Passive Sampling of Inorganics Using Peepers

There is currently a lack of user-friendly guidance documentation and detailed case studies on how to successfully prepare, deploy, retrieve, sample and interpret data from passive samplers for inorganics. This project’s overall objective is to enhance the standardization of and confidence in the use of peepers for passive sampling of inorganic constituents such as metals, metalloids, and anions in sediment porewater. To support this goal, four tasks are defined:

1. Preparing a detailed literature review of sediment passive sampling of inorganics to identify past and present best practices for peeper preparation, deployment, retrieval, and data analysis;
2. Optimizing and demonstrating a set of best practices for preparing, deploying, and retrieving peepers through a combination of laboratory experiments and a field demonstration;
3. Preparing a user-friendly guidance document that enables end-users to successfully prepare, deploy, and retrieve peepers and interpret peeper data; and
4. Disseminating results through webinars to end-users (site managers, environmental consultants, and commercial analytical laboratories), including presentation at an appropriate conference, a web-training course, and periodic updates via social media to maximize outreach.

Dialysis samplers, also called peepers, are a type of passive sampler that function by allowing sediment porewater to equilibrate with water contained in a small isolated compartment after insertion of the peeper into sediment. Equilibration occurs over a period of time via passive diffusion through a semi-permeable membrane. Following equilibration with the porewater, the peeper is retrieved, and the liquid is analyzed via standard (i.e., EPA SW-846) methods and reported as a concentration in water that can be easily compared to risk-based criteria in water or used in fate modeling. Peepers have been used for decades; however, due to the lack of standard guidance documents, peeper methods have greatly varied, hindering the use of peepers for regulatory and decision-making purposes. The guidance document and demonstration tests proposed in our project would support critical priorities by: 1) Improving methods for establishing porewater-based sediment management standards, 2) Increasing confidence in sediment cleanup levels, and 3) Demonstration and validation of passive sampling-based cleanup levels.

The information and outreach produced in the proposed effort will provide a framework for the use of peepers for delineating inorganics in sediments, and promote the incorporation of the technology so that better site-specific data can be produced for risk assessments, delineation, development of cleanup levels, and monitoring of remedial effectiveness. The use of robust porewater data in this manner will enable more accurate estimates of contaminant availability and risks while avoiding overly protective and inaccurate predictions made using bulk chemistry data (i.e., total concentrations of inorganics in sediment) and inferior measurements of inorganics in porewater that suffer from artifactual issues and/or higher costs. Streamlined guidance for use of peepers will result in cost savings to DoD by facilitating more efficient sediment monitoring/management approaches, which can save hundreds of thousands to millions of dollars per site. (Anticipated Project Completion - 2023)

Risacher, F.F., H. Schneider, I. Drygiannaki, J. Conder, B.G. Pautler, and A.W. Jackson. 2023.  A Review of Peeper Passive Sampling Approaches to Measure the Availability of Inorganics in Sediment Porewater.  Environmental Pollution, 328:121581. doi.org/10.1016/j.envpol.2023.121581.