Exhaled CO2 and aerosol dispersion on a cruise ship: Airflow and infection risk insights.

Abstract. A comprehensive study of aerosol exchange surface fluxes was conducted at a suburban site in Fairbanks (Alaska) during the Arctic winter as part of the ALPACA experiment. Aerosol fluxes were measured by an eddy covariance system on a snow-covered field located at the University of Alaska Fairbanks (UAF) Farm site from 26 January to 17 February 2022. Overall, the flux measurements indicate that the site acted mainly as an emission source for ultrafine particles, while the fluxes for larger particle sizes were substantially bidirectional. Median deposition velocities were 0.61, 0.04, and 8.73 mm s−1 for ultrafine (< 50 nm), accumulation (0.25–0.8 µm), and quasi-coarse (0.8–3 µm) particles, respectively. Anticyclonic synoptic meteorological conditions enhanced atmospheric stagnation and favoured pollutant accumulation near the surface, whereas cyclonic conditions increased aerosol dispersion, thus reducing deposition rates. Despite the frequent conditions of atmospheric stability and pronounced temperature inversions resulting from the strong surface radiative cooling, turbulence was generated mechanically by wind friction, leading to particle deposition. Our findings provide quantitative evidence that wintertime aerosol dry deposition in Arctic urban areas contributes significantly to pollutant accumulation in the snowpack, potentially enhancing contaminant remobilization during snowmelt. Finally, this study provides data for improving aerosol transport models and understanding pollutant-snow interactions in cold urban regions.

Abstract The spread of exhaled particles in a passenger aircraft cabin is an important parameter for evaluating infection risk modelling or the spread of other contaminants and odours. It is well known that the ventilation concept has a significant influence on this process and therefore also on the direct transmission of the contaminants. The present experimental study, conducted in the ground-based Do728 research aircraft cabin of the DLR, compares the aerosol spread under state-of-the-art mixing ventilation (MV) conditions with cabin displacement ventilation (CDV) and a combined CDV-MV ventilation (hybrid ventilation - HV). Various source positions in longitudinal direction and in the cross-section as well as different airflow distributions were investigated. Furthermore, the dynamic influence of people walking in the aisle was analyzed. This study shows that the spread of particles in a short-range aircraft is strongly affected by the installed ventilation system. Compared to the state-of-the-art MV, the mean concentration can be reduced by up to 80% under CDV conditions. Furthermore, the number of seats where certain thresholds are exceeded can be significantly reduced. By combining the systems to HV, the mean concentration can be reduced by 10% compared to MV. However, this results in a 130% increase in the maximum value. The spread of particles in case of MV and HV is strongly influenced by the source position, in both the longitudinal and in cross-sectional directions. Movement in the aisle has only a minor influence on the mean particle load and the number of seats above a certain threshold under MV conditions. However, the direction of spreading within the cabin is changed by the movement, decreasing the particle load in front and increasing it in the rear of the cabin. A considerably stronger effect was measured under CDV conditions, where the induced air flow by the manikin movement leads to increased particle concentrations in large area of the cabin. Here, the otherwise well-defined, upward-directed buoyancy driven flow which transports the exhaled particles directly to the exhaust, is now disturbed by the movement and thus more spreading of particles occurs in the breathing zone of the passengers.

The threat of chemical terrorism during an on-going russian invasion of Ukraine is among the most pressing concerns on the world war agenda. Modern armed conflicts demonstrate a qualitative shift in the nature of the chemical threat, manifested in the asymmetric and targeted use of chemical munitions with unmanned aerial vehicles (UAVs). This evolution poses significant challenges to traditional approaches to combined military training (in terms of Chemical, Biological, Radiological and Nuclear – CBRN – protection), which do not fully consider the specifics of such attacks. The purpose of the study is to develop scientifically substantiated recommendations for adapting the combined military training of the Defense Forces personnel to effectively counter the asymmetric use of chemical munitions via UAVs in the context of contemporary conflicts. The results of this research are based on a systematic and comparative analysis of current military doctrines, scientific publications, and experiences from modern armed conflicts (in particular, the full-scale invasion of Ukraine). Qualitative content analysis was applied to identify typical scenarios of chemical munitions use via UAVs, while an analytical review was implemented to assess current training protocols and existing technological solutions. Principles of the Delphi method were also applied to substantiate the personnel training needs in the context of asymmetric warfare. It was determined that asymmetric chemical attacks via UAVs are characterized by targeted container drops, aerosol dispersion, and the use of chemical explosives, resulting in localized impact zones and psychological pressure. The level of traditional training has been proven as insufficient due to emphasis on massed attacks, lack of exercises in rapid localized decontamination, and identification of small contamination foci. Additionally, the psychological impact of sudden UAV attacks necessitates enhanced attention to personnel resilience. The article justifies the need to integrate new modules into combined military training, encompassing expanded chemical protection training, operational decontamination, application of modern detection and counter-UAV measures, as well as strengthened psychological preparation for unanticipated threats. The proposed recommendations will contribute to enhancing the survivability and combat effectiveness of units in hybrid warfare conditions.

