ACS ES&T Air最新文献

Emissions from volatile chemical products (VCPs) have become increasingly important to anthropogenic organic carbon emissions and consequently to anthropogenic ozone and secondary organic aerosol (SOA), as emission control strategies have reduced contributions from combustion sources. Industrial and consumer printing inks contribute considerably to VCP emissions, yet emission speciation profiles for printing inks are outdated and ignore the increasing market share of water-based inks. This study develops organic compound emissions profiles for one organic-solvent-based industrial ink and two water-based consumer inks using microchamber emissions tests. The composition of the solvent-based ink differed from the declared composition. Emission profiles were applied to estimates of SOA and O₃ formation potential and inhalation risk. The chemical species that drive the estimated O₃ formation potential correspond closely to species that drive the total emissions mass. However, this study shows that species responsible for SOA and chronic inhalation risk are present in low quantities in inks, and those end points may be under-emphasized in mass-weight emission profiles. The SOA and O₃ formation from printing inks is estimated to have decreased about 42% since 2001, principally due to decreasing total ink usage but aided by increased use of water-based inks, which have a low potential to form SOA and O₃.

The interaction of organic aerosols with water vapor plays a crucial role in cloud processes but is still challenging to fully elucidate due to its complexity. Recently, we developed a water uptake methodology for particles collected on Teflon filters, enabling the quantification of both chemical composition and hygroscopicity of the same sample. In this study, the hygroscopicity of organic compounds with varying functionalities collected on Teflon filters was quantified, including dicarboxylic acids (malonic, glutaric, succinic), multifunctional dicarboxylic acids (tartaric, citric), sugars (glucose, levoglucosan), and a polyol (meso-erythritol) at three relative humidities (RHs: ≈84%, 90%, and 97%). The hygroscopicity parameter (κ) was derived and compared to previous studies. A regression model was developed that predicts κ as a function of physicochemical properties (O/C ratio, number of carbons, and ring oxygen (O*)), which may facilitate the use of Fourier-transform infrared (FTIR) spectroscopy to predict hygroscopicity in ambient samples.

Aerosols influence Earth’s energy balance and hydrological cycle as cloud condensation nuclei (CCN), yet uncertainties persist in how anthropogenic emissions alter their abundance and climate-relevant properties. Abrupt, large-scale reductions in human activities provided a natural experiment to quantify anthropogenic impact on aerosol-cloud-climate interactions in coastal India. Combining chemical and microphysical measurements under drastically reduced and subsequently reintroduced emission scenarios, we reveal that CCN concentrations increased by 80–250% postlockdown. This surge coincided with increased new particle formation (NPF) event frequency and enhanced particle growth rates. Postlockdown air masses shifted from marine to continental sources, revealing that anthropogenic organic matter (OM), despite lower hygroscopicity, dominated particle growth to CCN-active sizes, offsetting hygroscopicity limitations. These findings demonstrate how shifts in anthropogenic activity can strongly impact aerosol–cloud interaction potential, even under varying air mass influences, and provide a reference for understanding the atmospheric effects of future air quality interventions.

Organic-rich aerosols in coastal India show strong sensitivity to changes in anthropogenic emissions and wind patterns, enhancing new particle formation and cloud-forming potential, highlighting implications for air quality interventions.

In this study, a novel screening method was implemented by a local distribution company (LDC) to identify below ground pipeline leaks that have high leak flow rates (≥10 scfh CH₄, 3.19 g/min) for the purpose of prioritizing repairs and reducing methane emissions. This decision tree (DT) method correlates methane concentration measurements as a function of defined ground surface conditions to leak flow rate. Established threshold methane surface concentrations at each defined surface condition category is used to identify leaks with high flow rates. Direct leak flow rate measurements at more than 400 leak sites were used to evaluate the method and determine the frequency of correctly classifying leak rate bins. These data were used in conjunction with annual leak inventory data to provide robust company-specific CH₄ emission factors (C-SEFs) with 90% confidence intervals (CI) of ∼±20%. State-of-the-art statistical analyses, bootstrap resampling, Monte Carlo, and Bayesian probabilistic analyses were used to estimate the DT errors, calculate the C-SEFs and confidence bounds, and estimate annual system emissions with CIs. These C-SEFs explicitly treat the skewed distributions of high flow rate vs low flow rate leaks: 13.3 scfh CH₄ (CI 10.4 to 16.6) for leaks ≥10 scfh CH₄ and 1.82 scfh CH₄ (CI 1.52 to 2.16) for leaks <10 scfh CH₄. Furthermore, these C-SEFs do not depend on classification of pipeline types and avoid issues with assigning a pipeline type for each leak. National methane emission estimates from natural gas distribution systems are outdated and have high uncertainty; however, C-SEFs can solve this problem. For the Southern California Gas Company system, annual leak emissions for 2015, before the method was implemented, were 38.3 Gg CH₄/yr, similar to an estimate using EPA emission factors. More importantly, the postimplementation 2023 emission estimate of 8.98 Gg CH₄/yr (CI 7.33 to 10.8) was 75% less than estimated for 2015. This emission reduction resulted from aggressive improvement in leak management practices implemented since 2015, including increased leak surveys, reduction of leak inventory, and application of the DT method to prioritize high flow leaks for repair.

