Oxidative potential (OP) is increasingly recognized as a more health-relevant metric than particulate matter (PM) mass concentration because of its response to varying chemical compositions. Given the limited research on the OP of complex combustion aerosols, the effects of aging processes on their OP remain underexplored. We used online instruments to track the evolution of OP [via dithiothreitol (DTT) assays] during the aging of wood burning and coal combustion emissions by hydroxyl-radical-driven photooxidation and dark ozonolysis. We observed very substantial increases in the intrinsic OP (OP ) of complex combustion aerosols (e.g., OP up to 100 pmol min μg for OH-aged wood burning emissions) within 1 day of equivalent aging. Further analysis in relation to the degree of oxidation revealed a potential for generalizing the OP of carbonaceous aerosols with average carbon oxidation state values ranging from -1.5 to -0.5 by assuming they have a constant OP value of ∼10 ± 6 pmol min μg. Additionally, we uncovered a strong dependency of OP on both the source/precursor and aging pathway with above ∼-0.5. OH photooxidation was identified as an exceptionally efficient pathway for generating highly oxidized, multifunctionalized, and DTT-active products, particularly from wood burning emissions.

Addressing methane emissions across the liquefied natural gas (LNG) supply chain is key to reducing climate impacts of LNG. Actions to address methane emissions have emphasized the importance of the use of measurement-informed emissions inventories given the systematic underestimation in official greenhouse gas (GHG) emission inventories. Despite significant progress in field measurements of GHG emissions across the natural gas supply chain, no detailed measurements at US liquefaction terminals are publicly available. In this work, we conduct multiscale, periodic measurements of methane and carbon dioxide emissions at two US LNG terminals over a 16-month campaign. We find that methane emission intensity varied from 0.007% to 0.045%, normalized to methane in LNG production. Carbon dioxide emissions accounted for over 95% of total GHG emissions using 100-year global warming potential (GWP) for methane. Thus, contrary to observations across other natural gas supply chain segments, we find that reported GHG emissions intensity closely matches measurement informed GHG emissions intensity of 0.24-0.27 kg COe/kg CH. In the context of developing LNG supply chain emissions intensity, we conclude that the use of the Greenhouse Gas Reporting Program emissions intensity provides reasonably accurate estimates of total GHG emissions at LNG terminals.

Detecting and quantifying tire wear particles (TWPs) in the environment pose a unique environmental challenge due to their chemical complexity. There are emerging concerns around TWPs due to their potential high numbers of particles released, outnumbering microplastics, as well as the leaching of toxic additives such as 6-PPD which has been linked to the death of salmon even when present at very low levels (<0.1 μg/L). Analytical techniques such as pyrolysis gas chromatography mass spectrometry (Py-GC/MS) and thermal extraction-desorption gas chromatography mass spectrometry (TED-GC/MS) have been used but also demonstrate limitations including low sample mass, low sample throughput, and complex characterization and quantification procedures. This work aims to overcome these challenges by developing a new approach which utilizes a coupling between thermogravimetric analysis (TGA) and gas chromatography-mass spectrometry (GC/MS). This work is the first to harness conventional TGA-GC/MS for the analysis of tire rubber, with the detection of additives such as 6-PPD, while also pioneering a novel mode of operation, PyroTGA-GC/MS, using fast heating to enable robust quantitative analysis of TWPs in road dust. The limits of detection and quantification of 0.08/0.16 μg and 0.20/0.40 μg for SBR and PI, respectively, are lower than those achieved using Py-GC/MS and TED-GC/MS for SBR and align with those achieved for PI. This study reveals a clear link between the ratio of PI to SBR and the proportion of heavy goods vehicles. This work solves key issues in tire particle analysis related to sample size and throughput. By overcoming these limitations, we introduce a technique that provides an economically viable solution for large-scale commercial analysis of tire rubber and particles.

