Climate change impact on residual contaminants under sustainable remediation

Abstract

This study investigates the potential impact of climate change on residual contaminants in vadose zones and groundwater. We assume that the effect of climate changes can be represented by perturbations in the natural recharge through the aquifer system. We perform numerical modeling of unsaturated/saturated flow and transport and consider different performance metrics: contaminant concentrations at observation wells and contaminant export at the site's boundary. We evaluate the effect of increasing and decreasing recharge as well as the impact of potential failure of surface capping structures employed to immobilize vadose zone contaminants. Our approach is demonstrated in a real case study by simulating transport of non-reactive radioactive tritium at the U.S. Department of Energy's Savannah River Site. Results show that recharge changes significantly affect well concentrations: after an initial slight dilution we identify a significant concentration increase at different observation wells some years after t he recharge increase and/or the cap failure, as a consequence of contaminants' mobilization. This effect is generally emphasized and occurs earlier as the recharge increases. Under decreased aquifers' recharge the concentration could slightly increase for some years, due to a decrease of dilution, depending on the magnitude of the negative recharge shift. We identify trigger levels of recharge above which the concentration/export breakthrough curves and the time of exceedance of the Maximum Contaminant Level for tritium are remarkably affected. Moreover, we observe that the contaminant export at the control plane, identified as the risk pathway to the downgradient

Characterizing the Influence of Multiple Uncertainties on Predictions of Contaminant Discharge in Groundwater Within a Lagrangian Stochastic Formulation

“…There is a need to enhance our fundamental understanding of how contaminant source zone characteristics and aquifer recharge rates impact the risks associated with aquifer pollution. It is expected that climate change will impact aquifer recharge rates (O'Connell & Hou, 2015) which can potentially affect aquifer remediation campaigns as shown in Libera et al (2019). At the same time, the contaminant release history has a profound impact on transport and is often unknown.…”

“…Although hydrogeological heterogeneity has been recognized as a key control on the transport, there is a need to investigate the combined effect of physical heterogeneity, aquifer recharge, and source zone mass release rates on the probabilistic description of solute transport. For instance, aquifer recharge can impact Water Resources Research 10.1029/2020WR027867 plume mobility and remediation strategies (Libera et al, 2019). Recent works (e.g., Libera et al, 2019;O'Connell & Hou, 2015) raised concerns regarding the risks to site remediation due climate change since precipitation regimes are expected to change.…”

“…For instance, aquifer recharge can impact Water Resources Research 10.1029/2020WR027867 plume mobility and remediation strategies (Libera et al, 2019). Recent works (e.g., Libera et al, 2019;O'Connell & Hou, 2015) raised concerns regarding the risks to site remediation due climate change since precipitation regimes are expected to change. Recharge rates impact solute travel times and the macrodispersive behavior of the plume (e.g., Butera & Tanda, 1999;Destouni et al, 2001;Ezzedine & Rubin, 1997;Li & Graham, 1999;MacFarlane et al, 1983;.…”

Resilient remediation: Addressing extreme weather and climate change, creating community value

“…A recent study showed a potential impact of such climatic shifts on residual contaminants in soil and groundwater (Libera et al., ). The study found that the hydrological shifts influence contaminant concentrations in a complex manner, since increased infiltration, for example, could cause conflicting effects of both diluting and mobilizing contaminants.…”

Reactive Transport Modeling for Supporting Climate Resilience at Groundwater Contamination Sites

“…The model is developed and applied at the Department of Energy (DOE)'s Savannah River Site (SRS) F-Area Seepage Basins, South Carolina (SC), USA, where various metals and radioactive contaminants exist in the soil and groundwater since 1950s. This is the same site studied by Libera et al (2019). With extensive geophysical data for subsurface characterization and comprehensive groundwater chemistry and water level datasets at the 90 SRS F-Area, the development of a subsurface model can be considered as a testbed for flow and transport studies (Flach, 2004;Bea et al, 2013;Sassen et al, 2012;Wainwright et al, 2014Wainwright et al, , 2015Wainwright et al, , 2016Denham and Eddy-Dilek, 2017;Libera et al, 2019).…”