Cover Caption: The cover image is based on the Research Article Application of PFAS-mobile lab to support adaptive characterization and flux-based conceptual site models at AFFF releases by Joseph Quinnan et al., https://doi.org/10.1002/rem.21680.

This article presents two aspects of an Environmental Security Technology Certification Program (ESTCP) demonstration conducted at Camp Grayling Army Airfield in Grayling, Michigan: verification of an accelerated per- and polyfluoroalkyl substances (PFAS) screening method using liquid chromatography and tandem mass spectroscopy and its application to develop a flux-based conceptual model. The ESTCP project information can be found here: https://serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER19-5203. The final report is expected to be published by the end of March. The objective is to demonstrate the value of adaptive high-resolution PFAS site characterization using a quantitative screening method that is selective for PFAS compounds and sensitive across the range of concentrations between screening levels at 40 nanograms per liter and source impacts within the milligram per liter range. The reliability of the method is demonstrated using three metrics: sample pair comparability statistics with an Environmental Laboratory Accreditation Program-certified lab, visual interpretation of characterization and relative flux, and comparison of contaminant mass discharge calculated at flux transects. In addition, the study measured vadose zone source strength using three methods: soil to groundwater concentration ratios, lysimeter porewater sample analysis, and synthetic precipitation leaching procedure testing. The overall results demonstrate that application of the mobile lab and the stratigraphic flux approach can distinguish individual PFAS sources, visually map perfluorooctanoic acid and perfluorooctane sulfonate and migration pathways, and provide an efficient means of ranking source contributions to plumes.

Groundwater Monitoring & RemediationVolume 41, Issue 4 p. 13-21 Columns Mass Flux Strategies 20 Years On—Getting the Sand Out of the Gears John Horst, Corresponding Author John Horst john.horst@arcadis.com Search for more papers by this authorMatthew Schnobrich, Matthew SchnobrichSearch for more papers by this authorCraig Divine, Craig DivineSearch for more papers by this authorPatrick Curry, Patrick CurrySearch for more papers by this authorShawn Sager, Shawn SagerSearch for more papers by this authorAllan Horneman, Allan HornemanSearch for more papers by this author John Horst, Corresponding Author John Horst john.horst@arcadis.com Search for more papers by this authorMatthew Schnobrich, Matthew SchnobrichSearch for more papers by this authorCraig Divine, Craig DivineSearch for more papers by this authorPatrick Curry, Patrick CurrySearch for more papers by this authorShawn Sager, Shawn SagerSearch for more papers by this authorAllan Horneman, Allan HornemanSearch for more papers by this author First published: 28 October 2021 https://doi.org/10.1111/gwmr.12491Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume41, Issue4Fall 2021Pages 13-21 RelatedInformation

Experience with groundwater remediation over several decades has demonstrated that successful outcomes depend on quantitative conceptual site models (CSMs). Over the last 30 years, we have progressed from groundwater pump-and-treat remedies, which were largely designed based on a water supply perspective, to in situ and combined remedy strategies, which are only beginning to benefit from understanding the aquifer architecture and distribution of contaminant mass to assess plume maturity, mass flux, and more reliable means of fate and transport assessment. The U.S. Air Force funded the development of the Stratigraphic Flux approach to provide a framework for understanding contaminant transport pathways at its complex sites and enable more reliable and cost-effective remediation. Stratigraphic Flux enables the development of quantitative, flux-based CSMs that are founded in sequence stratigraphy, and high-resolution hydraulic conductivity and contaminant distribution measurements. The result is a three-dimensional graphical mapping of relative contaminant flux and classification of transport potential that is easy for all stakeholders to understand. The Stratigraphic Flux graphical model is based on a hydrofacies classification system that describes transport potential in three segments of the aquifer: transport zones-where the majority of groundwater flow occurs and transport rates are measured in feet per day; slow advection zones-where transport rates are measured in feet per year; and storage zones-where typically less than 1% of flow occurs, and diffusion dominates contaminant transport. The hydrofacies architectures are based on stratigraphy and transport potential is defined by grouping facies by orders of magnitude classes in hydraulic conductivity. By combining the hydrofacies architecture with contaminant concentration distributions, one can map relative contaminant flux to define and target the complex pathways that control contaminant transport and cleanup behavior. In this article, we describe the Stratigraphic Flux framework, focusing on the key information needed and the methods of analysis. We illustrate the results of its application to evaluate migration pathways for trichlorethylene and chromium at a former chrome pit at Air Force Plant 4 in Fort Worth, Texas. A comprehensive guidance document that describes the approach with a broad spectrum of tools and several site examples can be requested from the authors.

Smart characterization approaches apply the latest high‐resolution site characterization methods to find the contaminant mass flux, by integrating relative permeability mapping, classical hydrostratigraphy interpretation, and high‐density groundwater and saturated soil sampling. The key factor that makes Smart characterization different is the application of quantitative saturated soil sampling in less permeable slow advection and storage zones to diagnose plume maturity and understand its implications for remedy selection and performance. Because direct sensing tools like the membrane interface probe are capable of providing screening‐level assessments for hydrocarbons and chlorinated solvents in storage zones, but not 1,4‐dioxane, the recommended Smart approach involves application of specialized high‐capacity mobile laboratories or rapid turn‐around using fixed commercial labs. In addition to the benefit of rapidly characterizing sites, Smart characterization facilitates a flux‐based conceptual site model, which allows stakeholders to focus remedies on the mobile portion of the contaminant mass or, in effect, the mass that matters. Through systematic planning and implementation, predesign characterization can be completed to optimize source and plume remedy strategies, balancing investment in Smart characterization with reductions in total life‐cycle costs to ensure that an appropriate return on investigation is obtained. © 2016 Wiley Periodicals, Inc.