ACS ES&T Air最新文献

While the contribution of coal combustion to atmospheric particulate matter is well-recognized, its specific role in winter haze remains insufficiently explored. In this study, we elucidate the quantitative effect of coal combustion on winter haze pollution based on high temporal resolution measurements of trace metals in PM_2.5. We identified arsenic (As) and selenium (Se) as reliable indicators of coal combustion, with their enrichment factors exceeding 10⁴. The significant increase in As and Se concentrations (9.6-fold and 7.1-fold increase) during severe haze episodes underscores the enhanced contribution of coal combustion to winter haze pollution. Chemical mass closure results indicate that primary emissions from coal combustion contribute 15% to PM_2.5, with its proportion in primary PM_2.5 mass reaching 42% and 57% during non-haze and haze episodes, respectively. Simulations utilizing the multiphase chemical model (RACM-CAPRAM) indicate that transition metal-catalyzed oxidation is responsible for 68% of secondary sulfate formation, with the aqueous phase and surface catalysis contributing 59% and 9%, respectively. Excluding coal combustion-emitted SO₂, Mn, and Fe results in a 49% reduction in secondary sulfate production. This research presents a comprehensive assessment of the impact of coal combustion on winter haze in northern China, offering vital insights for formulating effective pollution control strategies in the future.

Motivated by the recent tightening of the US annual standard of fine particulate matter (PM_2.5) concentrations from 12 to 9 μg/m³, there is a need to understand the spatial variation and drivers of historical PM_2.5 reductions. We evaluate and interpret the variability of PM_2.5 reductions across the contiguous US using high-resolution estimates of PM_2.5 and its chemical composition over 1998–2019, inferred from satellite observations, air quality modeling, and ground-based measurements. We separated the 3092 counties into four characteristic regions sorted by PM_2.5 trends. Region 1 (primarily Central Atlantic states, 25.9% population) exhibits the strongest population-weighted annual PM_2.5 reduction (−3.6 ± 0.4%/yr) versus Region 2 (primarily rest of the eastern US, −3.0 ± 0.3%/yr, 39.7% population), Region 3 (primarily western Midwest, −1.9 ± 0.3%/yr, 25.6% population), and Region 4 (primarily the Mountain West, −0.4 ± 0.5%/yr, 8.9% population). Decomposition of these changes by chemical composition elucidates that sulfate exhibits the fastest reductions among all components in 2720 counties (76% of population), mostly over Regions 1–3, with the 1998–2019 mean sulfate mass fraction in PM_2.5 decreasing from Region 1 (29.5%) to Region 4 (11.8%). Complete elimination of the remaining sulfate may be insufficient to meet the new standard for many regions in exceedance. Additional measures are needed to reduce other PM_2.5 sources and components for further progress.

Imidazole produced by the interaction of glyoxal with nitrogen-containing chemicals in atmospheric particles can yield secondary organic aerosol (SOA) due to atmospheric oxidation. However, knowledge about the aqueous phase reaction mechanism of imidazole formation and its oxidation is still very limited. This work investigated the formation mechanism and aqueous-phase oxidative degradation reactions of imidazole with the hydroxyl radical (^•OH), nitrate radical (NO₃^•), and ozone (O₃). Results showed that the formation of imidazole involves many dehydration reactions and is favorable under moderate- or low-RH conditions. The calculated atmospheric lifetimes of 14.05, 0.27, and 3.45 h for reactions with ^•OH, NO₃^•, and O₃, respectively, suggest the efficient oxidation of imidazole under tropospheric aqueous-phase conditions. Formamide and oxamide are the main products in the presence of O₂, and nitro-imidazoles can also be formed in the presence of NO₂. The optical properties of imidazole evolve significantly, attributable to the formation of nitro-imidazoles, resulting in a red shift of absorption peak to the UVA and UVB region.

Formamide and oxamide are the main aqueous oxidation products of imidazole, implying a potentially important source of SOA.

Organophosphate esters (OPEs) are commonly used as plasticizers in nail polish. There is limited research on OPEs release from nail polish into the environment and the associated health risks. This study employed a volatilization simulator, and indoor fugacity modeling (ICECRM) was used to predict OPEs emissions and indoor concentrations from nail polish. The concentrations of 11 OPEs in nail polish ranged from 0.38 to 1254 μg/g, with TPHP accounting for 87% of the total concentration. Following the application of nail polish, the OPEs emission rate was observed to peak at 1320 ng/h after 2 min, decreasing by approximately 62% after 30 min, and by around 77% after 1 h. In comparison to emission rates from other indoor items, nail polish exhibited notably higher emission rates, significantly impacting the indoor environment during daily usage. The ICECRM model outcomes predicted that the total OPE concentration in the air would reach 582 ng/m³, while the concentration would be 148 μg/g in particulate matter and 63.2 μg/g in dust. The health risk assessment suggests a potential increased risk of cancer (10^–5) within the first hour of applying nail polish for nail salon workers. Therefore, this study strongly recommends proper ventilation and prompt cleaning of dust generated during nail polish application.

Since the 1930s, germicidal ultraviolet (GUV) irradiation has been used indoors to prevent the transmission of airborne diseases, such as tuberculosis and measles. Recently, it has received renewed attention due to the COVID-19 pandemic. While GUV radiation has been shown to be effective in inactivating airborne bacteria and viruses, few studies on the impact of GUV on indoor air quality have been published. In this work, we evaluate the effects of GUV222 (GUV at 222 nm) on the chemistry of a common indoor volatile organic compound (VOC), limonene. We found that the production of O₃ by the GUV222 lamps caused the formation of particulate matter (PM) and oxygenated volatile organic compounds (VOCs). We also found that the chemistry proceeds through the ozonolysis of limonene as well as the reaction with secondary OH, and that the presence of GUV light led to observable but small perturbations to this chemistry. Understanding the effects of GUV222 on indoor air quality is important in evaluating the safety of these devices.

