Magnetic Resonance Imaging of Nonaqueous Phase Liquid Distribution in Unconsolidated Soils Using Discriminatory Freezing

Abstract

AbstractOrganic contaminants present as nonaqueous phase liquids (NAPLs) in the subsurface often pose a long‐term risk to human health and the environment. Investigating the distribution of NAPLs in porous media remains a major challenge in risk assessment and management of contaminated sites. Conventional soil coring and monitoring wells have been widely used over past decades as the primary means of subsurface investigation to determine NAPL extent. Known limitations of conventional approaches have led us to explore an alternative or a complementary technique to provide high‐quality information of NAPL source zone architecture. This work advances an imaging tool for a variety of organic NAPL contaminants in unconsolidated soils through magnetic resonance imaging (MRI) of frozen cores. Using trichloroethylene (TCE) and o‐xylene as model species, we illustrate that discriminatory freezing of water, while keeping the NAPL in a liquid state, enables high‐resolution qualitative delineation of NAPL distribution within porous media. This novel approach may help improve site conceptual models and consequentially lead to highly tailored, more efficient remedial measures.