Predicting aerosol dispersion after confined explosions is critical for hazard mitigation. This study established a 1 m³ cubic explosion experimental system and a two-dimensional simulation model to quantify how pressure gradient, virtual mass, and thermophoretic forces drive particle transport. Results show pressure gradient force dominates near-field dispersion, increasing peak concentration by 23.2%. Virtual mass force causes 12% higher maximal errors than pressure gradient at 21.2 ms due to particle inertial effects. Thermophoresis reduces concentrations by 24.6% in near-field and 14.5% in far-field through thermal-gradient diffusion. These findings refine the two-phase flow model driven by explosions and support more reliable assessments of aerosol hazards in confined environments.

Numerical study on aerosol dispersion and infection risk controlling mechanism in an isolation ward with various ventilation strategies

Spray freeze-dried doxycycline nanoparticles for macrophage-targeted lung delivery.

The Permian-Triassic (P-Tr) transition (~252 Ma) witnessed Earth's most severe biocrisis, which has long been linked to Siberian Traps volcanism and associated environmental upheaval. Major perturbation of the global carbon (C) and sulfur (S) cycles is mainly inferred from marine δ13C and δ34S records, whereas few existing terrestrial records link δ34S fluctuations to widespread dispersal and fallout of volcanogenic sulfate aerosols. Mounting evidence, however, reveals that the collapse of P-Tr terrestrial ecosystems was diachronous, questioning a hypothesized globally synchronous common forcing. Here, we present records of pyritic multiple-S isotopes (δ34Spy and Δ33S) and bulk organic δ13C for a paleotropical peatland drill core (HK-1) from Southwest China. The δ34Spy variations define three distinct phases with a notable decline in δ34Spy across the P-Tr transition, suggesting substantially elevated terrestrial sulfate influx coincident with major carbon cycle perturbation. Notably, overall small positive Δ33S values (+0.01 to +0.12‰) rule out a dominant role for stratospheric sulfates. Collectively, the observed changes in δ13Corg, δ34Spy, and Δ33S support catastrophic collapse of the Cathaysian Flora leading to intensified weathering and sulfate release. This inferred event, slightly after the P-Tr marine extinction, postdates by several 100-ky terrestrial floral collapse and perturbation of the C-S cycles documented in the high-latitude Sydney Basin. Cross-latitudinal diachroneity of terrestrial ecosystem collapse and consequent C-S perturbation challenges the hypothesis of a single, global volcanic driver. Rather, regional deforestation and its cascading effects overprinted on the global perturbations of biogeochemical cycles emerge here as critical factors shaping Earth's largest recorded crisis.

Control of Viral Aerosol Dispersion During Simulated Dental Procedures

Polar ice cores preserve high-resolution archives of historical atmospheric transport, providing unique insights into long-term stratospheric processes. Here, we present the first subannual plutonium-239 (239Pu) deposition records from Greenland and Antarctic ice cores (1940 to 1980 CE). The limited or delayed fallout from Ivy Mike (1952 CE) compared to Operation Castle (1954 CE), despite their detonation in close proximity, exemplifies how stratospheric circulation and seasonal dynamics create periods of reduced transport to Antarctica. These records also reveal seasonal fallout patterns in Antarctica, with enhanced deposition during austral summers driven by stratosphere-troposphere exchange. Our findings refine current representations of global aerosol dispersion and provide additional constraints for modeling atmospheric processes, particularly those driven by volcanic eruptions and geoengineering interventions.

