Aerosol Filtration Research Articles

Plutonium isotopes in the ground air layer in southern Poland (2010–2016): Source terms, seasonal variability and correlations with meteorological conditions

In this study, the results of the analysis of Pu-238 and Pu-239 + 240 activity concentrations on aerosol filters collected from 2010 to 2016 in Krakow (Southern Poland) are presented and discussed. For the first time, the temporal variation of Pu-239 + 240 activity concentration in surface air in Poland was studied using Fourier analysis. The analysis clearly showed that the Pu-239 + 240 content in the near-ground air layer is subject to seasonal variations and demonstrates annual periodicity. Pu analyses were performed using alpha spectrometry. The measured values ranged from 1.93∙10−10 Bq/m3 to 1.31∙10−8 Bq/m3 with an average of 2.07∙10−9 Bq/m3 for Pu-239 + 240 and from 9.07∙10−11 Bq/m3 to 1.27∙10−9 Bq/m3 with the average 1.52∙10−10 Bq/m3 for Pu-238. The analysis of the potential sources of plutonium isotopes in the air aerosols samples indicated that only two samples are uniquely characterized by the ratio corresponding to spent nuclear fuel: February 2012 (0.59 ± 0.18) and February 2015 (0.68 ± 0.19). The remaining samples showed mixed origins, with global radioactive fallout appearing to contribute more than spent nuclear fuel. To study the relationship between Pu-239 + 240 and meteorological conditions, Pearson's correlation and circulation pattern analyses were performed. The analyses showed that the Pu-239 + 240 activity concentration depends on air temperature (R = 0.51), the sum of ice and snowfall (R = −0.45), relative humidity (R = −0.54) and mean total cloud cover (R = −0.56). High concentrations of Pu-239 + 240 were positively correlated with air advection from the southern and eastern sectors, whereas low concentrations were observed during dynamic weather conditions with intense circulation from the western sector. In case of Pu-238 no significant correlation was observed.

Pressure Drop Dynamics during Filtration of Mixture Aerosol Containing Water, Oil, and Soot Particles on Nonwoven Filters.

The pressure drop dynamics during the filtration of three-component mixture aerosols are investigated and compared with two and single-component aerosols. The main area of interest is the effect of the addition of a small quantity of liquid (oil) and solid (soot) particles during the filtration of aerosol containing water mist. In addition, calculations of the change in filter mass during oil aerosol filtration have been carried out and compared with the experimental results. The new, improved filtration efficiency model takes into account a better coefficient fitting in the filtration mechanism equations. The limitations in the change in fibre diameter and packing density resulting from the filter loading have been implemented in the model. Additionally, the calculation model employs the fibre size distribution representation via multiple average fibre diameters. The changes in fibre diameter are dependent on each fibre's calculated filtration efficiency. The improved filtration model has been utilised to predict the mass change of the filters during the filtration of pure and mixture aerosols. The pressure drop calculation model based on changes in filter mass has been formulated. The model is then utilised to calculate pressure drop changes resulting from the filtration of the oil aerosol and water and oil mixture aerosol.

A dual-geometry pore-size-resolved model to predict deep-bed loading in a wall-flow filter

A gasoline particulate filter (GPF) is an effective wall-flow technology for gasoline engine particulate matter (PM) emission control via deep-bed filtration through porous ceramic walls within a honeycomb channel structure. An analytical filter model is desired to understand its efficiency and pressure drop under engine operating conditions and, thereby, reduce the development costs for meeting emission regulations and engine performance targets. Most existing models either oversimplify the filter geometry or do not offer good predictions in the soot loading regime. The present work treats the deep bed regime as two co-existing filters with different geometries based on their natural morphologies, one that describes the porous wall and the other for the fiber structure created by soot deposition. Both models are dynamic to account for changes in pore size distribution and soot dendrite growth during loading. Model validation by 12 sets of experimental filter loading data shows that it provides reasonable predictions of both filter efficiency and pressure drop during deep-bed loading for different GPF wall-flow filters under various operating conditions. Scanning electron microscopy (SEM) confirms model predictions for the unit collector size of the dendritic filter formed by soot deposition. Numerical simulation using GeoDict was also carried out to validate the model predictions on particle deposition location. The model is used to investigate the evolution of pore-size-resolved aerosol flow, filtration efficiency, mass loading, and particle packing density during loading. The impact of porosity, mean pore size, and pore size distribution on filter loading performance is studied. The results suggest that increasing porosity, narrowing pore size distribution, and increasing mean pore size can improve filter performance, offering pathways for future filter optimization.

