Search Results (688)

Oligomerization of glyoxal (GL) and methylglyoxal (MG) plays a vital role in secondary organic aerosol (SOA) formation in aqueous aerosols. However, the influence of emerging contaminants on the oligomerization of GL and MG remains unclear. Therefore, using quantum chemical and kinetic calculations, we investigated the oligomerization of GL and MG in the presence of phthalate esters (PAEs), including dimethyl phthalate (DMP), diethyl phthalate (DEP), dipropyl phthalate (DPP), and dibutyl phthalate (DBP), and the role of PAEs in the oligomerization. Our findings indicate that the direct PAE-mediated oligomerization of GL and MG is hindered due to the lack of reactive sites. However, the oligomerization of GL and MG is readily mediated by the hydrolysates of PAEs, which are the preferred forms of PAEs in weakly acidic aerosols, attributable to the additional -OH groups. The mechanisms show that the indirect PAE-mediated oligomerization proceeds via three-step reactions, including nucleophilic attack on carbenium ions, hydration, and deprotonation, which are thermodynamically and kinetically favorable. Our results reveal that the role of PAEs in the GL/MG oligomerization needs to be emphasized, particularly in conditions with a pH value approaching neutrality. Full article

The vertical profiles of PM_2.5 chemical components are crucial for tracing pollution development, determining causes, and improving air quality. Yet, previous studies only yielded transient and sparse results due to technological limitations. Comprehensive analysis of component vertical distribution across an entire boundary layer remains challenging. Here, we provided a first-ever vertical–temporal continuous dataset of aerosol component concentrations, including sulfate (SO₄²⁻), ammonium (NH₄⁺), nitrate (NO₃⁻), organic matter (OM), and black carbon (BC), using ground-based remote sensing retrieval. The retrieved dataset showed high correlations with in situ chemical observation, with all components exceeding 0.75 and some surpassing 0.90. Using the Beijing 2022 Winter Paralympics as an example, we observed distinct vertical patterns and responses to meteorology and emissions of different components under strictly controlled conditions. During the Paralympics, the emissions contribution (51.12%) surpassed meteorology (48.88%), except SO₄²⁻ and NO₃⁻. Inorganics showed high-altitude transport features, while organics were surface-concentrated, with high-altitude inorganic(organic) concentrations 1.19(0.56) times higher than those near the surface. SO₄²⁻ peaked at 919 m and 1516 m, NH₄⁺ and NO₃⁻ showed an additional peak near 300–500 m, influenced by surface sources and secondary generation. The inorganics exhibited a transport-holding–sinking–resurging process, with NO₃⁻ reaching higher and sinking more. By contrast, organic components massified near 200 m, with a slight increase in high-altitude transport by time. The dispersion of all components driven by a north-westerly wind started 5 h earlier at high altitudes than near the surface, marking the end of the process. The insights gleaned highlight regional inorganic impacts and local organic impacts under the coupling of emission control and meteorology, thus offering helpful guidance for source attribution and targeted control policies. Full article

Air quality simulations were performed for Athens (Greece) in ~1 km resolution applying the models WRF-CAMx for July and December 2019 with the secondary organic aerosol processor (SOAP) and volatility basis set (VBS) organic aerosol (OA) schemes. CAMx results were evaluated against particulate matter (PM) and OA concentrations from the regulatory monitoring network and research monitoring sites (including PM_2.5 low-cost sensors). The repartition of primary OA (POA) and secondary OA (SOA) by CAMx was compared with positive matrix factorization (PMF)-resolved OA components based on aerosol chemical speciation monitor (ACSM) measurements. In July, OA concentrations underestimation was decreased by up to 24% with VBS. In December, VBS introduced small negative biases or resulted in more pronounced (but moderate) underestimations of OA with respect to SOAP. CAMx performance for POA was much better than for SOA, while VBS decreased the overestimation of POA and the underestimation of SOA in both study periods. Despite the SOA concentrations increases by VBS, CAMx still considerably underestimated SOA (e.g., by 65% in July). Better representation of simulated OA concentrations in Athens could benefit by accounting for the missing cooking emissions, by improvements in the biomass burning emissions, or by detailed integration of processes related to OA chemical aging. Full article

