Model-Based Analysis of the Link between Groundwater Table Rising and the Formation of Solute Plumes in a Shallow Stratified Aquifer

Abstract

Groundwater table rising (GTR) represents a well-known issue that affects several urban and agricultural areas of the world. This work addresses the link between GTR and the formation of solute plumes from contaminant sources that are located in the vadose zone, and that water table rising may help mobilize with time. A case study is analyzed in the stratified pyroclastic-alluvial aquifer near Naples (Italy), which is notoriously affected by GTR. A dismissed chemical factory generated a solute plume, which was hydraulically confined by a pump-and-treat (P&T) system. Since 2011, aqueous concentrations of 1,1-dichloroethene (1,1-DCE) have been found to exceed regulatory maximum concentration levels in monitoring wells. It has been hypothesized that a 1,1-DCE source may occur as buried waste that has been flushed with time under GTR. To elucidate this hypothesis and reoptimize the P&T system, flow and transport numerical modeling analysis was developed using site-specific data. The results indicated that the formulated hypothesis is indeed plausible. The model shows that water table peaks were reached in 2011 and 2017, which agree with the 1,1-DCE concentration peaks observed in the site. The model was also able to capture the simultaneous decrease in the water table levels and concentrations between 2011 and 2014. Scenario-based analysis suggests that lowering the water table below the elevation of the hypothesized source is potentially a cost-effective strategy to reschedule the pumping rates of the P&T system.

A GIS-Based Hydrogeological Approach to the Assessment of the Groundwater Circulation in the Ischia Volcanic Island (Italy)

“…The interpolation of one kind or another (e.g., linear) of water level data, measured at the same time in the available observation wells of a given aquifer, allows contours of the potentiometric surface to be drawn (Bear, 2007). Therefore, many software programs have been developed for drawing contour maps, and properly designed and constructed mathematical models are able to predict the water levels by solving the partial differential equations which govern the groundwater flow (e.g., Domenico and Schwartz, 1998;Ochoa-Gonzáleza et al, 2015;Varisco et al, 2021). Geospatial technologies have become an effective tool for monitoring, mapping, and modeling water resources as well as for volcanic risk evaluation and management and emergency planning due to their capability to store, retrieve, analyze, and display data that are characterized spatially or geographically (Pareschi et al, 2000;Felpeto et al, 2007;Díaz-Alcaide and Martínez-Santos, 2019 and references therein;Abdalla et al, 2020;Bellucci Sessa et al, 2021).…”

Assessing a Large-Scale Sequential In Situ Chloroethene Bioremediation System Using Compound-Specific Isotope Analysis (CSIA) and Geochemical Modeling

“…Lack of model-based analyses of sequential ISBs. Mathematical models are particularly important to provide quantitative support for decision makers [4,[10][11][12][13][14]. As the usefulness of mathematical tools was already demonstrated for single ISBs [14][15][16][17], we maintain that such models could also be fundamental for the correct design and implementation of sequential ISBs.…”