Influence of Oil Content on Particle Loading Characteristics of a Two-Stage Filtration System

Filter media may encounter aerosols mixed with solid and oil ingredients from various sources, such as industries, transportation, and households, in the air purification process, while the influence such oil content has on the loading performance of single-stage and two-stage filtration systems is under-reported. Thus, this study aims to evaluate oil fraction effects on the loading performance of single-stage and two-stage filtration systems. First, to reveal the oil–solid mixed particle deposition mechanisms, the filter media parameters, i.e., specific cake resistance ε and cake porosity K2, were tested, indicating that a slight amount of oil can increase the dust holding capacity (DHC) of filters by forming a more porous cake, while an excess of oil results in reduced DHC by forming impermeable liquid films on the solid skeleton. Further two-stage experimental results indicate that the effectiveness of a pre-stage filter can be significantly affected by the properties of incoming aerosol and main-stage filters. The utilization of a pre-stage filter unintentionally deteriorated the service lifetime of the main-stage filter when challenged with contaminants with certain oil particles. This counter-intuitive negative phenomenon is due to the special loading behaviors of oil–solid mixed particles. The existing pre-stage filters allow a higher fine oil particle fraction to reach the main-stage downstream, while the induced cake filtration scenario leading to a film clogging scenario adversely reduced the lifetime of the main-stage filter. The findings suggest that the feasibility of a pre-stage in the filtration system requires compressive evaluations according to the specific oil-coated contaminants.

Quantitative Assessment of Airborne Transmission of Human and Animal Influenza Viruses in the Ferret Model

The WHO has developed a tool to assess the risk of newly emerging influenza viruses with pandemic potential (TIPRA). According to TIPRA, the main parameters for assessing the risk of human-to-human transmission of a novel influenza virus are its ability to bind to human cell receptors of the upper respiratory tract (URT) and transmit in model animals. The aim of this study was to quantify airborne transmission of human and animal influenza viruses in the ferret model. The transmission of influenza viruses was studied in the ferret model in an aerobiology chamber. Airborne particles concentration and fractional composition in the aerobiology chamber were measured using an aerosol particle counter and analytical aerosol filters. Viral load in ferret nasal washings and aerosol filters was determined by titration in MDCK cells and quantitative RT-PCR. Genetic analysis of influenza viruses was performed using virus genome sequences obtained by NGS. After intranasal infection, human and animal influenza viruses replicated in the cells of nasal mucosa in ferrets. The level of virus airborne particles contamination provided by infected animals depends on the infectious dose and differs significantly between influenza virus strains. The studied avian influenza viruses show insufficient transmission in the ferret model, while human and swine influenza viruses are highly transmitted in ferrets. We propose a quantitative model of airborne transmission of influenza virus from donor to recipient ferrets. Level of influenza virus transmission in the ferret model correlates with genetic markers of virus receptor specificity and the level of virus airborne particle contamination induced by donor ferrets.