Objectives: There is a scarcity of pharmacological treatments that efficiently address lung injury in individuals experiencing acute respiratory distress syndrome (ARDS). Early inhaled corticosteroids and ipratropium may reduce pulmonary inflammation and injury of the lungs, minimizing the risk of ARDS. Method: This is a double-blinded randomized control trial conducted on patients at risk of ARDS. Patients were randomly allocated into two groups; the intervention group (63 patients) were administered aerosolized budesonide and ipratropium bromide, and the control group (56) were administered a placebo every eight hours for five days. Alteration in oxygen saturation divided by inspired oxygen (Fio2) (S/F) after five days was the primary outcome. Secondary outcomes included ARDS occurrence, mechanical ventilation (MV) requirement, hospital stay duration, and mortality rates. Results: Of the 604 screened, only 119 patients were included. The intervention group (63 patients) S/F ratio recovered versus the fall of the control group. Both groups had similar organ dysfunction and 28-day mortality. The intervention group had significantly (p < 0.001) fewer cases developing ARDS (9.5%) and MV (9.5%) than the control group (46.4% and 35.7%, respectively). Conclusions: The administration of inhaled budesonide and ipratropium bromide improved oxygenation, as assessed by the S/F ratio, and significantly reduced the rate of ARDS development and the requirement of MV versus the control group. Larger multi-center trials including diverse patient populations are needed to validate these results. Full article

Air filters are crucial components of building ventilation systems. Compared to conventional air filter media like glass fibers and melt-blown fibers, electrospinning membranes are more efficient for capturing various pollutants due to the smaller pores present on the structure. In this paper, activated carbon filters were prepared with eco-friendly polylactic acid (PLA) and microcrystalline cellulose (MCC) using electrospinning to obtain a high-quality factor (QF) fibrous mat for aerosol particle matter (PM) filtration and volatile organic compounds (VOCs) adsorption. Several configurations of the final membranes were investigated and tested for fiber morphology and air filtration performance. Filtering efficiency and adsorption properties were evaluated in a real-scale room by measuring the particle penetration of the newly synthesized and commercial filters against neutralized aerosol particles (3% NaCl aqueous solution) and VOCs (methyl ethyl ketone). The calculated depolluting efficiencies were up to 98% in terms of PM and 55% for VOCs abatement, respectively. Our results indicate that the proposed hybrid membranes represent promising materials for highly efficient and sustainable air filters for home application systems. Full article

Indoor air quality (IAQ) impacts human health, productivity, and well-being. As buildings become more energy-efficient and tightly sealed, the need for effective ventilation systems that maintain adequate IAQ grows. Energy Recovery Ventilators (ERVs) ensure adequate IAQ by bringing fresh outdoor air indoors while minimizing costly energy wastage. ERVs provide major economic, health, and well-being benefits and are a critical technology in the fight against climate change. However, little is known about the impact of ERV operation on the generation and fate of particulate and gaseous indoor air pollutants, including toxic, carcinogenic, allergenic, and infectious air pollutants. Specifically, the air pollutant crossover, aerosol deposition within ERVs, the chemical identity and composition of aerosols and volatile organic compounds emitted by ERVs themselves and by the accumulated pollutants within them, and the effects on bioaerosols must be investigated. To fill these research gaps, both field and laboratory-based experimental research that closely mimics real-life conditions within a controlled environment is needed to explore critical aspects of ERVs’ effects on indoor air pollution. Filling the research gaps identified herein is urgently needed to alert and inform the industry about how to optimize ERVs to help prevent air pollutant generation and recirculation from these systems and enhance their function of pollutant removal from residential and commercial buildings. Addressing these knowledge gaps related to ERV design and operation will enable evidence-based recommendations and generate valuable insights for engineers, policymakers, and heating, ventilation and air conditioning (HVAC) professionals to create healthier indoor environments. Full article

Houston, Texas, with its large-scale industrial activities, serves as a national hub for petrochemical processing and chemical feedstock production, making it a unique emission region for volatile organic compounds (VOCs) and production-related emissions. These emissions can be associated with industrial activities, including solvent usage and production to manufacture consumer products such as volatile chemical products. To support the Houston-based Dept. of Energy’s Atmospheric Measurement Radiation program-led Tracking Aerosol Convection ExpeRiment (TRACER) projects, VOCs were measured at the San Jacinto Battleground State Historic Site during September 2021 and 2022. The observed VOC mixing ratios reveal unique emission signatures for select VOCs, including benzene, toluene, acetone, and isoprene. Routine nighttime enhancements of these compounds exceeded the urban background, with mixing ratios increasing by up to 20 ppbv per hour and persisting for up to 6 h, suggesting that emissions from local industrial activities near the Houston Ship Channel (HSC) are impacting the site. For example, mixing ratios exceeding 15 ppbv for at least one VOC were observed on 58% of nights (n = 32 nights), with 19 nights (~35%) having two or more VOCs with mixing ratios above 15 ppbv. For select peak emission events, the NOAA dispersion model estimated plume transport across parts of the urban system, suggesting that VOCs from the HSC may impact local air quality. This study highlights the importance of VOC-related emissions from industrial production and supply chains in contributing to total VOC emissions in urban areas like Houston, Texas. Full article

