The science of the fate, transport and toxicity of per- and polyfluoroalkyl substances (PFAS) has progressed to the point that water quality guidelines have been promulgated in Canada for some of these compounds and more are being developed or considered. This will likely result in the identification of more PFAS-contaminated sites. Sampling and analytical tools to reliably measure PFAS in water and other environmental media have improved in the last few years; however, many grab sampling techniques are time-consuming, cause disturbance of the water column and generate volumes of contaminated water that need disposal. Furthermore, grab sampling approaches only provide a snapshot of PFAS concentrations.

Passive samplers overcome many of these issues and can be valuable in site investigation, risk assessment and management. Passive samplers are a valued tool for evaluating other hydrophobic contaminants, such as polychlorinated biphenyls and polyaromatic hydrocarbons. A passive sampler is a physical medium such as a polymer with a predictable affinity for the analyte of interest. This physical medium is loaded into a device suitable for deployment (e.g., down a groundwater well or embedded in sediment). Because the uptake of hydrophobic contaminants is rather slow (on the order of weeks or months), the results represent time-integrated concentrations and provide better long-term site characterization. Additionally, accumulation of the analyte by the passive sampler medium allows improved detection limits when compared to traditional water sampling. Furthermore, passive samplers accumulate only the freely dissolved (most bioavailable) fraction of the contaminant, providing better insights into the ecological risk than the total concentrations which tend to overestimate the magnitude of risk.

With these benefits in mind, a passive sampler for PFAS has been designed. The research process involved preliminary trials to identify a suitable physical medium. Adsorption experiments were then conducted for 15 PFAS analytes ranging from anionic carboxylic acids and sulfonates of different chain lengths to PFAS precursors to determine their uptake kinetics and adsorption isotherms. The equilibrium between passive sampler and the sampled water was achieved in less than seven days for most of the analytes. The adsorption behaviour varied significantly between the analytes. The longer chain compounds demonstrated higher sorption than the shorter chains, and the sulfonates showed higher sorption compared to carboxylates. Sorption of PFAS onto the passive sampler was also affected by the water pH, ionic strength, and dissolved organic matter, which indicates the importance of considering these variables in PFAS site investigation and risk management planning.

This presentation will include the details on the PFAS passive sampler development as well as a discussion on how passive samplers can benefit PFAS site investigations and why results from passive samplers are an important line of evidence for ecological risk assessments. If available in time for the presentation, the results from a field demonstration to be conducted will also be presented. The field data will be discussed in terms of the benefits, limitations, and future refinement needs of the technology and its applicability in site investigation and risk assessment.

Eliza Kaltenberg, Research Scientist, Environmental Assessment Group, Battelle Memorial Institute
Dr. Eliza Kaltenberg is a Research Scientist with Battelle's Environmental Assessment Group. The majority of her current work focuses on assessments of hydrophobic organic compounds in sediments and water. She has been also a part of Battelle's research group working on advancement of PFAS sampling methods. Eliza’s research interests include aqueous and sediment geochemistry, hydrophobic contaminant partitioning and bioavailability, the influence of bioturbation of early diagenesis processes, and the role of sediments in nutrient retention. She worked on several projects regarding development of new analytical methods for aqueous and sediment samples, where she utilized a combination of passive sampling, colorimetry, and fluorescent tracers to answer the emerging questions and needs in an innovative way.

Stefano Marconetto, Global PFAS Practice Leader, Golder 
Stefano Marconetto is Golder’s global PFAS practice leader with 10 years of experience with the characterization and remediation of PFAS impacted sites. Mr. Marconetto’s technical focus is primarily on detailed site characterization, fate&transport assessment and conceptual site model development, but his expertise also includes remedial options evaluation, feasibility assessment, remedial action plan development and implementation at military bases, firefighting training facilities, airports, manufacturing plants, power plants and waste disposal sites in North America and abroad. He has also provided technical training as well as support to clients in their liaison with project stakeholders on PFAS related issues. He authored presentations and guidance documents on PFAS, is currently an active member of the ITRC PFAS team and is involved in several research projects in collaboration with prestigious universities and industrial partners on PFAS fate&transport and remediation.

Repeated discharges of aqueous film forming foams (AFFFs) in designated firefighting training areas over decades are closely linked to severe soil and groundwater contamination by per- and polyfluoroalkyl substances (PFAS). Increasingly stringent regulations require mitigation measures and treatment technologies that can effectively control the spread of PFASs or clean up impacted sites. A broad array of treatment technologies have been developed for treating contaminated water, while few effective soil treatment technologies are available to contaminated site practitioners. The literature has documented that modified clays, produced by inserting organic cations (e.g., quaternary ammonium surfactant) in the exchange sites of smectite clays, can immobilize a range of organic contaminants in soil remediation. The goal of this study is to evaluate the performance of modified clays as a soil amendment in reducing the mobility or leachability of the dozens of PFASs detected in contaminated soils.