Characteristics and Oxidative Potential of Ambient PM2.5 in the Yangtze River Delta Region: Pollution Level and Source Apportionment

Fine particulate matter (PM2.5) is a major contributor to the degree of air pollution, and it is associated with a range of adverse health impacts. Moreover, the oxidative potential (OP, as a tracer of oxidative stress) of PM2.5 has been thought to be a possible determinant of its health impact. In this study, the OP of 136 fine aerosol filter samples collected in Changzhou in two seasons (spring and summer) were determined using a dithiothreitol (DTT) assay. Source apportionments of the PM2.5 and DTT activity were further performed. Our results showed that the daily average ± standard deviation of the DTTv (volume-normalized DTT activity) in the PM2.5 was 1.16 ± 0.58 nmol/min/m3 and 0.85 ± 0.16 nmol/min/m3 in the spring and summer, respectively, and the DTTm (mass-normalized DTT activity) was 13.56 ± 5.45 pmol/min/μg and 19.97 ± 6.54 pmol/min/μg in the spring and summer, respectively. The DTTv was higher in the spring compared to the summer while the opposite was true for the DTTm. Most of the detected components (including the organic component, element component, NH4+, Mn, Cu, Zn, etc.) exhibited a moderately positive correlation with the DTTv, but the opposite was found with the DTTm. An aerodyne high-resolution aerosol mass spectrometer (HP-AMS) was deployed to probe the chemical properties of the water-soluble organic matter (WSOA). Positive matrix factorization (PMF) coupled with multiple linear regression was used to obtain the relative source contributions to the DTT activity for the WSOA in the PM2.5. The results showed that the sensitivity sequences of the DTTv to the WSOA sources were oxygenated organic aerosol (OOA) > biomass burning OA (BBOA) > hydrocarbon-like OA (HOA) in the spring and HOA > nitrogen-enriched OA (NOA) > OOA in the summer. The PMF suggested the highest contribution from traffic emissions to the DTTv of the PM2.5 in both seasons. Our findings point to the importance of both organic components from secondary formation and transition metals to adverse health effects in this region. This study can provide an important reference for adopting appropriate public health policies regarding the detrimental outcomes of exposure to PM2.5.

Trapping virus-loaded aerosols using granular material composed of protein nanofibrils and iron oxyhydroxides nanoparticles

The ongoing COVID-19 pandemic has revealed that developing effective therapeutics against viruses might be outpaced by emerging variants, waning immunity, vaccine skepticism/hesitancy, lack of resources, and the time needed to develop virus-specific therapeutics, emphasizing the importance of non-pharmaceutical interventions as the first line of defense against virus outbreaks and pandemics. However, fighting the spread of airborne viruses has proven extremely challenging, much more if this needs to be achieved on a global scale and in an environmentally-friendly manner. Here, we introduce an aerosol filter media made of granular material based on whey protein nanofibrils and iron oxyhydroxides nanoparticles. The material is environmentally-friendly, biodegradable, and composed mainly of a dairy industry byproduct. It features filtration efficiencies between 95.91% and 99.99% for both enveloped and non-enveloped viruses, including SARS-CoV-2, the influenza A virus strain H1N1, enterovirus 71, bacteriophage Φ6, and bacteriophage MS2. While the filtration efficiencies were relatively high, they came at the cost of high pressure drop (≈0.03 bar). We believe that the methods and results presented here will contribute to advancing our understanding of granular-based aerosol filters, hopefully helping the design of highly-efficient granular media with low-pressure drops.

An optimised organic carbon ∕ elemental carbon (OC ∕ EC) fraction separation method for radiocarbon source apportionment applied to low-loaded Arctic aerosol filters

Abstract. Radiocarbon (14C) analysis of carbonaceous aerosols is used for source apportionment, separating the carbon content into fossil vs. non-fossil origin, and is particularly useful when applied to subfractions of total carbon (TC), i.e. elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC), and water-insoluble OC (WINSOC). However, this requires an unbiased physical separation of these fractions, which is difficult to achieve. Separation of EC from OC using thermal–optical analysis (TOA) can cause EC loss during the OC removal step and form artificial EC from pyrolysis of OC (i.e. so-called charring), both distorting the 14C analysis of EC. Previous work has shown that water extraction reduces charring. Here, we apply a new combination of a WSOC extraction and 14C analysis method with an optimised OC/EC separation that is coupled with a novel approach of thermal-desorption modelling for compensation of EC losses. As water-soluble components promote the formation of pyrolytic carbon, water extraction was used to minimise the charring artefact of EC and the eluate subjected to chemical wet oxidation to CO2 before direct 14C analysis in a gas-accepting accelerator mass spectrometer (AMS). This approach was applied to 13 aerosol filter samples collected at the Arctic Zeppelin Observatory (Svalbard) in 2017 and 2018, covering all seasons, which bear challenges for a simplified 14C source apportionment due to their low loading and the large portion of pyrolysable species. Our approach provided a mean EC yield of 0.87±0.07 and reduced the charring to 6.5 % of the recovered EC amounts. The mean fraction modern (F14C) over all seasons was 0.85±0.17 for TC; 0.61±0.17 and 0.66±0.16 for EC before and after correction with the thermal-desorption model, respectively; and 0.81±0.20 for WSOC.