Isoprene emissions can affect the oxidizing capacity of the atmosphere and are likely to increase with an increase in the world’s biomass. The emission of isoprene is strongest in tropical forested regions, suggesting a major portion of tropospheric chemistry occurs in the tropics. As well as deforestation and reforestation having a direct impact on the world’s climate through land cover, there is also an indirect environmental impact (e.g., global warming, air pollution) through the resulting change in isoprene emissions. Previously, incomplete understanding of isoprene oxidation chemistry caused a model-measurement breakdown for concentrations of HO_x radicals observed over certain low-NO_x regions, such as the pristine Amazon rainforest. Over the last decade, however, understanding of isoprene oxidation chemistry has been vastly improved. Numerous research studies have provided evidence for the involvement of 1,6-H and 1,5-H shift reactions in the isoprene oxidation mechanism, which increases the level of HO_x recycling that occurs. As well as helping to reduce the model-measurement breakdown observed, the updated isoprene oxidation mechanism affects the tropospheric burdens of other species, including carbon monoxide (CO), methane (CH₄), ozone (O₃), organic peroxides (ROOH), secondary organic aerosol (SOA), and organic nitrates (RONO₂). There are still gaps in the understanding of the impacts and oxidation chemistry of isoprene emissions, which this literature review identifies and discusses. In the future, there is still much scope for further research, including modeling future reforestation scenarios with isoprene emissions and their impacts on both global and regional scales. Full article

Background/Objectives: Chlamydia (C.) psittaci is an avian respiratory pathogen that regularly infects budgerigars (Melopsittacus undulatus) and is a known zoonosis. This study aimed to evaluate the efficacy of a nucleoside-modified mRNA vaccine formulated in lipid nanoparticles (LNPs), either with (mRNA Galsomes) or without (mRNA LNPs) the glycolipid antigen α-Galactosylceramide, in protecting budgerigars against C. psittaci genotype A infection. Methods: Three groups of eight budgerigars received two intramuscular vaccinations with PBS, mRNA LNPs or mRNA Galsomes, and were subsequently challenged via aerosol with the C. psittaci genotype A strain 90/1051. Vaccine efficacy was assessed over 14 days post challenge by monitoring clinical signs, macroscopic and microscopic lesions, pathogen excretion and chlamydial burden in organs. Antibody levels were evaluated at baseline, after vaccination and post challenge. Results: Both mRNA LNPs and mRNA Galsomes induced significant serum antibody responses post booster. Vaccination significantly reduced clinical signs, chlamydial burden in the lungs and macroscopic lesions in conjunctiva, conchae, lungs and thoracic airsacs, compared to controls. Additionally, mRNA Galsomes-treated birds showed a significantly reduced lung inflammation and fewer macroscopic lesions in abdominal airsacs and liver, compared to non-vaccinated animals. These animals also experienced a significantly lower chlamydial burden in the spleen, fewer clinical signs at day 11 and fewer fecal shedding at day 14 post challenge, compared to mRNA LNP-treated animals. Conclusions: This study demonstrated that mRNA vaccination confers partial protection against C. psittaci in budgerigars, with mRNA Galsomes appearing to provide enhanced efficacy. However, the absence of species-specific reagents for assessing cellular immunity in Psittaciformes limits a comprehensive understanding of vaccine-induced protection. The development of psittacine-specific T cell markers and cytokine assays is necessary to further elucidate immune mechanisms and optimize vaccine formulations. Full article