Minimal knowledge of the direct impact of germicidal ultraviolet light on indoor air quality exists. This study found it to have a minor influence on aerosol formation from the oxidation of limonene, beyond the impacts on ozone and OH.

Sea salt aerosol is the largest natural aerosol source. The particle number size distribution (PNSD) of sea salt aerosol determines its direct and indirect radiative forcing. The PNSD of sea salt is important in quantifying the contribution of sea salt to marine cloud nuclei population. However, measuring the PNSD of sea salt is challenging, especially for sub-micrometer particles. In this study, we propose an approach to determine the PNSD of sea salt by applying positive matrix factorization (PMF) on ambient particle number size distribution data. Using the bulk PM₁ (particulate matter smaller than 1 μm in diameter) sea salt mass concentration as an external constraint, the PNSD of sea salt can be successfully retrieved. This approach is expected to advance our understanding of the global distribution and climate impact of sea salt aerosol.

This study assesses low-cost sensors (LCS) for the mobile monitoring of air quality, which has thus far been scarcely investigated. NO₂ and PM_2.5 were measured using LCS and higher-grade instruments while driving across various environments in London (943 km) and northern Europe (2923 km), including urban areas, motorways, and tunnels. The data were classified according to the environment where the measurements were carried out, and the performances of LCS and higher-grade instruments were compared. Results indicate that the performances of the sensors were influenced by the rate of change in pollutant concentration in different environments and not by vehicle speed. Excluding tunnel environments, overall, the particulate matter sensors correlated better with their higher-grade instrument than the electrochemical (EC) sensors, with R² values from 0.90–0.96 in the different environments, compared with 0.39–0.72 for the EC sensors. Tunnels presented a unique opportunity to test the time response of the systems, given the rapid change in concentration upon entering, and all sensors showed limited response times. This is the first time that EC NO₂ sensors have been rigorously tested against reference monitors while mobile. Their absolute measurements appear unaffected by movement; however, their time resolution may not be high enough for mobile monitoring in highly variable environments.

Although atmospheric organic pollutants have been extensively studied to elucidate summertime urban photochemical air pollution, uncertainties remain concerning the quality of wintertime air in large northern North American cities. Here, we used online mass spectrometric measurements of volatile organic compounds (VOCs) and organic aerosol (OA), combined with positive matrix factorization (PMF), to identify sources of organic pollutants in downtown Toronto, Canada during February–March 2023. In some cases, comparable PMF factors were identified for both VOCs and OA, such as from traffic, cooking, and background oxygenated sources. However, VOC PMF yielded additional information, such as a factor associated with human-related emissions of VOCs. Additionally, VOC PMF yields two traffic factors: one likely related to gasoline and one to diesel use. Despite cold and relatively dark conditions, the OA and VOC oxygenated factors both grow in intensity during the daytime, indicative of photochemical activity, whereas the traffic and cooking factors were enhanced in the morning and late evening due to the timing of vehicle use, cooking, and boundary layer effects. This study illustrates the benefits that arise from the parallel source–receptor analyses of organic gases and aerosol particles.

Volatile organic compounds (VOCs) are important constituents of indoor and urban air pollution. Emissions into building attics have rarely been studied, resulting in a lack of information about this potentially important air pollution source. VOC transport from residential attics to outdoor air is generally missing from emission inventories. In this study, attic VOC concentrations and emissions were assessed in a normally-occupied single-family residence in Oakland, California over 10 weeks during autumn 2021. A proton-transfer-reaction time-of-flight mass spectrometer was utilized to sequentially measure VOC concentrations in the attic, the living space, and outdoors at a rate of twice per hour. Over 200 VOCs were detected at concentrations averaging above five parts per trillion, including many known to be emitted from building materials and wood decomposition. Inert tracer gases were continuously released at known rates into the attic, living zone, and basement to characterize air change rates and interzonal flows. Combining the measurements in a material-balance model, we determine time-resolved and speciated VOC emission factors into the attic and to outdoors from the attic. We find that furfural is a key indicator species and that large diurnal temperature changes in the attic significantly influence VOC emissions from the attic to outdoors.

Information regarding residential attic VOC composition and emission rates is scarce. This study reports average concentrations and investigates the temperature dependence of direct attic VOC emission rates.

Nitrous acid (HONO) is a key molecule in the reactive nitrogen cycle. However, sources and sinks for HONO are not fully understood. Particulate nitrate photochemistry has been suggested to play a role in the formation of HONO in the marine boundary layer (MBL). Here we investigate the impact of marine relevant organic compounds on HONO formation from aqueous nitrate photochemistry. In particular, steady-state, gas-phase HONO yields were measured from irradiated nitrate solutions at low pH containing marine-dissolved organic matter (m-DOM). m-DOM induces a nonlinear increase in HONO yield across all concentrations compared to that for pure nitrate solutions, with rates of HONO formation increasing by up to 3-fold when m-DOM is present. Furthermore, to understand the potential synergistic effects that may occur within complex samples such as m-DOM, mixtures of chromophoric (light-absorbing) and aliphatic (non-light-absorbing) molecular proxies were utilized. In particular, mixtures of 4-benzoylbenzoic acid (4-BBA) and ethylene glycol (EG) in acidic aqueous solutions containing nitrate showed more HONO upon irradiation compared to solutions containing only one of the molecular proxies. This suggests that synergistic effects in the HONO formation can occur in complex organic samples. Atmospheric implications of the results presented here are discussed.

This study examines how marine-dissolved organic matter enhances the photochemical conversion of nitrate into nitrous acid and uncovers synergistic effects in the formation of nitrous acid in the environment.