Abstracts

“Developing a Quantitative Framework for Predicting Abiotic Attenuation Under Natural and Transitional Site Management Scenarios” by Dr. Paul Tratnyek (SERDP Project ER20-1357)

Many contaminated groundwater sites are candidates for transition from active remediation to passive remedies (APTs). Such transitions are expected to result in large changes in the in situ chemical and biological conditions that control contaminant fate. This is especially true for abiotic natural attention (ANA), which requires reactive mineral phases that are labile to decay due to aging and other reactions that do not contribute to contaminant reduction. Because these phases are metastable ­­-- and therefore potentially transient, especially during APTs -- we termed them reactive mineral intermediates (RMIs). The main goal of this SERDP project is to explore the hypothesis that RMIs are the phases most responsible for ANA by identifying RMI phases, characterizing the processes that form and decay RMIs, quantifying RMI reactivity with groundwater contaminants, and developing a quantitative framework to incorporate RMIs into conceptual site models. Results to date range from the development of databases for iron mineral thermodynamics and contaminant reduction kinetics, systematic batch experiments on the reactivity of chlorinated ethenes with iron minerals and Fe(II) or S(-II), and large-scale columns tests that simulate chlorinated ethene reduction under (stopped) flow conditions. This presentation summarizes these results and compares them with recent work by others that supports the RMI hypothesis.

“Transitioning from Active Remedies to Monitored Natural Attenuation” by Dr. David Adamson (SERDP Project ER20-1429)

At many DoD sites, the performance of active remedies has appeared to “hit a wall” in decreasing the time to achieve closure, in part due to site heterogeneity and the role of matrix diffusion in enhancing contaminant persistence. These complex sites are prime candidates for a “transition assessment,” where the viability of continuing with an active remedy or implementing other remedies is evaluated relative to less intensive approaches like monitored natural attenuation (MNA). The objective of this project is to provide quantitative tools to help site managers answer specific technical questions that are important during a transition assessment. To accomplish this, a web-based application (Transition Assessment Assistant [TA2]) that combines several key concepts and allows users to perform a site-specific transition assessment was developed. The tool includes modules that estimate rate constants and trends for various monitoring intervals, establish whether performance has become asymptotic, estimate the remedial performance of specific technologies, and provide predictions of cleanup times. By providing a roadmap for evaluating sites where MNA could serve as an effective transition technology, this tool improves the technical basis for decision making to help foster consensus among stakeholders.

Speaker Biographies

Dr. Paul Tratnyek is currently a professor in the School of Public Health at the Oregon Health and Science University in Portland, Oregon. He joined the faculty in the Department of Environmental Science and Engineering at the Oregon Graduate Institute in 1991. There, he became involved in OGI’s Center for Groundwater Research and the University of Waterloo’s Solvents-In-Groundwater Research Consortium. The latter allowed him to become one of the first researchers to focus on zerovalent iron (ZVI) for the remediation of contaminated groundwater. In the 30 years since then, Dr. Tratnyek has published a large body of high-impact research on ZVI, as well as on other aspects of in situ chemical reduction (ISCR) and oxidation (ISCO). This includes some of the earliest work on the abiotic reduction of contaminants, which foreshadowed many of the fundamental aspects of what is now known as abiotic natural attenuation (ANA). This work has targeted chlorinated solvents and explosives, as well as emerging and especially recalcitrant contaminants like 1,2,3-trichloropropane (TCP) and PFAS. Dr. Tratnyek received a bachelor’s degree from Williams College and a doctoral degree in applied chemistry from the Colorado School of Mines.

Dr. David Adamson is a Vice President and Principal Engineer at GSI Environmental. He has more than 22 years of experience with a focus on chemical fate and transport, emerging contaminants, and remediation. Dr. Adamson’s professional experience includes site investigation, characterization, and remediation, with projects in the United States, Europe, Latin America, and the Middle East. These projects involve the design, implementation, and management of full‐scale remediation projects. Dr. Adamson has authored or co‐authored over 60 published technical articles and has served as a principal or co-principal investigator on over 20 DoD-sponsored research projects. He is a coauthor of the DoD‐sponsored guidance document “Frequently Asked Questions About MNA” and was one of three co‐instructors for the DoD sponsored “Massive Open Online Course” (MOOC) on MNA. He has served as a lecturer and adjunct assistant professor at Rice University. Dr. Adamson received a doctoral degree in civil and environmental engineering from the University of Iowa.