This study examines long-term trends in fine particulate matter (PM_2.5) composition and oxidative potential in Los Angeles based on data from the University of Southern California’s Particle Instrumentation Unit, with chemical composition retrieved from the EPA’s Air Quality System (AQS). While regulatory interventions have reduced PM_2.5 mass concentration and primary combustion-related components, our findings reveal a more complex toxicity pattern. From 2001 to 2008, the PM_2.5 oxidative potential, measured via the dithiothreitol (DTT) assay, declined from ~0.84 to ~0.16 nmol/min/m³ under stringent tailpipe controls. However, after this initial decline, PM_2.5 DTT stabilized and gradually increased from ~0.35 in 2012 to ~0.97 nmol/min/m³ by 2024, reflecting the growing influence of non-tailpipe emissions such as brake/tire wear. Metals, such as iron (Fe, ~150 ng/m³) and zinc (Zn, ~10 ng/m³), remained relatively stable as organic and elemental carbon (OC and EC) declined, resulting in non-tailpipe contributions dominating PM_2.5 toxicity. Although PM_2.5 mass concentrations were effectively reduced, the growing contribution of non-tailpipe emissions (e.g., brake/tire wear and secondary organic aerosols) underscores the limitations of mass-based standards and tailpipe-focused strategies. Our findings emphasize the need to broaden regulatory strategies, targeting emerging sources that shape PM_2.5 composition and toxicity and ensuring more improvements in public health outcomes. Full article

Black carbon (BC) aerosols emitted from biomass, fossil fuel, and waste combustion contribute to the radiation budget imbalance and are transported over extensive distances in the Earth’s atmosphere. These aerosols undergo physical and chemical modifications with co-existing aerosols (e.g., nitrate, sulfate, ammonium) through aging processes during long-range transport and are primarily removed from the troposphere by wet deposition. Using precipitation samples collected in North America between 26 October and 1 December 2020 by the National Atmospheric Deposition Program (NADP), we investigated the relationships between BC and both water-soluble ions and water-soluble organic carbon (WSOC) using Spearman’s rank coefficients. We then attempted to identify the sources of BC in the wet deposition using factor analysis (FA) and satellite data of fire smoke. BC showed a very strong correlation with nitrate (ρ = 0.83). Strong correlations were also found with WSOC, ammonium, calcium, and sulfate ions (ρ = 0.78, 0.74, 0.74, and 0.67, respectively). FA showed that BC was in the same factor as nitrate, ammonium, sulfate, and WSOC, indicating that BC could originate from secondary aerosol formation and biomass burning. Supported by satellite data of fire and smoke, BC and other correlated pollutants were believed to be associated with wildfire outbreaks in several states in the United States (US) during November 2020. Full article

Emissions from domestic coal burning are generally recognized as the cause of the lung cancer epidemic in Xuanwei City, Yunnan Province, China. To examine the physicochemical characteristics of airborne particles emitted from burning this locally sourced coal, PM_2.5 samples were collected from Hutou village which has high levels of lung cancer, and Xize village located approximately 30 km from Hutou without lung cancer cases. Transmission Electron Microscopy-Energy Dispersive X-ray (TEM-EDX) analysis was employed to study the physiochemical features and chemistry of individual particles. Sulfur and silica are the most abundant elements found in the airborne particles in both of the two villages. Fewer elements in aerosol particles were found in Xize village compared with Hutou village. Based on the morphologies and chemical compositions, the particles in Xuanwei can be classified into five types including composite particles (38.6%); organic, soot, tar balls, and biologicals (28.3%); sulfate (14.1%); fly ash (9.8%); and minerals (9.2%). The particles in Hutou village are abundant in the size range of 0.4–0.8 μm while that in Xize is 0.7–0.8 μm. Composite particles are the most common types in all the size ranges. The percentage of composite particles shows two peaks in the small size range (0.1–0.2 μm) and the large size ranges (2–2.3 μm) in Hutou village while that shows an even distribution in all size ranges in Xize village. Core-shell particles are typical types of composite particles, with the solid ‘core’ consisting of materials such as fly ash or mineral grains, and the shell or surface layer being an adhering soluble compound such as sulfates or organics. The heterogeneous reactions of particles with acidic liquid layers produce the core-shell structures. Typically, the equivalent diameter of the core-shell particles is in the range of 0.5–2.5 μm, averaging 1.6 μm, and the core-shell ratio is usually between 0.4 and 0.8, with an average of 0.6. Regardless of the sizes of the particles, the relatively high core-shell ratios imply a less aging state, which suggests that the core-shell particles were relatively recently formed. Once the coal-burning particles are inhaled into the human deep lung, they can cause damage to lung cells and harm to human health. Full article

