ACS ES&T Air最新文献

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.

In this study, we assessed the performance of PurpleAir PM_2.5 sensors and developed calibration models in Dhaka, Bangladesh─one of the global hotspots most severely affected by extreme air pollution. We collocated an array of PurpleAir (PA-II-SD) sensors alongside a beta attenuation monitor (BAM: MetOne BAM-1020) across the dry and wet seasons. Specifically, we collocated 10 sensors during the wet season and 20 sensors during the dry season, collecting one month of colocation data per season, covering a wide range of pollution levels and meteorological conditions. Quality-assured hourly concentrations from different PurpleAir units have shown good consistency, with pairwise R² values generally exceeding 0.95. We developed empirical correction models by testing 29 multiple linear regression (MLR) forms and Random Forest models. Results showed that for hourly average PM_2.5 concentrations measured by PurpleAir, a simple linear correction model achieved an accuracy (nRMSE) within 17–18% of hourly BAM measurements. More complex MLR models incorporating several meteorological variables and interaction terms improved accuracy (nRMSE) slightly, to ∼15%. Random Forest models slightly outperformed all MLR models, at 12–14% (nRMSE) accuracy relative to BAM. Our findings highlight that existing correction models─particularly those developed for U.S. cities and used in the PurpleAir map─are inadequate for Bangladeshi conditions. Uncorrected PurpleAir cf_atm PM_2.5 data yielded accuracy within 25% of BAM measurements. Further research is needed to assess sensor performance in rural and suburban environments and to evaluate long-term performance under diverse climatological and source conditions in Bangladesh and South Asia.

This study presents the first multiyear investigation of per- and polyfluoroalkyl substances (PFAS) in the atmosphere over the Great Lakes. The levels of ∑PFAS exhibit a broad range from 2.9 to 280 pg/m³. Higher concentrations of PFAS at the urban-influenced site compared to the rural site signified spatial variability between the two sampling locations. Despite the absence of a consistent seasonal pattern, concentrations of perfluorooctanoic acid (PFOA) and neutral PFAS (nPFAS) tend to be higher during the summer months. This pattern appears to be influenced by the seasonal variations of air back trajectories and potential influences from south of the sampling site. The study elucidates potential shifts in atmospheric PFAS dynamics during the COVID-19 pandemic. Applying a modified model with a probabilistic approach, we investigated the transport and fate of PFOA and perfluorooctanesulfonic acid (PFOS) within Lake Ontario. The estimated loadings of PFOA and PFOS from air-to-water were 9.5 ± 3.6 and 17 ± 6.6 kg/y, respectively, close to the values from wet deposition (10 ± 3.9 and 31 ± 12 kg/y, respectively) but much lower than those from inflow and all other sources. The primary output pathways for PFOA and PFOS were from water outflow.

PFAS in the Great Lakes’ atmosphere reveal various spatial and seasonal variability impacted by potential sources and COVID-19, with fate modeling underscoring unaccounted for PFOA inputs to Lake Ontario.

Free amino acids (FAAs) are crucial components of organic nitrogen (ON) in aerosols. We investigated the characteristics of FAAs in PM_2.5 in a cruise campaign from the South China Sea (SCS) to the Eastern Indian Ocean (EIO). The contribution of marine and continental sources to FAAs was assessed in both the continent-surrounded sea area and the open-sea area. Higher total FAA concentrations were observed in the continental-influenced samples than in the oceanic-influenced samples. Among the FAAs, the abundance of Glycine (Gly) was significantly enhanced (71.5%) due to the transport of continental air masses. Moreover, the d/l-aspartate acid ratio exhibited an elevation under the impact of biomass burning. Under marine influence, the abundance of l-tryptophan (l-Trp) increased by 94.8% in the EIO. We propose that Gly and l-Trp can serve as the indicators for continental and marine sources, respectively, and we applied the l-Trp/Gly ratio to quantify their relative contributions to FAAs in marine aerosols. The results reveal the impact of continental transport and marine emissions on atmospheric ON. This study deepens the understanding of features of the nitrogen cycle and its implications for biogeochemical cycling over the ocean.

