Search Results (270)

Sin Nombre virus (SNV) is the main causative agent of hantavirus cardiopulmonary syndrome (HCPS) in North America. SNV is transmitted via environmental biological aerosols (bioaerosols) produced by infected deer mice (Peromyscus maniculatus). It is similar to other viruses that have environmental transmission routes rather than a person-to-person transmission route, such as avian influenza (e.g., H5N1) and Lassa fever. Despite the lack of person-to-person transmission, these viruses cause a significant public health and economic burden. However, due to the lack of targeted pharmaceutical preventatives and therapeutics, the recommended approach to prevent SNV infections is to avoid locations that have a combination of low foot traffic, receive minimal natural sunlight, and where P. maniculatus may be found nesting. Consequently, gaining insight into the SNV bioaerosol decay profile is fundamental to the prevention of SNV infections. The Biological Aerosol Reaction Chamber (Bio-ARC) is a flow-through system designed to rapidly expose bioaerosols to environmental conditions (ozone, simulated solar radiation (SSR), humidity, and other gas phase species at stable temperatures) and determine the sensitivity of those particles to simulated ambient conditions. Using this system, we examined the bioaerosol stability of SNV. The virus was found to be susceptible to both simulated solar radiation and ozone under the tested conditions. Comparisons of decay between the virus aerosolized in residual media and in a mouse bedding matrix showed similar results. This study indicates that SNV aerosol particles are susceptible to inactivation by solar radiation and ozone, both of which could be implemented as effective control measures to prevent disease in locations where SNV is endemic. Full article

Ammonium nitrate (NH₄NO₃) is a major constituent of fine particulate matter (PM_2.5), playing a critical role in air quality and atmospheric chemistry. However, the dual regulatory role of ammonia (NH₃) in both the formation and volatilization of NH₄NO₃ under ambient atmospheric conditions remains inadequately understood. To address this gap, we conducted high-resolution field measurements at a clean tropical coastal site in China using an integrated system of Aerosol Ion Monitor-Ion Chromatography, a Scanning Mobility Particle Sizer, and online OC/EC analyzers. These observations were complemented by thermodynamic modeling (E-AIM) and source apportionment via a Positive Matrix Factorization (PMF) model. The E-AIM simulations revealed persistent thermodynamic disequilibrium, with particulate NO₃⁻ tending to volatilize even under NH_3gas-rich conditions during the northeast monsoon. This suggests that NH₄NO₃ in PM_2.5 forms rapidly within fresh combustion plumes and/or those modified by non-precipitation clouds and then undergoes substantial evaporation as it disperses through the atmosphere. Under the southeast monsoon conditions, reactions constrained by sea salt aerosols became dominant, promoting the formation of particulate NO₃⁻ while suppressing NH₄NO₃ formation despite ongoing plume influence. In scenarios of regional accumulation, elevated NH₃ concentrations suppressed NH₄NO₃ volatilization, thereby enhancing the stability of particulate NO₃⁻ in PM_2.5. PMF analysis identified five source factors, with NO₃⁻ in PM_2.5 primarily associated with emissions from local power plants and the large-scale regional background, showing marked seasonal variability. These findings highlight the complex and dynamic interplay between the formation and evaporation of NH₄NO₃ in NH_3gas-rich coastal atmospheres. Full article

Ambient fine particulate matter of size less than 2.5 μm in aerodynamic diameter (PM_2.5) is a key ambient air pollutant that has been linked to numerous adverse health outcomes. Reliable estimates of PM_2.5 are important for supporting epidemiological and health impact assessment studies. Precise measurements of PM_2.5 are available through networks of monitors; however, these are spatially sparse and temporally incomplete. Chemical transport model (CTM) simulations and satellite-retrieved aerosol optical depth (AOD) measurements are two data sources that have been used to develop prediction models for PM_2.5 at fine spatial resolutions with increased spatial coverage. As part of the Multi-Angle Imager for Aerosols (MAIA) project, a geostatistical regression model has been developed to bias-correct AOD, followed by Bayesian ensemble averaging to gap-fill missing AOD values with CTM simulations. Here, we present a suite of statistical software (available in the R package ensembleDownscaleR) to facilitate the adaptation of this modeling approach to other settings and air quality modeling applications. We describe the Bayesian ensemble averaging approach, model specifications, estimation methods, and evaluation via cross-validation that is implemented in the software. We also provide a case study of estimating PM_2.5 using 2018 data from the Los Angeles metropolitan area with an accompanying tutorial. All code is fully reproducible and available on GitHub, data are made on Zenodo, and the ensembleDownscaleR package is available for download on GitHub. Full article

