Affiliation:
1. Laboratory of Environmental Engineering, Department of Civil Engineering and Computer Science Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy
Abstract
222Radon (Rn) was proposed in the late 1990s as a naturally occurring tracer for light non-aqueous phase liquids (LNAPLs) in the subsurface, due to its preferential partitioning behavior in the non-aqueous phase, resulting in a reduction in Rn activities in areas with LNAPLs in the subsurface compared to unimpacted areas (Rn deficit). The Rn deficit technique emerged as a cost-effective, non-invasive, and sustainable method to rapidly identify and quantify LNAPLs, for the characterization and monitoring of contaminated sites. This paper presents an overview of the technique and its field applications, with a specific focus on the use of the method in the vadose zone based on soil gas Rn measurements. Although various configurations have shown favorable outcomes, limitations persist in the application of the soil gas Rn deficit technique. Deep LNAPL contamination, soil matrix heterogeneity, and temporal variations in Rn emissions pose challenges to quantitative evaluations of LNAPL contamination. Recognizing these factors is crucial for site-specific assessments. This review aims to highlight both the strengths and limitations of the method, providing insights into potential areas for future research while acknowledging the positive outcomes achieved in different configurations over the past decades.
Reference147 articles.
1. US EPA (1995). Ground Water Issue: Light Nonaqueous Phase Liquids, US EPA.
2. García-Rincón, J., Gatsios, E., Lenhard, R.J., Atekwana, E.A., and Naidu, R. (2024). Advances in the Characterisation and Remediation of Sites Contaminated with Petroleum Hydrocarbons, Springer International Publishing. Environmental Contamination Remediation and Management.
3. CL:AIRE (2014). An Illustrated Handbook of LNAPL Transport and Fate in the Subsurface, CL:AIRE.
4. Small Purge Method to Sample Vapor from Groundwater Monitoring Wells Screened across the Water Table;Sweeney;Groundw. Monit. Remediat.,2017
5. US EPA (2004). A Decision-Making Framework for Cleanup of Sites Impacted with Light Non-Aqueous Phase Liquids (LNAPL), US EPA.