Tires are a ubiquitous part of on-road transport systems serving as the critical connecting component at the interface of the motive power and road surface. While tires are essential to automobile function, the wear of tires as a source of particulate air pollution is still poorly understood. The variety of reported emissions found in the secondary literature motivated us to summarize all known mass-based tire wear emission factors for light-duty vehicles in primary research. When excluding road wear and resuspension, mean emissions of 1.1 mg/km/vehicle (median 0.2 mg/km/vehicle) were found for tire wear PM and mean emissions of 2.7 mg/km/vehicle (median 1.1 mg/km/vehicle) when including studies with resuspended tire wear. Notably, these factors are substantially lower than broadly cited and accepted factors in the secondary literature with mean emissions of 6.5 mg/km/vehicle (median 6.1 mg/km/vehicle). As revealed by our analysis, secondary literature reports emission factors systematically higher than those of the primary sources on which they are based. This divergence is due to misunderstandings and misquotations that have been prevalent since the year 1995. Currently accepted mass-based emission factors for directly emitted airborne tire wear particles need revision, including those from the United States Environmental Protection Agency and the European Environment Agency.

Recovery of nitrogen from wastewater presents a unique opportunity to valorize waste and contribute to a more circular nitrogen economy. However, dilute solution separations are challenging for most state-of-the-art separations technologies. This often results in technologies having low concentration factors that result in low-value products (e.g., < 1 wt % N). Here, we demonstrate how a cascading electrodialysis system combined with a hollow fiber membrane contactor (ED+HFMC) system can achieve efficient recovery of ammonia from simulated centralized animal feeding operation (CAFO) wastewater. The integrated system achieved an overall concentration factor of ∼200× (∼40× in ED and ∼5× in HFMC). This resulted in a ∼10 wt % NH -N fertilizer product. The specific energy consumption (SEC) for the three stages of the ED was 1.89-6.14 kWh/kg NH -N, which is lower than that of the Haber-Bosch process (8.9-19.3 kWh/kg N). Operating costs were <$0.90/kg NH -N for each of the electrodialysis stages and NH stripping. This integrated ED+HFMC system holds promise for the recovery of ammonia from dilute feedstreams as the ED+HFMC achieves high concentration factors and has low energy demand.

Fine-mode particulate matter (PM) is a highly detrimental air pollutant, regulated without regard for chemical composition and a chief component of wildfire smoke. As wildfire activity increases with climate change, its growing continental influence necessitates multidisciplinary research to examine smoke's evolving chemical composition far downwind and connect chemical composition-based source apportionment to potential health effects. Leveraging advanced real-time speciated PM measurements, including an aerosol chemical speciation monitor in conjunction with source apportionment and health risk assessments, we quantified the stark pollution enhancements during peak Canadian wildfire smoke transport to New York City over June 6-9, 2023. Interestingly, we also observed lower-intensity, but frequent, multiday wildfire smoke episodes during May-June 2023, which risk exposure misclassification as generic aged organic PM via aerosol mass spectrometry given its extensive chemical transformations during 1 to 6+ days of transport. Total smoke-related organic PM showed significant associations with asthma exacerbations, and estimates of in-lung oxidative stress were enhanced with chemical aging, collectively demonstrating elevated health risks with increasingly frequent smoke episodes. These results show that avoiding underestimated aged biomass burning PM contributions, especially outside of peak episodes, necessitates real-time chemically resolved PM monitoring to enable next-generation health studies, models, and policy under far-reaching wildfire impacts in the 21st century.

Given the severe loss of species richness across diverse ecosystems, there is an urgent need to assess and monitor biodiversity on a global scale. The analysis of environmental DNA (eDNA), referring to any DNA extracted from environmental samples and subsequently sequenced, is a promising method for performing such biodiversity related studies. However, a comprehensive understanding of the factors that drive distinct eDNA degradation rates under different environmental conditions is currently missing, which limits the spatiotemporal interpretations that are possible from the eDNA-based detection of species. Here, we explore what role photochemistry may play in the fate of eDNA in aquatic ecosystems. Since few eDNA photodegradation studies have been performed, we extrapolate measured photochemical degradation dynamics from dissolved organic matter (DOM) and cellular DNA to what is expected for eDNA. Our findings show that photochemistry may dominate eDNA degradation under certain environmental conditions (e.g., DOM-rich waters with no light-limitation) and that photochemical alteration of eDNA may impact microbial respiration rates and the quantitative polymerase chain reaction (qPCR)-based detection of eDNA. We therefore encourage future studies to analyze the impact of photochemistry on eDNA degradation and provide suggested research directions that could help improve the accuracy of spatiotemporal inferences from eDNA analyses.

