external anthropogenic factors also stress groundwater. Sewerage networks play an important role, being the place of wastewater flow. When sewerage deterioration conditions occur, aquifers can be contaminated by contaminants contained within wastewater. The study aims to verify the impact of sewerage leaks in urban semi-confined aquifers through a multidisciplinary approach. Geological, hydrogeological, hydrochemical, microbiological, and biomolecular investigations are carried out in a test site close to a sewer pipe, from February to October 2022. Microbiological analyses are carried out on a monthly basis, contextually to hydraulic head measurements in purpose-drilled piezometers. The presence of sandy intercalations and the prevalence of silt within the outcropping (about 10 m thick) aquitard makes the aquifer vulnerable to percolation from leaky sewers, therefore causing persistent microbial contamination in groundwater. The presence of fecal indicators (including pathogenic genera), corrosive and human-associated bacteria markers, is detected. The magnitude of microbiological impact varies over time, depending on hydrogeological factors such as dilution, hydrodynamic dispersion, and variation of the groundwater flow pathway at the site scale. As for personal care products, only Disodium EDTA is detected in wastewater, while in groundwater the concentrations of all the analyzed substances are lower than the instrumental detection limit.

The occurrence of emerging pollutants (EPs) such as pharmaceuticals and personal care products (PPCPs) has raised serious concerns about the possible adverse effects on ecosystem integrity and human health. Wastewater treatment facilities appear to be the main sources of PPCPs released in aquatic environments. This research examines the effectiveness of groundwater microbial community activities to remove phenoxyethanol (Phy-Et), currently exploited as a preservative in many cosmetic formulations at a maximum concentration of 1% but which has shown, at higher levels of exposure, adverse systemic effects on animals. Mesocosm experiments were carried out for 28 days using two different concentrations of the substance (5.2 mg/L and 27.4 mg/L). The main results obtained through chemical and microbiological investigations revealed a significant Phy-Et reduction (≈100% when added at a concentration of 5.2 mg/L and ≈84% when added at a concentration of 27.4 mg/L), demonstrating that some autochthonous microorganisms in the analyzed samples played a “key role” in removing this compound, despite its proven antimicrobial activity. Nevertheless, the decrease in the “natural attenuation” efficacy (≈16%) when using higher concentrations of the chemical suggests the existence of a “dose-dependent effect” of Phy-Et on the process of biodegradation. Biomolecular investigations carried out through next-generation sequencing (NGS) revealed (i) the presence of a significant fraction of hidden microbial diversity to unravel, (ii) variations of the composition and species abundance of the groundwater microbial communities induced by Phy-Et, and (iii) a biodiversity reduction trend correlated to the increase of Phy-Et concentrations. Overall, the preliminary information obtained from the experiments carried out at the laboratory scale appears encouraging, although it reflects only partially the complexity of the phenomena that occur in natural environments and influences their “auto-purification capability”. Accordingly, this research paves the way for more in-depth investigations to develop appropriate tools and protocols to evaluate the occurrence and fate of Phy-Et in nature and assess the impact of its release and the effects of long-term exposure (even at low concentrations) on ecosystems and health.

In recent years, there has been a surge in interest concerning emerging contaminants, also known as contaminants of emerging concern (CECs), due to their presence in environmental matrices. Despite lacking regulation, these chemicals pose potential health and environmental safety risks. Disodium EDTA, a widely utilized chelating agent, has raised concerns regarding its environmental impact. The present work aimed to verify the presence of Disodium EDTA at the exit of eight wastewater treatment plants discharging into some losing streams flowing within a large alluvial aquifer. Conducted in the Province of Parma (Northern Italy), the research employs a multidisciplinary approach, incorporating geological, hydrogeological, chemical, and microbial community analyses. Following a territorial analysis to assess industries in the region, through the use of ATECO codes (a classification system for economic activities), the study investigated the concentration of Disodium EDTA in effluents from eight diverse wastewater treatment plants, noting that all discharges originate from an activated sludge treatment plant, released into surface water courses feeding the alluvial aquifer. Results revealed detectable levels of Disodium EDTA in all samples, indicating its persistence post-treatment. Concentrations ranged from 80 to 980 µg/L, highlighting the need for further research on its environmental fate and potential mitigation strategies. Additionally, the microbial communities naturally occurring in shallow groundwater were analyzed from a hydrogeological perspective. The widespread presence of a bacterial community predominantly composed of aerobic bacteria further confirmed that the studied aquifer is diffusely unconfined or semi-confined and/or diffusely fed by surface water sources. Furthermore, the presence of fecal bacteria served as a marker of diffuse leakage from sewage networks, which contain pre-treated wastewater. Although concentrations of Disodium EDTA above the instrumental quantification limit have not been found in groundwater to date, this research highlights the significant vulnerability of aquifers to Disodium EDTA. It reveals the critical link between surface waters, which receive treated wastewaters impacted by Disodium EDTA, and groundwater, emphasizing how this connection can expose aquifers to potential contamination. At this stage of the research, dilution of wastewaters in surface- and groundwater, as well as hydrodynamic dispersion within the alluvial aquifer, seem to be the main factors influencing the decrease in Disodium EDTA concentration in the subsurface below the actual quantification limit. Consequently, there is a pressing need to enhance methodologies to lower the instrumental quantification limit within aqueous matrices. In a broader context, urgent measures are needed to address the risk of diffuse transport of CECs contaminants like Disodium EDTA and safeguard the integrity of surface and groundwater resources, which are essential for sustaining ecosystems and human health.

Few hydrogeological studies have focused on possible per- and poly-fluoroalkyl substance (PFAS) contamination in groundwater with particular attention to the role of hydraulic interconnections and to the interdigitations present between shallow and deep aquifer layers in heterogeneous alluvial systems. In general, deeper groundwater is considered chemically safer and less impacted by contamination, especially in multilayer aquifers characterized by low permeability apparently confining horizons. Therefore, this research analyzed PFAS in groundwater at depths ranging from 20 to 120 m below ground level, combining stratigraphic, hydrogeological, and chemical data with GIS mapping to identify industrial activities potentially contributing to PFAS contamination using the cross-checking methodology. During the second survey, the monitoring network was extended along a hydrogeological transect, including two springs located upstream and downstream of the deep wells, to assess PFAS concentration in shallow groundwater and the possible transfer along the groundwater flow path. The intra-site comparative analysis reveals, for the same sampling locations, a differentiation in the PFAS profiles detected across the two monitoring campaigns, indicating a temporal evolution in the chemical composition. Furthermore, chemical results show the presence of PFAS exclusively in deep monitoring wells, confirming a spatially heterogeneous distribution within the aquifer system. These results highlight both the temporal and spatial evolution of PFAS concentration, suggesting a complex contaminant migration pathway along preferential gravel and sand horizons in deeper aquifer layers. The conceptual hydrogeological model confirmed hydraulic interconnections among aquifer layers and identified zones of higher vulnerability to contamination. The analysis of possible PFAS migration pathways at the basin scale raised some questions about the influence of wells features and management practices on PFAS distribution in shallow and deep groundwater. The findings of this research contribute to environmental sustainability, providing initial insights for measuring and managing the presence and pathways of PFAS in deep alluvial aquifers.