Particulate 2-methyltetrols (2-MT), 2-methylglyceric acid (2-MG), and C₅-alkene triols serve as critical tracers for identifying isoprene-derived secondary organic aerosols (SOAs). Field observations have identified significant concentrations of C₅-alkene triols, yet no air quality models currently account for the formation pathways of these compounds. Simultaneously, the 2-MT concentrations are usually overestimated by 4–5 times compared to field observations due to the lack of the C₅-alkene triols formation pathway. In this study, we expanded the isoprene-SOA scheme and implemented it into the Community Multiscale Air Quality (CMAQ) model with the latest Community Regional Atmospheric Chemistry Multiphase Mechanism version 2 (CRACMM2) mechanism. The missing formation of C₅-alkene triols via the low NO_x isoprene epoxydiols (IEPOX) pathway, the gas-particle partitioning of isoprene-derived SOA tracers, and the high NO_x SOA formation pathway are comprehensively considered in this expanded isoprene-SOA scheme. Results indicate that the C₅-alkene triols contribute to 68% of all isoprene-derived SOA tracers, with approximately 50% in the gas phase and the remainder in the particle phase. The 2-MT concentrations are better represented in the new scheme compared to the default CRACMM2 based on the field observations. The overall SOA is improved by 0–4 μg/m³ in China with the expanded scheme. The isoprene-derived SOA is highly influenced by anthropogenic emissions, especially SO_x (SO₂ + SO₄^2–), and the reduction in SO_x reduces both isoprene aerosol tracers and organosulfates significantly, while a similar reduction in NO_x leads to small increases in these species for both particle and gas phases.

Measurements of ambient ethane concentrations at a regional air quality monitor in the Eagle Ford oil and gas production region are compared to concentrations predicted using site-level hydrocarbon emission inventories coupled with a Gaussian puff dispersion model (CALPUFF). To account for more than half of mean concentrations due to routine emissions, sites at distances 20–50 km from the receptor site were included in the simulations. Nearly all of the highest observed concentrations were observed at night. For each night in the simulation, the location and magnitude of the maximum predicted concentration and maximum observed concentration were compared, and approximately two-thirds of the highest observed nighttime maximum concentrations were accounted for by routine emissions. In contrast, approximately a third of the highest daytime maxima could be accounted for by routine emissions. Most of the large observed maxima that are attributable to routine emissions are predicted to be caused by sources that were within 10 km of the receptor site, but sources up to 20 or more kilometers from the receptor also contributed to the predicted concentrations. A case study is provided demonstrating the potential of coupling site-level inventories of routine emissions with dispersion modeling for attributing sources of elevated hydrocarbon concentrations.

The largest hydrocarbon enhancements observed at regional monitors are due to both routine emissions and emission events from nearby and distant sources.

The reaction mechanisms and rate constants for the aqueous phase reactions of atmospherically relevant carbonyl organonitrates (ONs) and organosulfates (OSs) were determined via bulk kinetics experiments using nuclear magnetic resonance (NMR) spectroscopy. The OSs and the nonalpha carbonyl substituted ONs were found to exclusively undergo a hydrolysis mechanism which is like that previously found for monofunctional and alpha hydroxy substituted ONs and OSs. However, the nonalpha carbonyl-substituted ONs were also found to undergo hydrolysis via sulfate catalysis (in addition to the previously found Brønsted acid catalyzed pathway), which has not been previously reported for any ONs. The alpha carbonyl-substituted ONs were found to react predominantly according to the E_CO2 mechanism (via both Brønsted acid and sulfate catalyzed pathways) which has also not been previously reported for any atmospherically relevant ONs. Because the E_CO2 mechanism leads to alpha-substituted dicarbonyl compounds, this process could be a precursor to accretion reactions which are needed to explain low volatility ambient secondary organic aerosol (SOA). The kinetics data indicate that the Brønsted acid catalyzed pathways could be relevant for SOA with pH < 1, while the sulfate catalyzed pathways are predicted to be relevant for SOA well below efflorescence point for (NH₄)₂SO₄.