Изучение эффективности и прозрачности огнетушащих аэрозолей

Fire-extinguishing aerosol particles efficiently suppress the flame combustion but worsen evacuation conditions due to a decrease in the atmospheric transparency. After deposition, the particles create a corrosive environment. In addition, solid particles negatively affect the operation of devices moving parts and mechanisms. Removal of aerosol particles from the object is significantly difficult, especially from the closed cavities of devices, computers, etc. Known studies contain sufficiently detailed information about the fire-extinguishing ability of various formulations of an aerosol-forming composition considering the conditions for their use. Less attention is paid to the transparency study of gas media with micron-sized particles both in our country and abroad. At the same time, the study of fire extinguishing ability in relation to the transparency of the aerosol is extremely rare. Therefore, a study aimed at finding the mutual dependence of the aerosol-forming composition on the aerosol transparency is an urgent task. The article proposes a calculated dependence for calculating the transparency index of a medium with an aerosol on the concentration and average diameter of the particles, while noting the convergence of the results of calculation and experiment. All the experimental data on the transparency of fire-extinguishing aerosol correlate with the known data on the dispersion of aerosol particles, which were obtained by the laser diffraction method. In this case, the dispersion assessment was carried out in a fairly simple way without use of the sophisticated equipment. The medium transparency index and the fire-extinguishing ability of the aerosol are considered in interrelation. A series of experimental data was processed for the number of compounds of the aerosol-forming composition. As a result of data generalization, the dependence of the aerosol-forming compounds minimum extinguishing ability on the aerosol transparency in the range from zero to 100 % was obtained. It is shown that the use of aerosol filtration allows to increase the medium transparency to 50 % or more due to reducing the concentration of particles and increasing their size. For all the compounds, the mass of the aerosol-forming composition increases, the combustion of which leads to an efficient fire extinguishing and more transparent aerosol. The application of the obtained results allows to reduce the volume of fire experiments in the development of new efficient and safe aerosol-forming compositions for fire extinguishing, as well as in the study of the transparency of media with aerosol.

Advanced simulation techniques for the transport of routine atmospheric discharges using the JRODOS system

This work is dedicated to a study of routine atmospheric discharges from the Dukovany Nuclear Power Plant (NPP), Czechia. Radionuclide discharges and their transport in the environment were simulated using the JRODOS system. JRODOS was originally designed to forecast the atmospheric transport of radionuclide releases. However, the potential of JRODOS can be widened with the use of external scripts. Routine discharges can be simulated as 1-h immediately following discharges when they are summed and rescaled in accordance with the actual discharged activities. For calculations of routine discharges, we selected artificial radionuclides measured in the spectra of aerosol filters originating from the vicinity of the Czech NPPs. According to the simulated map of volumetric activities integrated over a longer period, new aerosol sampling sites can be proposed in the surroundings of the NPP of interest. The simulations have also been compared with the detection levels of selected radionuclides detected on aerosol filters.