Secondary organic aerosols (SOA) have complex, multicomponent composition that controls particle viscosity and gas-particle partitioning, key factors to their atmospheric evolution. This study investigates the chemical composition, volatility and viscosity of SOA formed by ozonolysis of cyclic α-pinene (PSOA) and acyclic ocimene (OSOA) monoterpenes. Using Temperature-Programmed Desorption combined with Direct Analysis in Real-Time ionization and High-Resolution Mass Spectrometry, we determined the molecular composition and saturation mass concentration of individual SOA constituents. These data enabled gas-particle partitioning and viscosity estimates under varied atmospheric conditions. PSOA, composed of higher molecular weight and less oxidized species, shows higher condensability and viscosity under high total organic mass (tOM) loadings. In contrast, OSOA, consisting of more oxidized, lower molecular weight species, exhibits greater sensitivity to tOM, with viscosity increasing significantly upon dilution. Poke-flow experiments support this trend, indicating that OSOA undergoes more dynamic compositional and phase changes during atmospheric aging. These observations reveal distinct dynamic trends in the atmospheric transformations and reactivity of SOA from cyclic and acyclic monoterpenes, with the latter showing greater compositional changes during aging that alter viscosity and diffusion. This highlights the importance of incorporating such dynamic transformations into atmospheric models to improve predictions of SOA atmospheric loadings, lifetimes, and impacts.

We report an inventory of nitrogen-containing organic compounds in the Los Angeles Air Basin in late August, 2021. Gas-phase multifunctional nitrogen-containing compounds are measured by chemical ionization mass spectrometry (CIMS) using the CF₃O^– reagent ion both with and without gas chromatography (GC) separation. We use a time-of-flight aerosol mass spectrometer (ToF-AMS) to quantify the abundance of nitrogen-containing organic compounds present on submicron particles. These nitrogen-containing organic compounds comprise a substantial fraction of non-NO_x reactive nitrogen during the day and, together with nitrous acid (HONO), a larger fraction during nighttime. Alkylnitrates produced in the oxidation of biogenically- and anthropogenically derived alkenes dominate the budget, but nitroaromatics also make a significant contribution. The GC–CIMS observations illustrate that the nighttime alkylnitrates are generated via reaction of alkenes with the nitrate radical and that the resulting nitrooxy-peroxy radicals react with both HO₂ to form hydroperoxides and other RO₂ to form primarily nitrooxy carbonyls. Aerosol organic nitrates on PM1.0 make up approximately a quarter of the total organic nitrates during daytime and nearly half at night.

While general monitoring stations provide essential data on criteria air pollutants across a larger area, air quality research supersites offer comprehensive chemical composition measurements, albeit with limited spatial coverage. This study demonstrates the complementary roles of these two types of monitoring. Using data from the Hong Kong air quality monitoring network of 15 stations, we identified 37 city-scale haze episodes between November 2020 and May 2021, defined by PM_2.5 concentrations exceeding 25 μg m^–3. Hourly to bihourly measurements of PM_2.5 chemical compositions─including molecular and elemental tracers─at a supersite enabled PM_2.5 source identification and apportionment. Strong correlations in PM_2.5 and trace element concentrations between the general stations and the supersite indicate spatial homogeneity of air pollution across Hong Kong during these episodes. Variations in the air mass origin and source intensity were found to significantly influence city-scale PM_2.5 levels. Source apportionment based on the tracer measurements revealed dynamic changes in source contributions under different atmospheric conditions. Our findings demonstrate that detailed chemical characterization and source apportionment at a supersite can provide quantitative source insights into city-scale haze events, thus supporting the development of more targeted air pollution control strategies at a city level, such as Hong Kong and similar megacities.