Frequent and severe wildfires have led to increased application of fire suppression products (long-term fire retardants, water enhancers, and Class A foams) in the American West. While fire suppressing products used on wildfires must be approved by the U.S. Forest Service, portions of their formulations are trade secrets. Increased metals content in soils and surface waters at the wildland-urban interface has been observed after wildfires but has primarily been attributed to ash deposition or anthropogenic impact from nearby urban areas. In this study, metal concentrations in several fire suppression products (some approved by the U.S. Forest Service, and some marketed for consumer use) were quantified to evaluate whether these products could contribute to increased metal concentrations observed in the environment postfire. Long-term fire retardants contained concentrations of toxic metals (V, Cr, Mn, Cu, As, Cd, Sb, Ba, Tl, and Pb) 4-2,880 times greater than drinking water regulatory limits, and potentially greater than some aquatic toxicity thresholds when released into the environment. Water enhancers and Class A foams contained some metals, but at lower concentrations than fire retardants. Based on these concentrations and retardant application records, we estimate fire retardant application in the U.S. contributed approximately 380,000 kg of toxic metals to the environment between 2009 and 2021.

Arsenic is a global pollutant. Recent studies found that Fe(II) can oxidize As(III), but the extent of oxidation with mixed-valent iron minerals and the mechanisms involved are unknown. In this study, we investigated whether As(III) can be oxidized under reducing conditions using green rust sulfate (GR-SO), an Fe mineral containing both Fe(II) and Fe(III). Batch sorption experiments showed that GR-SO (1 g L) effectively sorbs environmentally relevant concentrations of As(III) (50-500 μg L) under anoxic, neutral pH conditions with and without citrate (50 μM). X-ray absorption near-edge structure spectroscopy analysis at the As K-edge demonstrated that approximately 76% of As(III) was oxidized to As(V) by GR-SO. Complete oxidation of As(III) was observed in the presence of citrate. As(III) oxidation can be linked to the phase transformation of GR-SO to goethite, resulting in new reactive Fe(III) species that plausibly drive oxidation. Citrate enhanced this process by stabilizing Fe on the mixed GR-SO/goethite surface, preventing its reduction back to Fe(II) and facilitating further As(III) oxidation without significant Fe loss to the solution. This study highlights the cryptic As(III) oxidation that occurs under reducing conditions, providing new insights into the cycling of arsenic in mixed phases of iron-rich, anoxic environments.

Biomass burning (BB) is a major source of aerosols and black carbon, thereby exerting an important impact on climate and air quality. Levoglucosan is the most well-recognized organic marker compound of BB and has been used to quantitatively assess BB's contribution to ambient aerosols. However, little is known about levoglucosan's evaporation under atmospheric conditions, primarily due to the uncertainty of its effective saturation vapor concentration (*) and its unknown activity coefficient (γ), in the complex BB emission matrix. Here, we utilized a thermodenuder to investigate the evaporation of levoglucosan from mixtures with polyethylene glycol (PEG) or BB primary organic aerosol (BBPOA) matrices, respectively. We estimate a pure component log(*/[μg m]) of levoglucosan of 1.1 ± 0.1 at 298 K. We reveal that levoglucosan mixed with PEG or BBPOA becomes more volatile than when treated as a single component due to nonideal molecular interactions. Considering that phase separation might occur in such systems, we term γ apparent activity coefficient (γ ). We estimate log * and γ of levoglucosan in BBPOA of 1.8 ± 0.1 and 3.8 ± 0.3, assuming a liquid phase state. Consequently, γ must be considered to avoid significant underestimation of levoglucosan evaporation via gas-particle partitioning during transport.

