Airborne Biological Particles Research Articles

Saharan dust storms affecting the center of the Iberian Peninsula: Effect on the urban aerobiome

Dust storms are known to be atmospheric phenomena that transport mineral dust but also airborne biological particles (bioaerosols) from desert areas to distant regions. These bioaerosols can influence atmospheric processes and they have the potential of changing the composition of the local aerobiome in urban areas, which, in recent years, have been associated with allergies and the exacerbation of respiratory syndromes. Here, we studied four dust events initiated in the Sahara Desert affecting the center of the Iberian Peninsula. The biological particles before and during the phenomena were analyzed by high-throughput DNA sequencing. The global composition of bioaerosols showed a marked seasonality. The relative abundances of the most predominant groups of bacteria and fungi were not significantly altered compared to the days prior the corresponding event. Nonetheless, we detected specific bacterial and fungal taxa associated with these events, whose composition and abundance were also related to the period of the year. Although a variety of plant and animal pathogens were identified both before and throughout the days influenced by dust storms, some were only detected during the latter, suggesting a long-range transport for these species. This work highlights the importance of analyzing the storm dust events separately, especially when they occur at different seasons, and the particular effect on an urban environment in the Iberian Peninsula as a model case, providing some recommendations for future studies.

Maritime and continental microorganisms collected in Mexico: An investigation of their ice-nucleating abilities

Airborne biological particles have a great potential to affect the hydrological cycle as they have been reported as the most efficient ice nucleating particles (INPs). However, their spatiospatial-temporal variability and their ice nucleation abilities are highly uncertain. The present study reports the ice-nucleating abilities, via immersion freezing, of 32 bacteria, 6 fungi, and 26 marine phytoplankton species isolated in different environments in Mexico. Although 15 of the 56 evaluated microorganisms were found to trigger ice formation at temperatures above −21.5 °C, 41 species (i.e., 91% of the studied microorganisms) can be considered as inefficient INPs as their median freezing temperatures (T50) were observed to be below −25 °C. Only the Cupriavidus pauculus and the Phaeocystis sp. reported moderately warm T50 values, i.e., −17.3 °C and − 19.5 °C, respectively. This corroborates the hypothesis that only a very limited fraction of the bioaerosol population have the potential to impact ice formation within clouds, including those found in the Tropics. Finally, out of the three bioparticles studied, phytoplankton showed to be the most efficient INP, in terms of T50, while fungal propagules show the lowest potential to impact mixed-phase cloud formation because of their poor ice-nucleating abilities.

Characteristics and Impact Factors of Number Concentration of Primary Biological Aerosol Particles in Beijing

Primary biological aerosol particles (PBAP) are an important part of ambient aerosols. Both living and dead organisms not only influence human health and air quality but also play important roles in regulating certain atmospheric processes and affect the hydrological cycle and climate change. In this study, flow cytometry (FCM) was utilized in combination with the simultaneous use of permeant (SYBR Green I) and impermeant (propidium iodide, PI) nucleic acid fluorescent staining to detect and quantify the viable and dead airborne biological particles. At the same time, based on this method, the dead/viable PBAP in a Beijing urban area was detected and quantified. Moreover, the influence of environmental factors on the concentrations of primary biological aerosol particles was illuminated. The results showed that the media number concentration of dead and alive PBAP in the Beijing urban area during summer (1.03×106 m-3 and 7.43×105 m-3, respectively) were higher than those during winter (7.34×105 m-3and 6.18×105 m-3, respectively). Statistical analysis showed that there was no significant correlation between PBAP number concentration and environmental factors, i.e., meteorological conditions and air quality, showing a weak positive correlation with temperature and humidity and weak negative correlations with O3, maximum wind speed, and sunshine duration. The number concentration of PBAP was weakly correlated with the mass concentration of PM2.5 but positively correlated with that of coarse particulate matter (PM2.5-10). Both stable weather and dust transport could increase the number concentration of PBAP in Beijing.

