Evaluating The Representativeness Of Suction Lysimeter For Sampling Pfas Porewater Concentration In The Vadose Zone
Presenter: Min Ma P121
Co-Author(s): Jicai Zeng; Bo Guo
Advisor(s): Bo Guo
1Hydrology & Atmospheric Sciences
Per- and poly-fluoroalkyl substances (PFAS) have accumulated significantly in the vadose zone at many sites due to decades of contamination. This poses critical risks as PFAS can leach downward driven by infiltration events to contaminate the groundwater underneath. Understanding and quantifying the leaching potential of PFAS in the vadose zone requires direct sampling and measurement of PFAS concentrations in the soil and porewater. Suction lysimeters have been widely used for sampling and measuring porewater chemistry of many solutes in the vadose zone. However, these suction lysimeters face a series of unique challenges when applied to sampling the porewater concentrations of PFAS due to the strong partitioning of PFAS to the air-water interfaces. For example, the suction may lead to disturbances to the soil porewater concentration, due to the change of local wetting conditions. We employed an advanced three-dimensional mathematical model to simulate the sampling process under a wide range of scenarios representative of field applications of suction lysimeters. Our results reveal that the sampling errors can be significant for some longer-chain PFAS—up to 60% depending on the specific operative and environmental conditions. The detailed analyses and insights can be used to develop guidance and support for improving field sampling accuracy, which will ultimately contribute to cost-effective management and remediation of PFAS-contaminated sites.