Plastics contain various chemical substances, which can impact human and ecosystem health and the transition to a circular economy. Meanwhile, information on the presence of individual substances in plastics is generally not made publicly available, but relies on extensive analytical efforts. Here, we review measurement studies of chemicals in plastics and compile them into a new LitChemPlast database. Over 3500 substances, stemming from all plastic life-cycle stages, have been detected in different plastics in 372 studies. Approximately 75% of them have only been detected in nontargeted workflows, while targeted analyses have focused on limited well-known substances, particularly metal(loid)s, brominated flame retardants, and -phthalates. Some product categories have rarely been studied despite economic importance, e.g., consumer and industrial packaging (other than food packaging), building and construction, and automotive plastics. Likewise, limited studies have investigated recycled plastics, while existing measurements of recycled plastics show higher detection frequencies and median concentrations of regulated brominated flame retardants across many product categories. The LitChemPlast database may be further developed or utilized, e.g., for exposure assessment or substance flow analysis. Nonetheless, the plethora of relevant substances and products underscores the necessity for additional measures to enable the transition to a safe circular plastics economy.

Technoeconomic analysis (TEA) studies are vital for formulating guidelines that drive the commercialization of electrochemical CO reduction (eCOR) technologies. In this review, we first discuss the progress in the field of eCOR processes by providing current state-of-the-art metrices (e.g., faradic efficiency, current density) based on the recent heterogeneous catalysts' discovery, electrolytes, electrolyzers configuration, and electrolysis process designs. Next, we assessed the TEA studies for a wide range of eCOR final products, different modes of eCOR systems/processes, and discussed their relative competitiveness with relevant commercial products. Finally, we discuss challenges and future directions essential for eCOR commercialization by linking suggestions from TEA studies. We believe that this review will catalyze innovation in formulating advanced eCOR strategies to meet the TEA benchmarks for the conversion of CO into valuable chemicals at the industrial scale.

Screening ionic liquids (ILs) with low viscosity, low toxicity, and high CO absorption using machine learning (ML) models is crucial for mitigating global warming. However, when candidate ILs fall into the extrapolation zone of ML models, predictions may become unreliable, leading to poor decision-making. In this study, we introduce a "representation uncertainty" (RU) approach to quantify prediction uncertainty by employing four IL representations: molecular fingerprint, molecular descriptor, molecular image, and molecular graph. We develop four types of ML models based on these representations and calculate RU as the standard deviation of predictions across these models. Compared to traditional model uncertainty (MU), which is based on hyperparameter variations within a single representation, RU outperforms MU in identifying unreliable predictions across four IL property data sets: viscosity, toxicity, refractive index, and CO absorption capacity. Furthermore, we develop ensemble models from the four types of models, which show superior predictive performance compared with that of individual models. Using the RU approach, we screened 1420 ILs and identified 37 promising candidates with low viscosity, low toxicity, and high CO absorption capacity. The predictive performance of our ensemble model, along with the effectiveness of the RU-based approach, was experimentally validated by testing the CO absorption capacity of 14 ILs. This study not only offers a more reliable method for screening and designing ILs, accelerating the discovery process, but also introduces a new perspective on developing ensemble models with enhanced predictive performance.

We propose a method for estimating methane emission durations on oil and gas sites, referred to as the Probabilistic Duration Model (PDM), that uses concentration data from continuous monitoring systems (CMS). The PDM probabilistically addresses a key limitation of CMS: nondetect times, or the times when wind blows emitted methane away from the CMS sensors (resulting in no detections). Output from the PDM can be used to bound the duration of emissions detected by survey-based technologies, such as plane or satellites, that have limited ability to characterize durations due to the typically low temporal frequency (e.g., quarterly) at which they observe a given source. Linear regression indicates that the PDM has a bias of -4.9% (R = 0.80) when evaluated on blinded controlled releases at the Methane Emissions Technology Evaluation Center (METEC), with 86.8% of estimates within a factor of 2× error from the true duration. We apply the PDM to a typical production site in the Appalachian Basin and use it to bound the duration of survey-based measurements. We find that failing to account for CMS nondetect times results in underestimated emission durations of up to a factor of 65× (6400%) on this site.