Mass concentration measurements of autumn bioaerosol using low-cost sensors in a mature temperate woodland free-air carbon dioxide enrichment (FACE) experiment: investigating the role of meteorology and carbon dioxide levels

Abstract. Forest environments contain a wide variety of airborne biological particles (bioaerosols), including pollen, fungal spores, bacteria, viruses, plant detritus, and soil particles. Forest bioaerosol plays a number of important roles related to plant and livestock health, human disease and allergenicity, and forest and wider ecology and are thought to influence biosphere–atmosphere interactions via warm and cold cloud formation. Despite the importance of bioaerosols, there are few measurements of forest aerosol, and there is a lack of understanding of how climate change will affect forest bioaerosol in the future. We installed low-cost optical particle counters (OPCs) to measure particles in the size range between 1 and 10 µm (PM10–PM1) for a period of 2 months in autumn 2018 at the Birmingham Institute of Forest Research (BIFoR) free-air carbon dioxide enrichment (FACE) facility. In the paper, we propose that the PM10–PM1 (particulate matter) metric is a good proxy for bioaerosols because of the bioaerosol representative size range, the location of the study site (a woodland in a rural location), the field measurement taking place during the season of peak fungal activity, and the low hygroscopicity of the particles measured. The BIFoR FACE facility fumigates three 700 m2 areas of the forest with an additional 150 ppm CO2 above ambient levels with minimal impacts on other potential environmental drivers such as temperature, humidity, and wind. This experimental set-up enabled us to investigate the effect of environmental variables, including elevated CO2 (eCO2), on bioaerosol proxy concentrations and to evaluate the performance of the low-cost OPCs in a forested environment. Operating the low-cost OPCs during autumn 2018, we aimed to capture predominantly the fungal bioaerosol season. Across the experimental duration, the OPCs captured both temporal and spatial variation in bioaerosol concentrations. Aerosol concentrations were affected by changing temperatures and wind speeds but, contrary to our initial hypothesis, not by relative humidity. We detected no effect of the eCO2 treatment on total bioaerosol concentrations, but a potential suppression of high-concentration bioaerosol events was detected under eCO2. In-canopy atmospheric dispersion modelling indicates that the median spore dispersion distance is sufficiently small that there is little mixing between treatment and control experiments. Our data demonstrate the suitability of low-cost OPCs, interpreted with due caution, for use in forests and so opens the possibility of forest bioaerosol monitoring in a wider range of habitats to a wider range of researchers at a modest cost.

The characterization and quantification of viable and dead airborne biological particles using flow cytometry and double fluorescent staining

Primary biological aerosol particles (PBAPs) are important air pollutants because they are ubiquitous in the atmosphere; influence human health, air quality, atmospheric chemistry and physics; and play important roles in regulating atmospheric processes. In investigations of the effects of PBAPs in ambient environments, it is necessary to distinguish them from other particles. In this study, flow cytometry (FCM) was utilized in combination with permeant (SYBR Green dyes) and impermeant (Propidium Iodide, PI) nucleic acid fluorescent stains, to characterize and quantify the viable and dead airborne PBAPs in ambient aerosol in Beijing, China. The number concentrations of viable and dead PBAPs showed a consistent trend and correlated well with one another (R2 = 0.72, p < 0.01). However, no relationship was found between the number concentration of PBAPs and non-biological particles. The mean number concentrations of total particulate matter, dead PBAPs and viable PBAPs were 5.78 × 106 m−3, 1.11 × 106 m−3 and 7.09 × 105 m−3, respectively. The median PBAPs number concentrations (the sum of dead and viable) exhibited a seasonal cycle, i.e., highest in summer and autumn, lowest during winter and spring. Despite a lower median PBAPs number concentration during winter compared with other seasons, the viability peaked during winter, coinciding with the winter flu season. Stable synoptic conditions, polluted southwesterly air mass and long-range transported dust from the northwest desert region all contributed to the occurrence of explosive fluorescent PBAP episodes in Beijing, China.

Bioaerosols and dust are the dominant sources of organic P in atmospheric particles

Several studies assessed the impact of inorganic P in fertilizing oligotrophic areas, however, the importance of organic P in such fertilization processes received far less attention. In this study, the amount and origin of organic P delivered to the eastern Mediterranean Sea were characterized in atmospheric particles using the positive matrix factorization model (PMF). Phospholipids together with other chemical compounds (sugars, metals) were used as tracers in PMF. The model revealed that dominant sources of organic P are bioaerosols and dust. The amount of organic P from bioaerosols (~4 Gg P y−1) is similar to the amount of soluble inorganic P originating from dust aerosols; this is especially true during highly stratified periods when surface waters are strongly P-limited. The deposition of organic P from bioaerosols can constitute a considerable flux of bioavailable P—even during periods of dust episodes, implying that airborne biological particles can potentially fertilize marine ecosystems.