A novel temporally resolved settle-plate air sampler was developed using 3D printing technology to improve upon traditional passive air sampling methods. Conventional settle plates provide cumulative measurements of particle or microbial loads over an entire sampling period, lacking the temporal resolution necessary to identify specific contamination events. The described device integrates a petri plate within a 3D-printed housing featuring a narrow slit that exposes only a small portion of the plate to incoming particles. A rotary mechanism, driven by a mechanical clock motor, rotates the petri plate over 12 h, allowing for time-segmented sampling. Validation experiments demonstrated the device’s ability to accurately encode the temporal history of particle deposition using both aerosolized dyes and viable microbial spores. The device effectively correlated bioaerosol deposition with ambient wind conditions during outdoor sampling. The system is inexpensive (under USD 10), requires no specialized skills to assemble, and is compatible with existing settle plate methodologies. This innovation enhances the ability to conduct air quality assessments in critical environments, enabling data-driven decisions to mitigate contamination risks. Full article

Accurate estimation of ambient PM_2.5 concentrations is crucial for assessing air quality and health risks, particularly in regions with limited ground-based monitoring. Satellite-retrieved data products, such as top-of-atmosphere reflectance (TOAR) and aerosol optical depth (AOD), are widely used for PM_2.5 estimation. However, complex atmospheric conditions cause retrieval gaps in TOAR and AOD products, limiting their reliability. This study introduced a spatiotemporal convolutional approach to fill sampling gaps in TOAR and AOD data from the Himawari-8 geostationary satellite over the Yangtze River Delta (YRD) in 2016. Four machine-learning models (random forest, extreme gradient boosting, gradient boosting, and support vector regression) were used to estimate hourly PM_2.5 concentrations by integrating gap-filled and original TOAR and AOD data with meteorological variables. The random forest model trained on gap-filled TOAR data yielded the highest predictive accuracy (R² = 0.75, RMSE = 18.30 μg m⁻³). Significant seasonal variations in PM_2.5 estimates were found, with TOAR-based models outperforming AOD-based models. Furthermore, we observed that a substantial portion of the YRD population in non-attainment areas is at risk of cardiovascular disease due to chronic PM_2.5 exposure. This study suggests that TOAR-based models offer more reliable PM_2.5 estimates, enhancing air-quality assessments and public health-risk evaluations. Full article

Eulerian observations of chemical species at fixed positions in a flow field are known to violate conservation laws, while observations tracking moving air parcels are practically unfeasible. Eulerian observations often cause positive correlations between the reactants and products in the atmosphere, which are frequently misinterpreted as evidence of the related chemical conversion. This dilemma has motivated innovative trials. The perturbation technique, widely used in mathematical and physical studies, offers a potential solution. Combining Eulerian observations with perturbation techniques may compensate for this weakness, making this approach particularly valuable for studying the gas–aerosol partitioning of semi-volatile particulate species in ambient air. As an example, we examined this combination through an adiabatic-expansion-induced perturbation study of the gas–aerosol partitioning of dimethylamine (DMA) and trimethylamine (TMA) in ambient air. Eulerian observations of chemical species in size-segregated atmospheric particles ranging from 10 μm to 0.056 μm, coupled with downstream adiabatic-expansion-induced perturbation observations, were performed in coastal and marine atmospheres using a commercial sampler (Nano-MOUDI-II, MSP, Shoreview, MN, USA), followed by an offline chemical analysis. The results revealed that particulate DMA generally tended to evaporate in ambient air during the observational periods, while enhanced adiabatic-expansion-induced perturbations occasionally led to the co-formation of DMAHNO₃ and NH₄NO₃. However, gaseous TMA apparently underwent gas–particle condensation to reach equilibrium in ambient air, with adiabatic-expansion-induced perturbation resulting in the formation of non-ionized TMA particulates. The thermodynamic analysis further supported that the observed particulate TMA was primarily determined by the equilibrium of gaseous TMA with non-ionized particulate TMA rather than ionic TMAH⁺. Full article

