Project Summary (2020-2025)

There is strong evidence that environmentally persistent free radicals (EPFRs) associated with particulate matter (PM) and soils found in/around declared and potential Superfund sites pose adverse health effects. Mitigation of the associated environmental risks requires a detailed understanding of EPFR-contaminated air and soil systems. Specifically, this project is in direct alignment with SRP Mandate 4 – elucidating chemical and physical methods to reduce the amount and toxicity of these hazardous substances. This project studies the microscopic, or atomistic, properties of EPFR formation, including their remarkable stability in the environment, and models the resulting influences of chemical decay on a broad base of metal oxide (MO) platforms. Employing a toolbox of state-of-the-art experimental and molecular ab initio computational methods across differing material platforms (surfaces, nanoclusters/powders, clays, EPA fly ash, soil), the researchers' continued focus is on elucidating individual details of and corresponding local effects (electronic/chemical/atomic structure) on organic molecular-metal oxide/center chemisorption, ensuing charge transfer (redox), and consequent chemical degradation pertinent to EPFR-containing systems such as PM, powders, clays, and real-world (field EPFR) materials. The researchers' aims focus on answering three simple questions at an atomistic level:

1. How do EPFRs chemically form?
2. What causes EPFR decay?
3. Why are EPFR properties similar across differing platforms?

While the researchers' previous efforts have elucidated trends in EPFR formation, the connection between EPFR decay mechanisms, lifetimes, and dependence on MO — the path to destabilization/remediation (SRP Mandate 4) — has not yet been addressed and is a main goal of their project. Although focused primarily on revealing fundamental environmental science, the project works symbiotically with the Center. By identifying material factors from the other projects and correlating results across differing material platforms, they obtain synergistic/antagonistic tendency parameters for EPFR destabilization/remediation that translate to the other projects and, in turn, initiate and clarify mitigation and remediation strategies. By employing experimental processes that both model and recapitulate real-world exposures, this project provides a picture of the microscopic systems generating the EPFRs and related adsorbate systems but, more importantly, interrogates effects that promote/hinder degradation and the corresponding products that influence and enhance activities across the Center. Integrating closely with and expanded by the "Activation, Sensing, and Prevention of Formation EPFRs in Thermal Treatment of Superfund Wastes" project, this allows the Center to synergistically elucidate the atomic mechanisms of EPFR chemistry in a scalable and predictive manner that contributes to understanding biochemical health effects, mitigation, and remediation of these particle-bound pollutants at Superfund sites.