Hourly to bihourly measurements of detailed chemical compositions of PM_2.5 at an air quality research supersite provide quantitative insights into city-scale PM_2.5 pollution sources, supporting improved understanding and management of urban haze events.

Interior paints are a significant source of both volatile and very volatile organic compounds (VOCs and VVOCs, V/VOCs) in a newly painted indoor environment. Natural and artificial light sources such as sunlight and fluorescence light may influence the emissions of V/VOCs from photocatalytic paints. However, the effect of indoor light sources on nonphotocatalytic paint has not been extensively explored. Here, we conducted laboratory simulations of water-based acrylic paint (WBP) and solvent-based nitrocellulose paint (NP) in indoor air and found that total V/VOC concentrations increased under different lighting conditions, with the highest increase under LED lights, followed by fluorescent and ultraviolet (UV) lights. The temperature increased by around 2 °C during illuminations and promoted the release of V/VOCs. However, our predictions of V/VOC emissions with temperature rise suggested that for both WBP and NP, certain VOC species (e.g., toluene) underwent photodegradation simultaneously under fluorescent and UV lights. Secondary formation of formaldehyde was even observed for NP under the influence of fluorescent or UV lights. These laboratory findings were corroborated by investigations in a newly painted environment. The observed effects of indoor lights on V/VOC emissions and consumption from nonphotocatalytic paints enhance our understanding of indoor air quality, especially in newly renovated spaces.

Airborne allergens (aeroallergens) significantly contribute to respiratory allergies and asthma. Traditional methods such as cleaning and allergen avoidance have shown mixed results in improving health outcomes in sensitized individuals, and effective control of airborne protein allergens remains a practical challenge within the built environment. To address this challenge, this study developed a controlled experimental system to generate respirable particles (≤ 10 μm) containing common aeroallergens from mites, pet dander, mold, and pollen, in both dust and purified forms. Allergens were aerosolized into a 10 m³ controlled environment chamber where the contents were either exposed to a calibrated UV₂₂₂ irradiation field or left untreated (control). Respirable aerosols containing allergens were subsequently collected by condensation capture at 10 min intervals over the course of an hour to evaluate allergen stability. Aeroallergens were quantified using an antibody-based immunoassay, which relies on intact protein conformation for antibody-allergen recognition, binding, and quantification. In a time frame relevant to indoor air exchange rates (30 min), statistically significant reductions in airborne allergen levels were observed in response to UV₂₂₂ doses ≤ 16.8 mJ/cm² when compared to otherwise identical control conditions. These results suggest that UV₂₂₂ may be engineered for use as an aeroallergen intervention strategy.

Far UV exposure significantly reduces immune-based detection of airborne allergens within a controlled chamber relevant to the built environment.

The Tibetan Plateau (TP), known as the “Third Pole” of the Earth, exhibits exceptional climate sensitivity, yet the climate and health effects of atmospheric fine particulate matter (PM_2.5)─a significant warming agent─remain poorly characterized in the TP. In this study, we conducted parallel PM_2.5 sampling in the TP (Lhasa and Nyingchi) and Beijing. Comparative analysis revealed that PM_2.5 in the TP shows weaker light absorption but comparable inherent oxidative potential (OP) to urban Beijing, suggesting substantial aerosol toxicity in the pristine TP. This difference can be explained by considering the roles of organic carbon (OC) and metals. PM_2.5 in the TP contains both a greater proportion of OC and a higher degree of aging in its OC fraction, which not only influences light absorption and OP but also magnifies the effect of OC aging on these properties. Notably, in Nyingchi, a relatively pristine high-altitude region, the higher OC content demonstrates stronger OC-correlated light absorption and OP than Lhasa, where transition metals additionally contribute to OP. These findings provide valuable parameters for understanding optical properties and health effects in high-altitude areas, advance the optical–toxicity coupling relationship, and redefine our understanding of air pollution risks in high-altitude environments.