Smart Face Masks for COVID-19 Pandemic Management: A Concise Review of Emerging Architectures, Challenges and Future Research Directions

Smart sensing technology has been playing tremendous roles in digital healthcare management over time with great impacts. Lately, smart sensing has awoken the world by the advent of smart face masks (SFMs) in the global fight against the deadly Coronavirus (Covid-19) pandemic. In turn, a number of research studies on innovative SFM architectures and designs are emerging. However, there is currently no study that has systematically been conducted to identify and comparatively analyze the emerging architectures and designs of SFMs, their contributions, socio-technological implications, and current challenges. In this article, we investigate the emerging SFMs in response to Covid-19 pandemic and provide a concise review of their key features and characteristics, design, smart technologies, and architectures. We also highlight and discuss the socio-technological opportunities posed by the use of SFMs and finally present directions for future research. Our findings reveal four key features that can be used to evaluate SFMs to include reusability, self-power generation ability, energy awareness and aerosol filtration efficiency. We discover that SFM has potential for effective use in human tracking, contact tracing, disease detection and diagnosis or in monitoring asymptotic populations in future pandemics. Some SFMs have also been carefully designed to provide comfort and safety when used by patients with other respiratory diseases or comorbidities. However, some identified challenges include standards and quality control, ethical, security and privacy concerns.

Effects of E-Cigarette Liquid Ratios on the Gravimetric Filter Correction Factors and Real-Time Measurements.

Electronic cigarettes (ECIGs) generate high concentrations of particulate matter (PM), impacting the air quality inhaled by humans through secondhand exposure. ECIG liquids are available commercially and some users create their own "do-it-yourself" liquids, and these liquids often vary in the amounts of their chemical ingredients, including propylene glycol (PG) and vegetable glycerin (VG). Previous studies have quantified PM concentrations in ECIG aerosol generated from liquids containing different PG/VG ratios. However, the effects of these ratios on aerosol instrument filter correction factors needed to measure PM concentrations accurately have not been assessed. Thus, ECIG aerosol filter correction factors for multiple aerosol instruments (SMPS + APS, MiniWRAS, pDR, and SidePak) were determined for five different PG/VG ratios 1) 0PG/100VG, 2) 15PG/85VG, 3) 50PG/50VG, 4) 72PG/28VG, and 5) 90PG/10VG and two different PM sizes, PM1 (1 μm and smaller) and PM2.5 (2.5 μm and smaller). ECIG aerosols were generated inside a controlled exposure chamber using a diaphragm pump and a refillable ECIG device for all the ratios. In addition, the aerosol size distribution and mass median diameter were measured for all five ECIG ratios. PM2.5 correction factors (5-7.6) for ratios 1, 2, 3, and 4 were similar for the SMPS + APS combined data, and ratios 1, 2, 3 were similar for the MiniWRAS (~2), pDR (~0.5), and SidePak (~0.24). These data suggest different correction factors may need to be developed for aerosol generated from ECIGs with high PG content. The higher correction factor values for the 90PG/10VG ratio may have resulted from greater PG volatility relative to VG and sensor losses. The correction factors (ratios 1-4) for PM2.5 were SMPS + APS data (4.96-7.62), MiniWRAS (2.02-3.64), pDR (0.50-1.07), and SidePak (0.22-0.40). These data can help improve ECIG aerosol measurement accuracy for different ECIG mixture ratios.

Біріккен Ұлттар Ұйымының бағдарламасы туралы «Еуропадағы ауыр металдардың атмосфералық шөгінділері - биомонитор мүктерін талдауға негізделген бағалаулар»