Introduction The accurate reconstruction and prediction of dust and polluted aerosol trajectories in educational environments are critical for assessing air quality and mitigating health risks. Traditional numerical models for aerosol transport rely on Eulerian or Lagrangian approaches, which often suffer from trade-offs between computational efficiency and physical accuracy. Eulerian models struggle with resolving small-scale turbulence, while Lagrangian tracking methods face challenges in capturing multiscale interactions effectively. Methods To address these limitations, we propose a deep learning-driven approach that integrates a hybrid Eulerian-Lagrangian computational model with machine learning-enhanced optimization. Our method employs a high-fidelity aerosol transport model incorporating stochastic corrections for sub-grid scale effects and adaptive meshing for efficient resolution of dynamic aerosol distributions. We introduce a data-driven optimization framework that leverages physics-informed neural networks to enhance predictive accuracy while reducing computational overhead. Results and Discussion Experimental validation demonstrates that our approach significantly outperforms conventional numerical methods in both accuracy and efficiency, making it highly suitable for real-time applications in educational environments. This study provides an innovative and scalable solution for understanding and mitigating aerosol dispersion in indoor spaces, contributing to improved air quality management and public health protection.

As urban areas grow, understanding the impact of built environments on aerosol distribution is crucial for accurate monitoring and forecasting of urban air quality and for the development of mitigation strategies. This study uses Large Eddy Simulation approach combined with Local Climate Zones (LCZ) classification to simulate the transport of Lagrangian aerosol particles in different urban configurations. The study simulates several urban configurations based on LCZ classification, specifically LCZ 4 (open high-rise), LCZ 5 (open mid-rise), and LCZ 6 (open low-rise), varying in building height and density. Both regular and randomized urban development configurations were examined to understand the impact of building geometry on particle dispersion. The study reveals that building orientation significantly influences particle distribution, with structures parallel to the wind adding horizontal dispersion and those perpendicular promoting vertical mixing. In randomized configurations, variations in particle concentrations highlight the role of architectural heterogeneity in turbulence development and aerosol dispersion. The findings suggest that aggregated block- or district-scale building geometry properties strongly influence aerosol transport. For randomized urban configurations, without idealized regular structures, the difference in the large-scale morphometric characteristics of specified LCZ types has a significantly greater impact on the particle dispersion process than the local geometric differences between configurations of the same LCZ type. Future research taking into account diverse meteorological conditions and more LCZ types is recommended to enhance the accuracy and applicability of this approach.

Enhanced aerosol dispersion of a sequential cough and social distancing implications.

Study on the air gap effect when closing toilet lid on droplet and pathogen escaping from flushing.

Aerosol dispersion dynamics and fallow time determination in a multi-chair dental office

Biomass burning in the Amazon region, especially during the dry season, generates aerosol dispersion events across the southern part of the continent, with impacts observable thousands of kilometers from the emission source. This study presents a long-range aerosol transport case from September 2024, in which smoke aerosols from forest fires in the central Amazon reached southeastern and southern Brazil, affecting the air quality in distant areas such as São Paulo and São Martinho. The event was simulated using the Weather Research and Forecasting model with Chemistry (WRF-Chem), configured with the MOZCART chemical mechanism, combined with MERRA-2 reanalysis data and by using the 3BEM biomass burning emission inventory. Satellite datasets from MODIS and MERRA-2 reanalysis were used to evaluate the model’s performance. The results indicate that the South American Low-Level Jet (SALLJ) played a key role in transporting carbonaceous aerosols over long distances. The model successfully captured the spatial and temporal evolution of the aerosol plume and its impacts, although it tended to underestimate aerosol optical depth (AOD) values compared with satellite observations. This study highlights the WRF-Chem’s capability to simulate extreme smoke transport events in South America and supports its potential application in forecasting and air quality assessments.

Characterization and mitigation of radioactive dust during graphite retrieval process of nuclear decommissioning.