Recent observations have increasingly challenged the conventional understanding of atmospheric NH₃ and its potential sources in remote environments. Laboratory studies suggest that the microdroplet redox generation of NH₃ could offer an alternative explanation. However, key questions remain: (1) Can microdroplet redox generation of NH₃ occur in ambient air? (2) Is it restricted by the presence of specific catalysts? (3) What factors determine the efficiency of ambient NH₃ generation via microdroplet redox reactions? We investigate these questions based on adiabatic-expansion-induced perturbation observations performed in various atmospheres over the last decade. Our results indicate the adiabatic-expansion-induced generation of NH₃ + HNO₃ at ultrafast formation rates, with campaign-dependent stable stoichiometric ratios of HNO₃ to NH₃, as well as highly variable occurrence frequencies and efficiencies. These findings suggest that microdroplet redox reactions are more likely responsible for the generation of NH₃ + HNO₃ than conventional atmospheric NH₃ chemistry. Moreover, our analysis suggests that the line speed of microdroplets may be one of the key factors in determining the occurrence, stoichiometric ratio and efficiency of the redox reaction. Additionally, the presence of sea salt aerosols and low ambient temperature, rather than the specific catalysts, may significantly influence these processes. However, the current observational data do not allow us to derive a functional relationship between the redox reaction rate and these parameters, nor to fully detail the underlying chemistry. Comprehensive and controlled laboratory experiments, similar to our adiabatic-expansion-induced observations but utilizing state-of-the-art highly sensitive analyzers, would be necessary, though such experiments are beyond our current capabilities. Full article

In recent years, with the rapid socioeconomic development of Wuxi City, the frequent occurrence of severe air pollution events has attracted widespread attention from both the local government and the public. Based on the real-time monitoring data of criteria pollutants and GDAS (Global Data Assimilation System) reanalysis data, the spatiotemporal variation patterns, meteorological influences, and potential sources of major air pollutants in Wuxi across different seasons during 2019 (pre-COVID-19) and 2023 (post-COVID-19 restrictions) are investigated using the Pearson correlation coefficient, potential source contribution function (PSCF), and concentration-weighted trajectory (CWT) models. The results demonstrate that the annual mean PM_2.5 concentration in Wuxi decreased significantly from 39.6 μg/m³ in 2019 to 29.3 μg/m³ in 2023, whereas the annual mean 8h O₃ concentration remained persistently elevated, with comparable levels of 104.6 μg/m³ and 105.0 μg/m³ in 2019 and 2023, respectively. The O₃ and particulate matter (PM) remain the most prominent air pollutants in Wuxi’s ambient air quality. The hourly mass concentrations of criteria pollutants, except O₃, exhibited characteristic bimodal distributions, with peak concentrations occurring post-rush hour during morning and evening commute periods. In contrast, O₃ displayed a distinct unimodal diurnal pattern, peaking between 15:00 and 16:00 local time. The spatial distribution patterns revealed significantly elevated concentrations of all monitored species, excluding O₃, in the central urban zone, compared to the northern Taihu Lake region. The statistical analysis revealed significant correlations among PM concentrations and other air pollutants. Additionally, meteorological parameters exerted substantial influences on pollutant concentrations. The PSCF and CWT analyses revealed distinct seasonal variations in the potential source regions of atmospheric pollutants in Wuxi. In spring, the Suzhou–Wuxi–Changzhou metropolitan cluster and northern Zhejiang Province were identified as significant contributors to PM_2.5 and O₃ pollution in Wuxi. The potential source regions of O₃ are predominantly distributed across the Taihu Lake-rim cities during summer, while the eastern urban agglomeration adjacent to Wuxi serves as major potential source areas for O₃ in autumn. In winter, the prevailing northerly winds facilitate southward PM_2.5 transport from central-northern Jiangsu, characterized by high emissions (e.g., industrial activities), identifying this region as a key potential source contribution area for Wuxi’s aerosol pollution. The current air pollution status in Wuxi City underscores the imperative for implementing more stringent and efficacious intervention strategies to ameliorate air quality. Full article