Plant biodiversity assessment through pollen DNA metabarcoding in Natura 2000 habitats (Italian Alps)

Monitoring biodiversity is of increasing importance in natural ecosystems. Metabarcoding can be used as a powerful molecular tool to complement traditional biodiversity monitoring, as total environmental DNA can be analyzed from complex samples containing DNA of different origin. The aim of this research was to demonstrate the potential of pollen DNA metabarcoding using the chloroplast trnL partial gene sequencing to characterize plant biodiversity. Collecting airborne biological particles with gravimetric Tauber traps in four Natura 2000 habitats within the Natural Park of Paneveggio Pale di San Martino (Italian Alps), at three-time intervals in 1 year, metabarcoding identified 68 taxa belonging to 32 local plant families. Metabarcoding could identify with finer taxonomic resolution almost all non-rare families found by conventional light microscopy concurrently applied. However, compared to microscopy quantitative results, Poaceae, Betulaceae, and Oleaceae were found to contribute to a lesser extent to the plant biodiversity and Pinaceae were more represented. Temporal changes detected by metabarcoding matched the features of each pollen season, as defined by aerobiological studies running in parallel, and spatial heterogeneity was revealed between sites. Our results showcase that pollen metabarcoding is a promising approach in detecting plant species composition which could provide support to continuous monitoring required in Natura 2000 habitats for biodiversity conservation.

Single-particle optical-trapping Raman spectroscopy for the detection and identification of aerosolized airborne biological particles

The detection and identification of bioaerosol particles, especially a potential threat from aerosolized biowarfare agents (BWAs), has become increasingly important. Here, we report on single-particle optical-trapping Raman spectroscopy (OT-RS) for the detection and identification of airborne biological particles. OT enables the capture of single particles in air for several minutes or longer, more than sufficient to capture the Raman spectra and minimize the interference from background aerosol particles. Simultaneously, the embedded imaging system can provide real-time information on the shape and size of the trapped particles. Several kinds of bioaerosol particles were analyzed using OT-RS including four BWA surrogates: Bacillus globigii, Yersinia rhodei, MS2, and Bacillus subtilis, along with some interfering bioaerosol particles commonly presented in the atmosphere. Similarities and differences of the Raman spectra of these biological particles are discussed. In addition, the BWA surrogates are well classified by using the principal component analysis. The results demonstrate that single-particle OT-RS can be used not only for the potential detection of BWAs but also for the identification of BWAs.

Biodegradation and Microbial Contamination of Limestone Surfaces: An Experimental Study from Batalha Monastery, Portugal

An experimental study was conducted to assess the nature and extent of the biodeterioration of the limestone in the Batalha Monastery in Portugal. Stone fragments covered with microbial biofilms and lichenous crusts were investigated using Optical Microscopy (OM), Low Vacuum Scanning Electron Microscopy with Energy Dispersive Spectroscopy (LV-SEM + EDS), and X-ray micro-Diffractometry (μ-XRD). Microbial samples were collected from the stone surface, cultured, and analyzed with NGS metagenomic DNA test to classify the bacterial communities associated with the formation of the biofilms. Particulate air pollutants collected on Pall GN-6 paper filters using a cascade impactor were characterized by SEM-EDS + NGS. The results showed that lichens play a major role in biodeterioration by promoting both physical and chemical attack on the limestone substrate via hyphae mechanical penetration along calcite inter-crystalline spaces, the dissolution/leaching of calcite minerals, and the precipitation of secondary minerals such as Ca-oxalates within the stone porosity framework. DNA analyses identified the bacterial communities within the biofilms and their relative abundances. Air quality monitoring results suggest that the microbial population colonizing the monastery limestone could at least partially be derived from the dry and wet deposition of airborne biological particles on the stone surfaces and that S, N, and P-rich air pollutants may have provided nutrients and energy for the bacteria communities, thus indirectly facilitating biofilm formation, the growth of a lichenous crusts, and limestone biodeterioration effects.