Increasing pressures on traditional sources of water have accelerated the adoption of water reuse throughout the world. A key consideration for communities pursuing water reuse is understanding the amount of treatment that is needed to ensure adequate human health protection. Several U.S. EPA documents describe the importance of managing acute microbial risks and highlight the utility of quantitative microbial risk assessment for developing "fit-for-purpose" treatment targets based on the source of water and end-use. However, there are no U.S. federal water reuse regulations and states are currently considering microbial treatment targets for various applications. Previous publications have yet to address this need by using an updated and consistent set of input parameters to present risk-based microbial treatment targets across a wide range of sources of water, end-use applications, and health benchmarks. This work combines the most current modeling inputs and dose-response parameter values to provide probability of infection and disease burden-based microbial treatment targets for untreated municipal wastewater, untreated onsite wastewater, graywater, stormwater, and roof runoff water used for potable reuse, indoor nonpotable use, and landscape irrigation applications.

Understanding historical chemical usage is crucial for assessing current and past impacts on human health and the environment and for informing future regulatory decisions. However, past monitoring data are often limited in scope and number of chemicals, while suitable sample types are not always available for remeasurement. Data-driven cheminformatics methods for patent and literature data offer several opportunities to fill this gap. The were developed as an interactive, open source tool for visualizing patent and literature trends over time, inspired by the global warming and biodiversity stripes. This paper details the underlying code and data sets behind the visualization, with a major focus on the patent data sourced from PubChem, including patent origins, uses, and countries. Overall trends and specific examples are investigated in greater detail to explore both the promise and caveats that such data offer in assessing the trends and patterns of chemical patents over time and across different geographic regions. Despite a number of potential artifacts associated with patent data extraction, the integration of cheminformatics, statistical analysis, and data visualization tools can help generate valuable insights that can both illuminate the chemical past and potentially serve toward an early warning system for the future.

Personal care products (PCPs) contain diverse volatile organic compounds (VOCs) and routine use of PCPs indoors has important implications for indoor air quality and human chemical exposures. This chamber study deployed aerosol instrumentation and two online mass spectrometers to quantify VOC emissions from the indoor use of five fragranced PCPs and examined the formation of gas-phase oxidation products and particles upon ozone-initiated oxidation of reactive VOCs. The tested PCPs include a perfume, a roll-on deodorant, a body spray, a hair spray, and a hand lotion. Indoor use of these PCPs emitted over 200 VOCs and resulted in indoor VOC mixing ratios of several parts per million. The VOC emission factors for the PCPs varied from 2 to 964 mg g. We identified strong emissions of terpenes and their derivatives, which are likely used as fragrant additives in the PCPs. When using the PCPs in the presence of indoor ozone, these reactive VOCs underwent oxidation reactions to form a variety of gas-phase oxidized vapors and led to rapid new particle formation (NPF) events with particle growth rates up to ten times higher than outdoor atmospheric NPF events. The resulting ultrafine particle concentrations reach ∼34000 to ∼200000 cm during the NPF events.

Advancements within fecal source tracking (FST) studies are complicated by a lack of knowledge regarding the genetic content and distribution of fecally shed microbial populations. To address this gap, we performed a systematic literature review and curated a large collection of genomes (n = 26,018) representing fecally shed prokaryotic species across broad and narrow source categories commonly implicated in FST studies of recreational waters (i.e., cats, dogs, cows, seagulls, chickens, pigs, birds, ruminants, human feces, and wastewater). We find that across these sources the total number of prokaryotic genomes recovered from materials meeting our initial inclusion criteria varied substantially across fecal sources: from none in seagulls to 9,085 in pigs. We examined genome sequences recovered from these metagenomic and isolation-based studies extensively via comparative genomic approaches to characterize trends across source categories and produce a finalized genome database for each source category which is available online (n = 12,730). On average, 81% of the genomes representing species-level populations occur only within a single source. Using fecal slurries to test the performance of each source database, we report read capture rates that vary with fecal source alpha diversity and database size. We expect this resource to be useful to FST-related objectives, One Health research, and sanitation efforts globally.