Одним из важнейших аспектов в решении задач охраны окружающей среды и здоровья человека является контроль качества атмосферного воздуха. К наиболее опасным загрязнителям окружающей среды относятся тяжелые металлы (ТМ). В большинстве европейских стран потребность в изучении последствий их воздействия на окружающую среду и здоровье человека привела к созданию национальных и международных программ по биомониторингу атмосферных выпадений тяжелых металлов. Данные об атмосферных выпадениях ТМ и других токсичных элементов собираются на основе анализа мхов-биомониторов, служащих аналогом аэрозольных фильтров. Под эгидой Комиссии ООН по трансграничному переносу атмосферных выпадений в Европе (UNECE ICP Vegetation) каждые 5 лет издается Атлас атмосферных выпадений тяжелых металлов. В статье сообщается об вкладе интернационального коллектива сектора нейтронного активационного анализа и прикладных исследований ЛНФ ОИЯИ в эти Атласы, начиная с 1995 года. Изучение атмосферных выпадений тяжелых металлов и других токсичных элементов в ряде стран-участниц и неучастниц ОИЯИ (Азербайджан, Албания, Армения, Беларусь, Болгария, Греция, Грузия, Казахстан, Молдова, Польша, Румыния, Словакия, Западная Украина, Северная Македония, Сербия и Хорватия), включая некоторые территории Центральной России (Московская, Тульская, Тверская, Ивановская, Ярославская, Владимирская, Самарская, Рязанская области), а также Южный Урал и Северный Кавказ (Республика Ичкерия, Северная Осетия) позволило выявить и оценить ареалы этих загрязнений на исследованных территориях и провести сравнение с уровнями аналогичных загрязнений в странах Западной Европы. В настоящее время обсуждается возможность расширения этой программы на страны Азии и Тихоокеанского побережья.

Modeling oil–mist filtration through coalescence filter media in the presence of gravity-induced flows

This paper jointly addresses numerical and physical challenges related to the modeling of coalescence filtration through vertical filter cartridges, put forth in the following papers by Starnoni, M. and C. Manes:• Starnoni, M., & Manes, C. (2021). A multiphase multicomponent flow and transport model for liquid aerosol filtration in coalescence fibrous filters. Separation and Purification Technology, 266, 118574.• Starnoni, M., & Manes, C. (2022). On the interplay between pressure and gravitational forces in coalescence filters. Journal of Aerosol Science, 105953.In particular, it provides the multidimensional extension of the one-dimensional model presented in Starnoni and Manes (2021) to the general case where internal gravity-induced flows play an effective role. Key to the implementation is the decomposition of the moving oil volumes along the different directions proportionally to the dimensionless number SM, a new quantity introduced in Starnoni and Manes (2022) describing the interplay between the forces dictating the oil dynamics. To validate the implementation, an experimental setup available in the literature is replicated, showing very good agreement in terms of all relevant quantities, namely saturation, pressure drop and drainage volumes. A generalized ‘Network, Channel and Film’ model is also formulated, which extends the scope of application of the original Jump and Channel model by Kampa et al. (2014) to filters with coarser fibrous microstructure. In particular, the existence of an additional flow mechanism termed ‘network’ is postulated, which is characterized by a complex multidimensional oil patterns configuration spanning the entire filter’s height and evolving, in a macroscopic sense, along the direction identified by SM.

Numerical Simulation of a CAM-Measured Spectra Influenced by Coarse Aerosol

In nuclear facilities, the mandatory atmosphere surveillance is operated by Continuous Air Monitors. This standalone instrument is designed to measure the airborne aerosol activity concentration and to trig an alarm signal when a predetermined activity concentration is exceeded. However, a rapid resuspension event of coarse aerosol leads to a measurement error: the airborne aerosol activity concentration is over-evaluated. Prior results have shown that the coarse aerosol deposit disturbs the background evaluation for the radioactivity measurement. The interactions between radioactive aerosols (with radon daughters) and coarse non-radioactive aerosols have to be investigated by running together aerosol models and nuclear simulations. Therefore, this paper investigates different ways to represent an aerosol deposit in numerical simulations. We developed two numerical aerosol deposit models that we integrated into Geant4, a tool for the simulation of the passage of radiations through matter, and then compared these to experimental results. The simplest model was discarded, and by using the second model, we managed to correctly frame our simulation results as an experimental measurement: an aerosol has been correctly considered in a nuclear simulation. By combining theory, simulations, and experimentations on both aerosol science and nuclear physics, this research will be able to improve the comprehension of monitors’ behaviour in delicate situations and, more broadly, the filtration of aerosols using radioactivity.

