Myron L. Lard

Environmentally persistent free radicals (EPFRs) have emerged as newly identified air pollutants, contributing to various environmental and health concerns. Consequently, the mitigation process, involving the prevention of their formation or acceleration of their decay, is pivotal in reducing the environmental risks associated with EPFRs. This study focuses on the mitigating effect of urea on the generation of EPFRs from 2-monochlorophenol (MCP) at 230 °C thermal remediation under laboratory conditions, abbreviated as MCP230 EPFRs. A strong inhibition of MCP230 EPFR formation was observed, increasing with the addition of urea to 10 wt % relative to the mass of 5% CuO/SiO₂ particles prior to exposure. Loss of activity of Cu²⁺ toward EPFR formation in the presence of urea is likely due to the complexation of Cu²⁺ by urea or by ammonia, one of the major decomposition products of urea. Formation of this complex prevents the adsorption of EPFR precursor molecules on the surface-bound OH groups. It has also been observed that adding solid urea or a urea water solution accelerates the degradation of pre-existing EPFRs within the CuO/SiO₂ solid matrix. In other words, a 1/e lifetime of MCP230 EPFRs from standard exposure was 42 h in a vacuum, while it decreased to 26 and 3 h when 5 and 10% urea were added, respectively, indicating that urea may reduce the stability of EPFRs. This hypothesis is also supported by characterization with X-ray spectroscopies. Our results suggest that urea possesses enormous potential for use as a mitigation agent for the prevention of EPFR formation and the acceleration of decay of existing EPFRs.

Changes in soil microbiome near a thermal treatment facility, together with spatial variation in EPFR g -factor values, indicate higher oxygen-centered radicals near the source. Microcosm experiments show radicals differentially affect soil microbes.

The Norfolk Southern train derailment on February 3, 2023, in East Palestine, Ohio, prompted concerns about the health impacts from the chemical spills and open-air combustion. We hypothesize that the combustion of chemicals, including vinyl chloride, in the presence of transition-metal oxides from the train, tracks, and soil minerals were conducive to the formation of hazardous byproducts including environmentally persistent free radicals (EPFRs), dioxins, and furans. We also hypothesize that these harmful byproducts of combustion have a shared origin and thus will have elevated concentrations in soil samples collected close to the derailment site when compared to concentrations in background soils. This study examined the co-occurrence of these soil contaminants from samples collected August 14–17, 2023, within a two-mile radius of the incident site to assess the concentration of EPFRs, dioxins, and furans. We measured elevated levels of EPFRs (average: 3.00 × 10¹⁷ spins per g) and dioxin/furan toxic equivalence (TEQ) (average: 32.8 pg g⁻¹) near the derailment area compared to background levels (EPFRs: 1.33 × 10¹⁷ spins per g; TEQ: 10.7 pg g⁻¹). Significant positive correlations (p < 0.002) between EPFRs and specific dioxin/furan congener concentrations (0.63–0.74) indicated robust associations between EPFRs and dioxin/furan congeners, the first such observations in field-collected soil samples. These results highlight the environmental health impact of the derailment and associated combustion, underscoring the need for comprehensive longitudinal monitoring and remediation efforts in the affected area and similar industrial accident sites. This study also offers insights into the formation mechanisms and persistence of EPFRs, dioxins, and furans.

Wildfires significantly alter watershed functions, particularly the mobilization of organic carbon (OC). This study investigated OC mobility and the physicochemical characteristics of wildfire-impacted soils and ashes from the northern California and Nevada fires (Dixie, Beckworth, Caldor). Organic carbon in wildfire-derived ashes (9.2–57.3 mg/g) generally exceeded levels in the background soils (4.3–24.4 mg/g), except at the Dixie fire sites. The mobile OC fraction varied from 0.0093 to 0.029 in ashes and 0.010 to 0.065 in soils, though no consistent trend was observed between the ashes and soils. Notably, the ash samples displayed lower OC mobility compared with the soils beneath them. A negative correlation was found between the mobile OC fraction and bulk OC content. Wildfire increased the total amount of mobile OC substantially by 5.2–574% compared to the background soils. Electron paramagnetic resonance (EPR) spectra confirmed the presence of environmentally persistent free radicals (EPFRs), which correlated with observed redox reactivity. Additionally, X-ray absorption near edge structure (XANES) and X-ray fluorescence (XRF) imaging revealed that Fe(II) oxidation in soils beneath the ashes may have enhanced the OC mobility, likely driven by pyrogenic carbon and free radicals. These findings enhance our understanding of post-wildfire OC mobilization and the impact of ash–soil physicochemical properties on watershed health.