An important challenge in occupational health: sampling indoor airborne viruses

Airborne biological particles are made by bacteria, viruses, fungi, pollen, dust mites and other living organisms. Between the airborne biological contaminants, the sampling of airborne viruses is the most difficult. This technical challenge has real consequences both in limiting the studies on the aerobiology of viral diseases, and in making possible, at least for now, to establish Standards for Acceptable Bioaerosol Exposure Limits in case of viruses. The circumstances and uncertainties in which we are living from the end of 2019, have demonstrated once again, the need of having common approaches in sampling, processing, and analysis of bioaerosol samples. Results from sampling indoor airborne viruses can be used both for identifying the airborne transmission of the respiratory viruses and for providing useful information as support in human health risk assessments. On the other hand, even if there are different sampling methods and equipment used for collecting bioaerosols, there are certain elements that must be considered in choosing the most appropriate sampling method to collect airborne viruses. The main challenge in sampling indoor airborne viruses is to identify the system that allows the sampling of bioaerosols ensuring in the same time the viability of the virus and the representativeness of the sample. Keeping in mind the lack of standardization in sampling indoor airborne viruses, as well as the missing of common approaches for air sampling strategies or sample treatment and analysis, the present work is focused on providing important recommendations as support in the concentrated effort of the researchers in developing of a common strategy for indoor viable bioaerosol sampling for virus detection.

Distribution of airborne pollen, fungi and bacteria at four altitudes using high-throughput DNA sequencing

The diversity and composition of bioaerosols in the atmosphere have been studied in the recent years in multiple places and under very different meteorological conditions. Pollen grains, fungal propagules and bacteria are the most studied airborne biological particles, usually individually, and correlated to environmental factors such as temperature, wind speed, rain, air pollution, etc. to understand their influence. However, the effect of the height on the distribution and composition of these bioaerosols has not been properly described so far. In this research, we analyzed concurrently these three biological particles at four different heights (1.5 m, 130 m, 500 m and 1000 m) by high-throughput DNA sequencing. We observed that the atmosphere contains a homogeneous distribution and composition of biological particles regardless of the altitude tested. Only a minority of the taxa is differently distributed. Therefore, we here deduce that the altitude does not drastically influence the airborne bioparticles distribution and composition under similar meteorological conditions. We also studied the co-occurrence between different bioaerosols, finding new potential relationships.

The Differential Vertical Distribution of the Airborne Biological Particles Reveals an Atmospheric Reservoir of Microbial Pathogens and Aeroallergens.

The most abundant biological particles present in the air are bacteria, fungal propagules and pollen grains. Many of them are proved allergens or even responsible for airborne infectious diseases, which supports the increase of studies in recent years on their composition, diversity, and factors involved in their variability. However, most studies in urban areas are conducted close to ground level and a factor such as height is rarely taken into account. Thus, the information about how the composition of biological particles changeswith this variable is scarce. Here, we examined the differential distribution of bacteria, fungi, and plants at four altitudes (up to ∼ 250m) in a metropolitan area using high-throughput DNA sequencing. Most taxa were present at all levels (common taxa). However, a transitional layer between 80 and 150m seemed to affect the scattering of these bioaerosols. Taxa not present at all altitudes (non-common) showed an upward tendency of diversity for bacteria and plants with height, while the opposite trend was observed for fungi. Certain patterns were observed for fungi and specific plant genera, while bacterial taxa showed a more arbitrary distribution and no patterns were found. We detected a wide variety of aeroallergens and potential pathogens at all heights, which summed a substantial portion of the total abundance for fungi and plants. We also identified potential connections between the biological particles based on their abundances across the vertical section.

Development of a real-time handheld bioaerosol monitoring system using ultraviolet-light emitting diode induced fluorescence

A handheld biological particle monitoring system that analyzes airborne biological particles in real time was designed, fabricated and its performance was investigated. An ultraviolet-light emitting diode (UV-LED) light source with a 280-nm wavelength was used. The design of an optical module that is composed of an ultraviolet source, a nozzle and flow controller, an ultraviolet cell, and a detection region was described. Through performance measurements, it was confirmed that scattering signals that corresponded to each particle size were measured, and that the proposed system effectively distinguished biological particles from non-biological components. It is expected that the proposed system can be applied to various biological particle and environment monitoring systems.

