Michael Healey will present a poster “The Development of a Diffusion-based Equilibrium Passive Sampler for PFAS Detection and Exposure Assessment in Sediment Pore Water and Surface Water” and Alex Sweett will present a poster “Peeping Into Deoxygenation: Experiments to Determine Effects of Oxygen on Peeper Samplers” at SETAC’s North America 43rd annual meeting in Pittsburgh, Pennsylvania on Tuesday November 15, 2022.

Michael’s co-authors are Brent Pautler, Alex Sweett, Iryna Ilina and Jeff Roberts (SiREM), Anh Pham & Blessing Medon (University of Waterloo), Florent Risacher, Lisa D’Agostino, Rachel Zajac-Fay & Jason Conder (Geosyntec Consultants), Jeremy Gauthier & Scott Mabury (University of Toronto), Amila O. De Silva (Environment and Climate Change Canada, Andrew Patterson, Patricia McIsaac & Robert Mitzel (Eurofins Environment Testing America).

Alex’s co-authors are Brent Pautler (SiREM), Haley Schneider, Florent Risacher & Jason Conder (Geosyntec Consultants), Andrew Jackson (Texas Tech University).

Michael is the Treatability and SP3™ Services Supervisor at SiREM with eight years of experience. Michael has managed numerous bench-scale studies evaluating remediation technologies for contaminants including chlorinated solvents, petroleum hydrocarbons, emerging contaminants and other recalcitrant compounds in soil, sediment, and groundwater. Michael has several years of passive sampling experience and was a lead member in the development and commercialization of the SP3™ sampler.

Alex is the Analytical Chemistry and Passive Sampling Laboratory Technician and supports SiREM’s passive sampling customers while contributing to the development and validation of new passive sampling products and services.

SETAC is a not-for-profit, worldwide professional organization composed of about 5,000 individuals and institution in more than 90 countries dedicated to the study, analysis and solution of environmental problems, the management and regulation of natural resources, research and development and environmental education.

SiREM Participation

The Development of a Diffusion-based Equilibrium Passive Sampler for PFAS Detection and Exposure Assessment in Sediment Pore Water and Surface Water

 Abstract

Per-and Polyfluoroalkyl Substances (PFAS) have emerged as a concern in the environment due to their persistence, bioaccumulation in living organisms, and toxicity. The established sampling protocols and PFAS concentration determination in sediment and surface water currently only captures the total concentration at a single timepoint and represents the entire mass of PFAS present, which may result in an overestimation of the bioavailable PFAS exposure to human and ecological receptors. Equilibrium passive sampling is a popular approach used to assess bioavailability and risk through the dissolved phase of contaminants but as PFAS are emerging contaminants, researchers have only started investigating potential passive sampling solutions. Given their partial water-solubility and the ability of analytical laboratories to detect trace amounts of PFAS in water, a diffusion-based equilibrium passive sampler was hypothesized to be a good passive sampling device candidate. When deployed, analytes dissolved in the water or sediment equilibrate with the water in the sampler through the semi-permeable membrane. Through a series of bench-scale laboratory experiments,  factors affecting the migration of several carboxylate and sulfonate PFAS into a diffusion cell were tested including the type of membrane filter, filter size, and solution chemistry. The results of these experiments suggested that the uptake of PFAS into the sampler was the fastest with polycarbonate membrane-based samplers, that the solution chemistry did not influence the PFAS uptake, PFAS were not lost to sorption or was not produced from sampler materials and that this sampler could be used to monitor multiple PFAS compounds.

The laboratory validated sampler was further tested in an in-situ field pilot to measure PFAS in sediment porewater and surface water. Targeted analytical results (Modified EPA 537, EPA 1633) were successful and suggested that equilibrium was reached in 14 days for surface water, an average 75% equilibrium for all target compounds detected in porewater after 28 days and were all within a factor of 2 or less with averaged grab sample results. Non-targeted analysis from the samplers showed more diversity in species and the applicability for detection of additional PFAS analytes with this sampler. Future experiments include direct comparison with tissue samples to further validate the relationship between passive sampling results and exposure, risk and bioaccumulation.

Peeping Into Deoxygenation: Experiments to Determine Effects of Oxygen on Peeper Samplers

 Abstract

Dialysis passive samplers (i.e. peepers) have been extensively studied and are a simple design that allows an ultrapure water solution to come to equilibrium with the surrounding sediment porewater via diffusion through a semi-permeable membrane. Upon retrieval, the water within the sampler is subjected to laboratory analysis for the target analytes by a standardized method. To date peepers have been produced and used under a wide variety of protocols and procedures without standardized methods or documentation. The benefits of a passive sampler, especially for metals analysis, is the sediment remains undisturbed and no oxygen is added to the sample by doing so, thus minimally impacting the redox sensitive analytes however, there is still a lot of uncertainty with regards to the impact oxygen has on these samplers. Deoxygenation is a costly addition in terms of the prep work it requires to keep peepers deoxygenated prior to field deployment and during processing post retrieval. We set out to conduct multiple experiments to determine the impact oxygen as at various stages during the production, deployment, retrieval and processing by designing tests to measure the potential critical points for oxygen contamination during pre and post deployment phases. These experiments included looking into the necessity for deoxygenation pre-deployment, the shelf life of peeper samplers, and samples (post retrieval). Lab scale study results show that oxygenation contamination occurs as quickly as hypothesized, however, the need for deoxygenation of the peeper solution may not be necessary. Our studies show that, when left in air, peepers only stay deoxygenated for less than 30 minutes. However, the metals data correlated well with samplers that were kept deoxygenated during deployment 28000 µg/L, compared to the oxygenated sampler 26000 µg/L, showing less than ten percent difference. These experiments answered a lot of the questions within literature about deoxygenation of peepers.

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