Prototype N95 Sterilizer: An Alternative Solution during Personal Protective Equipment Crisis

The high demand for N95 masks, especially during the COVID (Coronavirus disease)-19 pandemic, has caused shortages worldwide. This study aimed to examine the sterilization ability of the portable sterilizer prototype for N95 masks and its effect on the filtration ability and changes in air resistance on the N95 mask in order to thrift personal protective equipment (PPE) use during a shortage. The sample used was an N95 mask type 1860. The mask was contaminated with 0.6-0.8 MFU Staphylococcus aureus and Escherichia coli. The sterilization methods used were Ultraviolet Germicidal Irradiation (UVGI), Heat at 75°C, and a combination of both from 1 to 120 minutes. Next, the masks were cultured in a nutrient agar medium. For aerosol penetration and air resistance tests, masks were tested before and after the sterilization process, lasting from 5 to 60 minutes. This prototype sterilizer with Heat effectively killed E. coli and S. aureus starting from 3 minutes. The filtration ability of the N95 mask was maintained at >95% even after the sterilization process with 75°C heat, UVC, or a combination of both for up to 60 minutes. There was also no significant difference in air resistance between new masks and masks that had been sterilized using a portable sterilizer. This prototype sterilizer with Heat at 75°C can effectively sterilize against both gram-positive and negative bacteria in the N95 mask without reducing the aerosol filtration ability and changing the air resistance of the N95 mask.

Exposure to bacterial and fungal bioaerosols in facilities processing biodegradable waste.

The aim of the study was to determine the exposure of workers within biodegradable waste processing facilities to bacteria and fungi to identify any exposures of potential concern to health. Occupational measurements were performed in six composting and three bioenergy (bioethanol or methane/biogas) producing facilities. Bioaerosols were measured from breathing zones with Button aerosol or open face cassette filter samplers, and swab specimens were taken from the nasal mucous membranes of the workers. Aspergillus fumigatus, Bacillus cereus group, Campylobacter spp., Salmonella spp., Streptomyces spp., and Yersinia spp. were determined by real-time polymerase chain reaction (qPCR). A. fumigatus, and mesophilic and thermophilic actinobacteria were also cultivated from filters. Bacterial airborne endotoxins collected by IOM samplers were analyzed using a Limulus assay. Bioaerosol levels were high, especially in composting compared to bioenergy producing facilities. Endotoxin concentrations in composting often exceeded the occupational exposure value of 90 EU/m3, which may be harmful to the health. In addition to endotoxins, the concentrations of A. fumigatus (up to 2.4 × 105 copies/m3) and actinobacteria/Streptomyces spp. (up to 1.6 × 106 copies/m3) in the air of composting facilities were often high. Microbial and endotoxin concentrations were typically highest in waste reception and pre-treatment, equal or decreased during processing and handling of treated waste, and lowest in wheel loader cabins and control rooms/outdoors. Still, the parameters measured in wheel loader cabins were often higher than in the control sites, which suggests that the use of preventive measures could be improved. B. cereus group, Salmonella spp., and Yersinia spp. were rarely detected in bioaerosols or nasal swabs. Although Campylobacter spp. DNA was rarely detected in air, as a new finding, Campylobacter ureolyticus DNA was frequently detected in the nasal mucous membranes of workers, based on partial 16S rDNA sequencing. Moreover, especially A. fumigatus and C. ureolyticus spp. DNA concentrations in swabs after the work shift were significantly higher than before the shift, which indicates their inhalation or growth during the work shift. Microbial qPCR analysis of bioaerosols and swab samples of nasal mucosa allowed measuring exposure in various work operations and during the work shift, identifying problems for health risk assessment to improve working conditions, and evaluating the effectiveness of preventive measures and personal protection of workers.