The Qinghai-Tibet Plateau, known as the “third pole” of the Earth with an average elevation of approximately 4500 m, offers a unique natural laboratory for probing the dynamic behavior of the global electric circuit. In this study, we conduct a comprehensive analysis of near-surface vertical atmospheric electric field (AEF) measurements collected at the Gar Station (80.1° E, 32.5° N; 4259 m a.s.l.) on the western Tibetan Plateau, spanning the period from November 2021 to December 2024. Fair-weather conditions are imposed. The annual mean AEF at Gar is ∼0.331 kV/m, significantly higher than values observed at lowland and plain sites, indicating a pronounced enhancement in atmospheric electricity associated with high-altitude conditions. Moreover, the AEF exhibits marked seasonal variability, peaking in December (∼0.411–0.559 kV/m) and valleying around July–August (∼0.150–0.242 kV/m), yielding an overall amplitude of approximately 0.3 kV/m. We speculate that this seasonal pattern is primarily driven by variations in aerosol concentration. During winter, increased aerosol loading from residential heating and vehicle emissions due to incomplete combustion reduces atmospheric conductivity by depleting free ions and decreasing ion mobility, thereby enhancing the near-surface AEF. In contrast, lower aerosol concentrations in summer lead to weaker AEF. This seasonal decline in aerosol levels is likely facilitated by stronger winds and more frequent rainfall in summer, which enhance aerosol dispersion and wet scavenging, whereas weaker winds and limited precipitation in winter favor near-surface aerosol accumulation. On diurnal timescales, the Gar AEF curve deviates significantly from the classical Carnegie curve, showing a distinct double-peak and double-trough structure, with maxima at ∼03:00 and 14:00 UT and minima near 00:00 and 10:00 UT. This deviation may partly reflect local influences related to sunrise and sunset. This study presents the longest ground-based AEF observations over the Qinghai–Tibet Plateau, providing a unique reference for future studies on altitude-dependent AEF variations and their coupling with space weather and climate processes.

The oil and gas industry is characterized by the presence and operation of various high-risk facilities, which contribute to occupational injuries and diseases, as well as environmental pollution. Among these, pipeline systems – particularly main gas pipelines – are prominent. The purpose of this research is to study the processes involved in the manual arc welding of main gas pipelines during construction and repair, which adversely affect human health and the environment. Gas pipeline welding during construction and repair is performed both in semi-enclosed spaces and in the open air. In both cases, manual arc welding is predominantly used due to its mobility and ease of implementation. The equipment required for arc welding is much cheaper and simpler than that used for laser, electron beam, or hybrid welding. These advantages have led to the widespread use of arc welding across various industries. However, manual arc welding has a considerable negative impact on human health and the environment due to the emissions of toxic substances in the form of welding aerosols. The regularities of aerosol formation during arc welding and the mechanisms of their distribution in the environment are examined, enabling the planning of welding operations in a way that reduces the risk of occupational diseases. Empirical correlations were obtained to determine the concentrations of harmful substances. It was shown that an aerosol cloud, dispersed by wind, spreads with particles diffusing in all directions, leading to a rapid decrease in concentration. It was found that during the welding of pipes under moderate wind conditions, aerosol smoke from a point source spreads in the air in a conical torch shape, expanding both vertically and horizontally. It is substantiated that the main physical process involved is diffusion combined with heat transfer due to convective airflows. Based on Sutton’s modified mathematical model, it was established that during the welding of above-ground pipelines under laminar wind conditions, aerosol smoke mixes with air solely through molecular diffusion, whereas during underground welding, aerosol dispersion is caused by the physical processes associated with the formation of a welding torch.

Modeling indoor contaminant dispersion is crucial for exposure analysis in fields like occupant safety and infection prevention. Accurate predictions necessitate appropriate computational approaches because numerical solutions to turbulent indoor flow conditions are vulnerable to modeling errors. Large-eddy simulation (LES) is a turbulence-resolving approach with the potential to describe the relevant flow physics governing indoor contaminant dispersion. This work documents a quantitative validation study of the PALM LES model against experimental indoor dispersion measurements. The experiments were conducted in a controlled chamber with a mechanical ventilation system operated at two different ventilation flow rates (2 and 5 air changes per hour). The LES results were obtained using three different resolutions (1, 1.5, and 2 cm), labeled Fine, Medium, and Coarse. The evolution of particle concentration was monitored identically in the chamber and the LES model using a multipoint measurement network. The validation analysis assessed the performance of the PALM LES model in predicting aerosol dispersion using four validation metrics. The results indicated strong performance for the fine model under both ventilation rates. Validation performance declined with reduced resolution, and the coarse model demonstrated evidently lower accuracy due to deficiencies in capturing thermal stratification effects. Sensitivity analysis revealed that the validation results were largely unaffected by changes in thermal boundary conditions. This study highlights the importance of model resolution in predicting indoor contaminant dispersion and cautions against assuming predictive capacity in thermal modeling based on dispersion modeling results.