Sustainable Remediation in Complex Geologic Systems

Abstract

Sustainable remediation has been increasingly regarded as a promising alternative in recent years. It considers net environmental impacts such as energy use, greenhouse gas emission, and waste reduction. Passive in situ remediation or natural attenuation are the key component of sustainable remediation often intended to minimize the net environmental impacts. However, leaving contaminants in the subsurface requires the increased burden of proof to show that plumes are stable and residual contaminants do not pose a significant health risk. Particularly in complex geological environments and for actinide species with complex geochemical behaviors, it is difficult to ensure the system stability as well as to predict the future plume conditions. This article presents recent scientific advances to support sustainable remediation in complex geological systems, including site characterization techniques, hydrological and geochemical model developments, and numerical simulations. In particular, we highlight the recent developments in non‐invasive geophysical characterization as well as computationally efficient geochemical models for describing uranium and other reactive species. We demonstrate this approach using the extensive data and models from the Savannah River Site F‐area, which has been contaminated by low‐level radioactive waste solutions including uranium, tritium, and other radionuclides.

Improving Long-term Monitoring of Contaminated Groundwater at Sites where Attenuation-based Remedies are Deployed

“…Predictive contaminant transport modeling has long been used in all stages of groundwater monitoring (e.g., Mangold and Tsang 1991;Loaiciga et al 1992;Reed et al 2000), and it will be an integral aspect of the new long-term monitoring strategy. Contaminant transport modeling has been improved dramatically in recent years, thanks to highperformance computing (e.g., Bea et al 2013;Wainwright et al 2019). Transport modeling will also benefit from the increasing amount of observations that will improve their parameterization, validation, and/or calibration.…”

Understanding and Predicting Vadose Zone Processes

“…To capture complex vadose zone characteristics, signifi cant advances have been made in subsurface characterization techniques which are non-invasive, have fi ner resolution and capture a large spatial extent (Wainwright et al 2018). In particular, these include in situ water, solute and gas monitoring, geophysical and remotely sensed observations, as well as weather data, which all offer diverse sets of data.…”