Chemical transformation of 2-methyltetrol sulfates (2-MTS), key isoprene-derived secondary organic aerosol (SOA) constituents, through heterogeneous hydroxyl radical (OH) oxidation can result in the formation of previously unidentified atmospheric organosulfates (OSs). However, detected OSs cannot fully account for the sulfur content released from reacted 2-MTS, indicating the existence of sulfur in forms other than OSs such as inorganic sulfates. This work investigated the formation of inorganic sulfates through heterogeneous OH oxidation of 2-MTS aerosols. Remarkably, high yields of inorganic sulfates, defined as the moles of inorganic sulfates produced per mole of reacted 2-MTS, were observed in the range from 0.48 ± 0.07 to 0.68 ± 0.07. These could be explained by the production of sulfate (SO ) and sulfite (SO ) radicals through the cleavage of C-O(S) and (C)O-S bonds, followed by aerosol-phase reactions. Additionally, nonsulfated products resulting from bond cleavage were likely volatile and evaporated into the gas phase, as evidenced by the observed aerosol mass loss (≤25%) and concurrent size reduction upon oxidation. This investigation highlights the significant transformation of sulfur from its organic to inorganic forms during the heterogeneous oxidation of 2-MTS aerosols, potentially influencing the physicochemical properties and environmental impacts of isoprene-derived SOAs.

A February 3, 2023 train derailment and subsequent burn released hazardous chemicals into East Palestine, Ohio. One potential exposure was polychlorinated dibenzo-p-dioxins, dibenzofurans, and coplanar polychlorinated biphenyls (cPCBs), collectively referred to as dioxins. Many studies have linked dioxins to numerous health effects. A pilot study was conducted July 17-18, 2023 to assess residents' serum dioxin levels. Eighteen persons who were White, nonsmokers with a mean age of 55, and 56% female, provided serum for analysis. Measurement of 20 dioxins, furans, and cPCBs congeners was conducted using gas chromatography, isotope dilution, and high-resolution mass spectrometry. A toxic equivalency (TEQ) value for each participant was calculated by multiplying the reported concentration of each congener by its toxic equivalency factor and summing the results. TEQs were compared to 2011-2012 National Health and Nutrition Examination Survey (NHANES) data by race/ethnicity, sex, and age group. All participants had serum TEQ values either below or within the range of NHANES values. Mean TEQ values were lower in younger age groups; we observed no sex-specific differences. These pilot data demonstrate that although dioxins may have formed during the derailment, exposures to participants did not increase their TEQ values compared with 2011-2012 NHANES.

There is a growing awareness of the health impacts of ethylene oxide (EtO) and its role as a carcinogenic and mutagenic air contaminant of concern. Given the need to better understand EtO emissions and associated health effects, it is imperative to overcome the significant challenges associated with EtO measurement in complex air matrices, such as combustion emissions. This work focused on addressing these challenges by evaluating the utility of widely used canister-based EtO ambient measurement approaches, EPA Methods TO-15 and TO-15A, to investigate the presence of EtO in heavy-duty diesel vehicle (HDDV) exhaust. Chassis dynamometer testing was performed on two HDDVs and emissions samples were collected and analyzed following TO-15/TO-15A. Initial testing utilizing TO-15 led to the identification of a diesel exhaust constituent, ethyl nitrite, that coeluted with EtO during analysis and contributed large positive bias. An optimized TO-15A analytical approach was developed and utilized to measure EtO in diesel exhaust from two HDDVs in additional dynamometer tests. Using this optimized approach, EtO was not detected in HDDV exhaust in these tests. This work highlights the importance of utilizing this optimized approach to accurately quantify EtO in mobile source exhaust and may also be needed for testing other combustion sources.