Atmospheric intermediate volatile organic compounds (IVOCs) are important precursors of secondary organic aerosols (SOAs), and in-depth research on them is crucial for atmospheric pollution control. This review systematically synthesizes global advancements in understanding IVOC sources, emissions characterization, compositional characteristics, ambient concentrations, SOA contributions, and health risk assessments. IVOCs include long-chain alkanes (C₁₂~C₂₂), sesquiterpenes, polycyclic aromatic hydrocarbons, monocyclic aromatic hydrocarbons, phenolic compounds, ketones, esters, organic acids, and heterocyclic compounds, which originate from primary emissions and secondary formation. Primary emissions include direct emissions from anthropogenic and biogenic sources, while secondary formation mainly results from radical reactions or particulate surface reactions. Recently, the total IVOC emissions have decreased in some countries, while emissions from certain sources, such as volatile chemical products, have increased. Ambient IVOC concentrations are generally higher in urban rather than in rural areas, higher indoors than outdoors, and on land rather than over oceans. IVOCs primarily generate SOAs via oxidation reactions with hydroxyl radicals, nitrate radicals, the ozone, and chlorine atoms, which contribute more to SOAs than traditional VOCs, with higher SOA yields. SOA tracers for IVOC species like naphthalene and β-caryophyllene have been identified. Integrating IVOC emissions into regional air quality models could significantly improve SOA simulation accuracy. The carcinogenic risk posed by naphthalene should be prioritized, while benzo[a]pyrene requires a combined risk assessment and hierarchical management. Future research should focus on developing high-resolution online detection technologies for IVOCs, clarifying the multiphase reaction mechanisms involved and SOA tracers, and conducting comprehensive human health risk assessments. Full article

Primary Biological Aerosol Particles (PBAPs) range in size from a few nanometres to hundreds of micrometres and include particles such as pollen and fungal spores, which are significant due to their prevalence and potential to induce allergic reactions and other health-related issues. This study employs real-time fluorescence spectroscopy devices, the Wideband Integrated Bioaerosol Sensor (WIBS-NEO) and IBAC-2, to monitor PBAPs in the urban environment of Dublin, Ireland, during a six-week campaign in the summer of 2019. The WIBS-NEO demonstrated moderate correlations (R² = 0.5–0.7) in comparison with Hirst volumetric air sampler data for pollen and fungal spore concentrations following appropriate data filtering. In contrast, the IBAC-2 showed poor correlation with ambient fungal spore concentrations and lacked the necessary particle size ranges for reliable pollen measurement. Comparative analysis between WIBS-NEO and IBAC-2 revealed moderate correlation (R² ≈ 0.6) for small fluorescent particles (fluorescent particles between 0.7 and 1.5 μm optical diameter) but lower correlation for larger particles and specific bioaerosol types. The findings suggest that while the WIBS-NEO is effective for real-time bioaerosol monitoring, further refinement is needed for IBAC-2. This study underscores the potential of using advanced real-time monitoring tools in urban environments and highlights the need for continued development to address current limitations. Full article

A short comparison campaign took place at the Racibórz measurement site in May 2024 to assess the consistency of the Integrated Aerosol Monitoring Unit (IAMU), which houses three PM aerosol sensors (SPS30, OPC-N3, and OPS 3330) within a single enclosure. This assessment was supported by simultaneous measurements from two reference instruments (APS 3321 and SMP S3082), along with auxiliary observations from a ceilometer and meteorological station. To enhance particle transmission efficiency to the IAMU sensors, aerodynamic modeling of the inlet pipes was performed, accounting for particle density and diameter. The primary objective of this study was to evaluate the feasibility of using the IAMU, in conjunction with optimized inlet designs, for PM monitoring under varying ambient relative humidity and sensor temperature conditions. IAMU measurements have shown large absolute differences in PM values (exceeding one order of magnitude) with moderate (>0.54 for PM₁₀) to high (>0.82 for PM_2.5 and PM₁) temporal correlations. A calibration method was proposed, using reference instrument data and incorporating sensor temperature and air sample humidity information. The IAMU, combined with the developed calibration methodology, enabled the estimation of the aerosol growth factor, deliquescence point (RH ≈ 65%), and PM₁ hygroscopic parameter κ (0.27–0.56) for an industrial region in Poland. Full article