Investigation of the Possibility of Application of Metal Fibrous Media in the Process of Filtration of Liquid Aerosols

This manuscript presents a study of the possibility of applying metallic fibre filter media made of stainless steel for the filtration process of liquid aerosols. To perform the experiment, three types of filters were used: single layer and symmetric or non-symmetric multi-layered filters. Filters have been loaded with DEHS (Di-Ethyl-Hexyl-Sebacate) aerosol while the pressure drop and the collection efficiency were monitored. The impact of the filtration velocity on the saturation pressure drop has been quantified for monolayer filters. The building of a draining film on the free surface of the multi-layered filters has been studied and the impact of this phenomenon on the filtration performances and saturation ratio of the medium are discussed. For multilayer filters, the clogging dynamic, occurring by a successive loading of the draining layers, is highlighted in this work. Finally, propositions are made to evaluate the behaviour of metallic multi-layered filters for liquid aerosol filtration applications.

Development of graphitization method for low carbon aerosol filter samples with Automated Graphitization System AGE-3

The wide applications of the radiocarbon (14C) approach in environmental, archeological, and geological research often necessitates the analysis of microgram-sized samples. The ability to measure low carbon samples is particularly relevant for aerosol particle filters, especially for samples from pristine environments. For this purpose, we investigated the sample dilution method for graphitization of low-carbon samples (20–200 μg C) with an Automated Graphitization System (AGE-3), and applied a mass balance equation for the calculation of 14C values. Materials with known 14C values (standards NIST-OXII and IAEA-C7) were diluted with 14C-free phthalic anhydride (PhA) until sufficient mass (500 μg C) for graphitization with the AGE-3 system was acquired. Reliable 14C values were obtained for samples with carbon amount in the range of 40–200 μg. Next, we adapted the dilution method for estimation of aerosol sample 14C values. Using it, we attained a precision of 0.71 ± 0.83 pMC for 14C measurements of aerosol samples containing 40–200 μg C. A shift of radiocarbon values to 5.07 pMC (average 3.08 ± 1.7 pMC) was observed for samples with low carbon content (<20 μg C). We determined that a precision of 2–3 pMC is acceptable for aerosol particle source apportionment studies. Using the sample dilution method, graphitization with AGE-3 of aerosol samples with carbon content >40 μg becomes a viable and efficient way of sample preparation for 14C analysis.

Particle characterization and quantification of organic and inorganic compounds from Chinese and Iranian aerosol filter samples using scanning laser desorption/ionization mass spectrometry

Besides their influence on climate and cloud formation, many organic and inorganic substances in aerosol particles pose a risk to human health. Namely, polycyclic aromatic hydrocarbons (PAH) and heavy metals are suspected to be carcinogenic or acutely toxic. The detection and quantification of such compounds is difficult if only small amounts of particulate matter (PM) are available. In addition, filter samples are often complex and time-consuming to prepare for chromatographic measurements and elemental analysis. Here, we present a method based on high-resolution atmospheric pressure laser desorption ionization mass spectrometry imaging (AP-LDI-MSI) and statistical analysis which allows the analysis and characterization of very small sample quantities (< 30 µg) without any sample preparation. The power and simplicity of the method is demonstrated by two filter samples from heavily polluted mega cities. The samples were collected in Tehran (Iran) and Hangzhou (China) in February 2018. In the course of the measurement, more than 3200 sum formulae were assigned, which allowed a statistical evaluation of colocalized substances within the particles on the filter samples. This resulted in a classification of the different particle types on the filters. Finally, both megacities could be distinguished based on characteristic compounds. In the samples from Tehran, the number of sulphur-containing organic compounds was up to 6 times as high as the samples from Hangzhou, possibly due to the increasing efforts of the Chinese government to reduce sulphur emissions in recent years. Additionally, quantification of 13 PAH species was carried out via standard addition. Especially, the samples from Tehran showed elevated concentrations of PAHs, which in the case of higher-molecular-weight species (> m/z 228) were mostly more than twice as high as in Hangzhou. Both cities showed high levels of heavy metals and potentially harmful organic compounds, although their share of total particulate matter was significantly higher in the samples from Tehran. The pre-treatment of the samples was reduced to a minimum with this method, and only small amounts of particles were required to obtain a comprehensive picture for a specific filter sample. The described method provides faster and better control of air pollution in heavily polluted megacities.Graphical abstract