This comprehensive review reports on concentrations, sources, emissions, and potential health effects from Semi-Volatile Organic Compounds (SVOCs) identified in the internal home environment in European residences. A total of 84 studies were identified, and concentrations were collated for inhalation exposure from dust, air and aerosol. A total of 298 individual SVOCs were identified and 67 compounds belonging to eight chemical classes: phthalates, flame retardants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), per- and polyfluorinated alkyl substances (PFAS), biocides, bisphenols and musks were prioritised. Phthalates are the most abundant SVOCs with DEHP being the most abundant in both the dust and aerosol phases (WAGMs 426.4 μg g⁻¹ and 52.2 ng m⁻³, respectively) followed by DBP for dust (WAGMs are 95.9 μg g⁻¹). In the air, the most abundant SVOCs are DiBP (284.1 ng m⁻³), DBP (179.5 ng m⁻³), DEHP (106.2 ng m⁻³) and DMP (27.79 ng m⁻³). Chemicals from all SVOC categories are emitted from building and construction materials, furnishings and consumer products, especially phthalates. Both legacy chemicals and their alternatives were detected. Complexities of reporting on SVOCs included differing sampling methodologies, multiple standards in their definition, lack of industry data, and toxicological data focused primarily on ingestion not inhalation exposures. Further research is recommended to develop the evidence base for potential health effects including via inhalation, reporting of emission rates and undertaking future monitoring studies. Full article

Water vapor is an active trace component in the troposphere and has a significant impact on meteorology and the atmospheric environment. In order to meet demands for high-precision water vapor and aerosol observations for numerical weather prediction (NWP), the China Meteorological Administration (CMA) deployed 49 Raman aerosol lidar systems and established the first Raman–Mie scattering lidar network in China (CARLNET) for routine measurements. In this paper, we focus on the water vapor measurement capabilities of the CARLNET. The uncertainty of the water vapor Raman channel calibration coefficient (Cw) is determined using an error propagation formula. The theoretical relationship between the uncertainty of the calibration coefficient and the water vapor mixing ratio (WVMR) is constructed based on least squares fitting. Based on the distribution of lidar in regions with different humidity conditions, the method of real-time calibration and quality control based on radiosonde data is established for the first time. Based on the uncertainty requirements of the World Meteorological Organization for water vapor in data assimilation, the calibration and quality control thresholds of the WVMR in regions with different humidity conditions are determined by fitting real-time lidar and radiosonde data. Lastly, based on the radiosonde results, the calibration algorithm established in this study is used to calibrate CARLNET data from October to December 2023. Compared with traditional calibration results, the results show that the stability and detection accuracy of the CARLNET significantly improved after calibration in regions with different humidity conditions. The deviation of the Cw decreased from 12.84~18.47% to 5.41~11.54%. The inversion error of the WVMR compared to radiosonde decreased from 1.05~0.46 g/kg to 0.82~0.34 g/kg. The reliability of the improved calibration algorithm and the CARLNET’s performance have been verified, enabling them to provide high-precision water vapor products for NWP. Full article

Diesel vehicles are recognized as significant mobile sources of particulate matter emissions. As a renewable and environmentally friendly alternative to conventional fossil diesel, biodiesel offers the benefit of reducing greenhouse gas emissions. However, existing research on biodiesel emissions primarily focuses on primary emissions, with a limited understanding of their impact on secondary organic aerosol (SOA) formation. In this study, a diesel engine test bench was employed under idle conditions using three commonly used biodiesel blends. Exhaust emissions were directly introduced into the HAP-SWFU chamber, a quartz glass smog chamber designed to characterize both primary emissions and SOA formation during the photochemical oxidation process. The black carbon and primary organic aerosol (POA) emission factors for the three biodiesel blends under idle conditions ranged from 0.31 to 0.58 g kg⁻¹ fuel and 0.99 to 1.06 g kg⁻¹ fuel, respectively. The particle size of exhaust particulates peaked between 20 and 30 nm, and nucleation-idle conditions were found to be the dominating mode. The SOA production factor was between 0.92 and 1.15 g kg⁻¹ fuel, and the SOA/POA ratio ranged from 1.35 to 2.37, with an average of 1.86. This study concludes that the POA emission factor for biodiesel under idle conditions is comparable to values reported in previous studies on pure diesel exhaust, with the maximum SOA production factor reduced by 38%. Full article