Numerous epidemiologic studies have used remote sensing to quantify the contribution of greenness, air pollution, and wildfire smoke to asthma and other respiration outcomes. This is the first review paper to evaluate the influence of remote sensing exposures on specific outcome severity and risk factors in different ecological settings. Literature searches utilizing PubMed and Google Scholar identified 61 unique studies published between 2009 and 2023, with 198 specific outcomes. Respiration-specific outcomes were lower in greenness and higher in air pollution and wildfire ecological settings. Aerosol optical depth (AOD)-PM_2.5 readings and specific outcomes were higher in economically developing than in economically developed countries. Prospective studies found prenatal and infant exposure to higher ambient AOD-PM_2.5 concentration level readings contributed to higher childhood asthma incidence. Lung function was higher in greenness and lower in the other two ecological settings. Age, environment, gender, other, and total risk factors showed significant differences between health outcomes and ecological settings. Published studies utilized physiologic mechanisms of immune, inflammation, and oxidative stress to describe obtained results. Individual and total physiologic mechanisms differed between ecological settings. Study results were used to develop a descriptive physiologic asthma model and propose updated population-based asthma intervention program guidelines. Full article

Building and finishing materials are among the main sources of indoor air pollution and can provide ideal substrates for microbial growth. Environmental factors can induce physico-chemical aging of these materials, altering their composition and increasing their vulnerability to microbial growth. To mitigate this risk, manufacturers are increasingly adding biocidal agents to these materials to prevent microbial contamination. The aim of this project was to study the sensitivity of two different acrylic paints to fungal growth, before and after an aging process, and to assess the impact of aging on the effectiveness of the biocides contained in these materials. To do this, two paints (antifungal and normal paint) were applied to a wall covering (polyester-cellulose) before being subjected to accelerated aging. The later process was based on the addition of detergent or water and exposing the material to a visible light spectrum, moderate temperature (38 ± 6 °C), and ambient relative humidity (25 ± 17%). Prior to 30 days of incubation, the aged and unaged (“native”) materials were inoculated with fungal spores using a dry aerosolization system. Fungi behavior was then evaluated by the culture method. The results showed that the native and water-aged normal acrylic paint supported fungal growth at 95 ± 5% relative humidity. However, the use of the cleaning product during the aging process provided additional resistance of the materials against fungal growth. On the other hand, the antifungal paint showed no visible growth due to its biocide content. The accelerated aging and incubation processes led to the depletion of the biocides and thus a decrease in their effectiveness against mold development. Full article

Bioaerosols, including airborne bacteria, are significant pollutants affecting both indoor and outdoor air quality, with implications for human health. Despite extensive research on indoor air quality, there is a notable lack of comprehensive data on ambient bacterial concentrations and their interactions with pollutants and meteorological factors. This review focuses on bacterial aerosols in the atmosphere, measured using the culture-based method, considered the “gold standard” for microorganism detection and identification. Studies reveal significant variability in bacterial concentrations across different environments and seasons, influenced by factors such as temperature, humidity, wind speed, solar radiation, and precipitation, underscoring the need for further research and monitoring to enhance health risk assessments and mitigation strategies. The presence of air pollutants such as particulate matter (PM) and ozone (O₃) further complicates these dynamics. The authors emphasize the need for more extensive research on outdoor bacterial aerosols and recommend that future studies prioritize detailed bioaerosol characterization to establish comprehensive exposure standards in ambient air, thereby improving public health protection and environmental management practices. Full article

In this study, online ambient volatile organic compounds (VOCs) were collected at an urban site of Zhengzhou in Central China during February 2018. The VOCs characteristics, source contributions and the Chinese New Year (CNY) effects have been investigated. During the sampling period, three haze periods have been identified, with the corresponding VOCs concentrations of (92 ± 45) ppbv, (62 ± 18) ppbv and (83 ± 34) ppbv; in contrast, the concentration during non-haze days was found to be (57 ± 27) ppbv. In addition, the festival effects of the CNY were investigated, and the concentration of particulate matter precursor decreased significantly. Meanwhile, firework-displaying events were identified, as the emission intensity had been greatly changed. Both potential source contribution function (PSCF) and the concentration weighted trajectory (CWT) models results indicated that short-distance transportation was the main influencing factor of the local VOCs pollution, especially by transport from the northeast. Source contribution results by the positive matrix factorization (PMF) model showed that vehicle exhaust (24%), liquid petroleum gas and natural gas (LPG/NG, 23%), coal combustion (21%), industrial processes (16%) and solvent usages (16%) were the major sources of ambient VOCs. Although industry and solvents have low contribution to the total VOCs, their secondary organic aerosol (SOA) contribution were found to be relatively high, especially in haze-1 and haze-3 periods. The haze-2 period had the lowest secondary organic aerosol potential (SOAp) during the sampling period; this is mainly caused by the reduction of industrial and solvent emissions due to CNY. Full article