Environmental impact assessment of Pinaceae airborne pollen and green infrastructure using BIM

Abstract Urban air quality is a parameter that plays a major role in human health at the local scale. Consequently, in urban planning, the behavior and potential risk of allergenicity for some pollen grains coming from ornamental trees and green spaces surrounding newly built buildings, should be considered. This paper aims to study how pollen exposure, influenced by weather parameters, can be assessed and integrated in the designing and building of constructions as other component of air quality assessment beforehand, by using BIM. Based on a comparative aerobiological study at the height over a building (sampled by two traps at ground and at 16 m), a 3D local dynamic parametric scenario was modelled using BIM, and hourly average Pinaceae pollen concentrations (due to the closeness of pine trees to the samplers). From continuous recording (2009–2011) influenced by height and the influence of wind direction and speed was analysed. Additionally, a map of pine trees geolocated around the studied building was produced and the hourly average Pinaceae pollen concentrations were represented by Revit. BIM together with aerobiology can be a novel and useful tool for the construction of buildings considering airborne biological particles. This represents a first step towards the integration of some unusual environmental parameters in urban planning. Pollen grains modelling as an environmental health criterion for the construction of new buildings will allow technicians to avoid possible future isolation points in the design of building envelopes, and high pollen exposure rates could be avoided, creating ‘allergy-free’ buildings.

Biological airborne particles in Kırsehır atmosphere except for pollen and fungal spores

Aerobiology is a branch of biology that examines biological particles found both in the outdoor and indoor air. People's daily lives are influenced by these airborne biological particles in the air. Many people in society show an allergic reaction to these allergic airborne particles. A significant portion of the world's population reacts with airborne particles inhaled in various forms. The severity of these reactions varies with the degree of exposure to these particles over time and the concentration of the inhaled particles. In this study, for two years it has been investigated that biological particles (fungal hyphal fragments, pteridophyte spores, plant hairs, insect, insect extremities, moth scales, diatom etc. except for pollen and fungal spores) of Kirsehir atmosphere by using Burkard 7-day air sampler. In total, 4674 particles in 2015, and 5262 biological particles in 2016, have been counted

Recommended terminology for aerobiological studies

Aerobiology is an interdisciplinary science where researchers with different backgrounds are involved in different topics related to microorganism, airborne biological particles, e.g. pollen and spores, and phenology. Some concepts, words or expressions used in aerobiology have a clear definition, but are however frequently misused. Therefore, the working group “Quality Control” of the European Aerobiology Society (EAS) and the International Association of Aerobiology (IAA) would like to clarify some of them, their use and presentation.

Seasonal variability in size-segregated airborne bacterial particles and their characterization at different source-sites.

Size-segregated aerosol samplings were carried out near the potential sources of airborne biological particles i.e. at a landfill site, an agricultural field and a road side restaurant-cluster site in winter, spring and summer seasons during 2013-2015 in New Delhi. The culturable airborne bacterial (CAB) concentrations showed significant seasonal variation from higher to moderate in spring and winter seasons and lowest during summer. Highest CAB concentrations were observed at the Okhla landfill site followed by restaurant-cluster area and agriculture site. The CAB particles showed bimodal size distribution, abundant in the size ranges of 1.1-2.1, 2.1-3.3 and 4.7-5.8μm. However, substantial concentrations were also observed in the size bins of 0.43-0.65 and <0.43μm, which are important for cloud condensation nuclei (CCN) activity of aerosols in addition to their adverse health effects. In spring, bacterial particles were also maximized in size ranges between 5.8 and >9.0μm. Fine mode proportions of CAB were found to be higher in winter than other two seasons. Bacterial identification was done by 16s rDNA sequencing, and most abundant identified strains were Bacillus cereus (16%), Bacillus licheniformis (11%), Bacillus thuringiensis (9%), Micrococcus sp. (7%) and Acinetobacter sp. (9%).