The PFAS profiles of four contaminated sandy soils were first characterized using UHPLC coupled with high-resolution mass spectrometry to demonstrate the significant presence of anionic, cationic and neutral PFAS. In the first stage, a one-step batch test, which was modified based on the US EPA Toxicity Characteristic Leaching Procedure (TCLP), was used to determine the effect of sorbent dosage, equilibration time, and potential microbial activities using a heavily contaminated soil. The significant reduction (95~99%) of anionic PFAS from the soil leachate, including perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorooctane carboxylate (PFOA), can be achieved in 1-3 days with a dosage as low as 0.5% (w/w). There was also a significant reduction of several cationic and neutral PFAS (sulfonamide and quaternary ammonium), but a higher dosage was necessary. In the second stage, a comparative assessment was conducted between the modified clay, natural clay, granular activated carbon, and biochar. We will also assess the performance of the modified clay using a long-term unsaturated soil setup to simulate field conditions. We will discuss how the findings may contribute to developing low-cost and easy-to-implement soil remediation technology for PFAS-contaminated soils.

Dr. Bei Yan is a postdoctoral researcher supervised by Prof. Jinxia Liu. His research focuses on the application and mechanism of adsorption, developing and characterizing adsorbent materials, optimizing water and wastewater treatment processes, and molecular simulation of the adsorption process.

Dr. Jinxia Liu is an Associate Professor in environmental engineering and Chwang-Seto Faculty Scholar. She has an extensive portfolio of PFAS research include developing PFAS analytical methods, elucidating sorption mechanisms, assessing precursor biotransformation and microbial defluorination, and developing PFAS remediation technologies. She also studies the water quality issue and micropollutants for future wastewater treatment processes that are decentralized, source separated, and recover energy and nutrients.

Despite the widespread occurrence of per- and polyfluoroalkyl substances (PFAS) contamination in bedrock formations, the fate and transport of these contaminants in fractured bedrock remains unexplored. Fractured bedrock formations are complex, dominated by flow-through fractures and exhibit much different characteristics than soils and sediments. It is currently unclear whether distribution coefficients, retardation factors and sorption mechanisms of PFAS to soils and sediments are applicable to fractured bedrock formations.

To address this knowledge gap, a series of laboratory experiments was conducted to study the sorption of a suite of PFAS to rock. Crushed and re-wetted Lockport Dolostone was used to evaluate sorption kinetics, mechanisms, and competition for a suite of 13 PFAS (C4-C12) with varying functional head groups (carboxylates, sulfonates and sulfonamide). For long chain PFAS (C8-C12 for carboxylated or C6-C12 for sulfonated) sorption increased with increasing chain length, suggesting hydrophobic-like interactions to be the predominant sorption mechanism. For short chain PFAS (C4-C7 for carboxylated or C4-C5 for sulfonated) sorption was not correlated to chain length, potentially due to competition between short and long chain compounds for available sites. This phenomenon has not been observed in previous sorption studies conducted using soils and sediments, suggesting that PFAS fate and transport in fractured bedrock formations is likely different than in soils and sediments. Additionally, sorption of long chain length compounds exhibited two different behaviours depending on chain length, suggesting that long chain length compounds should be subdivided into intermediate chain length compounds and long chain length compounds (C10-C12). Sorption of sulfonated PFAS was found to be greater than sorption of carboxylate or sulfonamide analogs with the same carbon chain length, suggesting that electrostatic forces also play a role in sorption to these rock samples. This is the first data for sorption of PFAS to rock and thus represent the first step towards evaluating PFAS fate and transport in fractured bedrock aquifers.

Omneya El-Sharnouby, Geosyntec Consultants Inc. 
Dr. Omneya El-Sharnouby is a post-doctoral fellow in Civil and Environmental Engineering at Queen’s University. She accomplished a doctorate degree in Civil and Environmental Engineering from Western University in developing novel nanometal based treatments for groundwater remediation from carcinogenic chlorinated organic contaminants, specifically 1,2-dichloroethane. Omneya’s experience with contaminants expands to include the emerging carcinogenic contaminants, PFAS. She is participating, with the Royal Military College of Canada, in the development of soil impacted PFAS treatments as well as laboratory analysis of PFAS contaminated water and soil samples from industrial, municipal and military based sites. Omneya is also researching the fate and transport of selected PFAS compounds in fractured bedrock formations. Additionally, she is currently developing a novel nanometal based treatment in collaboration with Golder and Imperial Oil for the destruction of PFAS impacted groundwater with potential application on surface water as well as industrial and municipal wastewater.