Evaluation of machine learning algorithms for classification of primary biological aerosol using a new UV-LIF spectrometer

Abstract. Characterisation of bioaerosols has important implications within environment and public health sectors. Recent developments in ultraviolet light-induced fluorescence (UV-LIF) detectors such as the Wideband Integrated Bioaerosol Spectrometer (WIBS) and the newly introduced Multiparameter Bioaerosol Spectrometer (MBS) have allowed for the real-time collection of fluorescence, size and morphology measurements for the purpose of discriminating between bacteria, fungal spores and pollen.This new generation of instruments has enabled ever larger data sets to be compiled with the aim of studying more complex environments. In real world data sets, particularly those from an urban environment, the population may be dominated by non-biological fluorescent interferents, bringing into question the accuracy of measurements of quantities such as concentrations. It is therefore imperative that we validate the performance of different algorithms which can be used for the task of classification.For unsupervised learning we tested hierarchical agglomerative clustering with various different linkages. For supervised learning, 11 methods were tested, including decision trees, ensemble methods (random forests, gradient boosting and AdaBoost), two implementations for support vector machines (libsvm and liblinear) and Gaussian methods (Gaussian naïve Bayesian, quadratic and linear discriminant analysis, the k-nearest neighbours algorithm and artificial neural networks).The methods were applied to two different data sets produced using the new MBS, which provides multichannel UV-LIF fluorescence signatures for single airborne biological particles. The first data set contained mixed PSLs and the second contained a variety of laboratory-generated aerosol.Clustering in general performs slightly worse than the supervised learning methods, correctly classifying, at best, only 67. 6 and 91. 1 % for the two data sets respectively. For supervised learning the gradient boosting algorithm was found to be the most effective, on average correctly classifying 82. 8 and 98. 27 % of the testing data, respectively, across the two data sets.A possible alternative to gradient boosting is neural networks. We do however note that this method requires much more user input than the other methods, and we suggest that further research should be conducted using this method, especially using parallelised hardware such as the GPU, which would allow for larger networks to be trained, which could possibly yield better results.We also saw that some methods, such as clustering, failed to utilise the additional shape information provided by the instrument, whilst for others, such as the decision trees, ensemble methods and neural networks, improved performance could be attained with the inclusion of such information.

A new method for the real-time quantification of airborne biological particles using a coupled inertial aerosol system with in situ fluorescence imaging

We describe the integration of an aerosol inertial impactor with in situ fluorescence imaging for the real-time detection and monitoring of airborne biological particles. Airborne particles were continuously collected on a fluorescent dye-containing agarose gel, and a mini-fluorescence microscope was used to produce in situ fluorescence particle images. Concentrations of size-segregated and dye-stained particles were then measured in real time upon deposition of airborne biological particles on the agarose gel substrate. To evaluate system performance, airborne bacterial particles from Escherichia coli were introduced onto the impactor (termed Bio-impactor) at various air flow rates and collection times. The particle cut-off diameter (d50) was controlled by adjusting sample flow rate so that a sample flow rate of 10L/min produced a d50 of ∼0.84μm, which efficiently collected airborne E. coli particles. Our Bio-impactor system allows for the automated fluorescence imaging of collected particles, providing in situ information about fluorescence intensity at regular time intervals. We compared results from our system with those obtained using a colony counting method; our results demonstrated a clear correlation (R2=0.9536) between system response and expected particle counts. Our novel impactor system could provide an inexpensive, simple, and portable method of real-time bioaerosol quantification.

Rupturing of Biological Spores As a Source of Secondary Particles in Amazonia.

Airborne biological particles, such as fungal spores and pollen, are ubiquitous in the Earth's atmosphere and may influence the atmospheric environment and climate, impacting air quality, cloud formation, and the Earth's radiation budget. The atmospheric transformations of airborne biological spores at elevated relative humidity remain poorly understood and their climatic role is uncertain. Using an environmental scanning electron microscope (ESEM), we observed rupturing of Amazonian fungal spores and subsequent release of submicrometer size fragments after exposure to high humidity. We find that fungal fragments contain elements of inorganic salts (e.g., Na and Cl). They are hygroscopic in nature with a growth factor up to 2.3 at 96% relative humidity, thus they may potentially influence cloud formation. Due to their hygroscopic growth, light scattering cross sections of the fragments are enhanced by up to a factor of 10. Furthermore, rupturing of fungal spores at high humidity may explain the bursting events of new particle formation in Amazonia.