The real-time monitoring of primary biological aerosol particles (PBAP) such as pollen and fungal spores has received much attention in recent years as a result of their health and climatic effects. In this study, the Wideband Integrated Bioaerosol Sensor (WIBS) 4+ model was evaluated for its ability to sample and detect ambient fungal spore and pollen concentrations, compared to the traditional Hirst volumetric method. Although the determination of total pollen and fungal spore ambient concentrations are of interest, the selective detection of individual pollen/fungal spore types are often of greater allergenic/agricultural concern. To aid in this endeavour, modifications were made to the WIBS-4 instrument to target chlorophyll fluorescence. Two additional fluorescence channels (FL4 and FL5 channels) were combined with the standard WIBS channels (FL1, FL2, FL3). The purpose of this modification is to help discriminate between grass and herb pollen from other pollen. The WIBS-4+ was able to successfully detect and differentiate between different bioaerosol classes. The addition of the FL4 and FL5 channels also allowed for the improved differentiation between tree (R² = 0.8), herbaceous (R² = 0.6) and grass (R² = 0.4) pollen and fungal spores (R² = 0.8). Both grass and herbaceous pollen types showed a high correlation with D type particles, showing strong fluorescence in the FL4 channel. The additional fluorescent data that were introduced also improved clustering attempts, making k-means clustering a comparable solution for this high-resolution data.

Airborne fungal spores (AFS) represent the major fraction of primary biological aerosol particles (PBAPs), and they are studied worldwide largely due to their important role within the Earth system. They have an impact on climate and human health, and they contribute to the propagation of diseases. As their presence in the air depends largely on studied ecosystems, a spore trap was used to monitor their atmospheric concentrations from 2014 to December 2018 in Saclay, a suburban area in the megacity of Paris. The main objective of this work was: (1) to understand the atmospheric variability of AFS in relation to different variables such as meteorological factors, agricultural practice, and (2) to identify their geographical origin by using a source receptor model. During our period of observation, 30 taxa have been identified under a light microscope. In order of importance, Ascospores, Cladosporium, Basidiospores, Tilletiopsis, Alternaria were found to be the most abundant types respectively (50.8%, 33.6%, 7.6%, 1.8%, and 1.3%) accounting for 95% of the atmospheric concentrations. We observed a general decrease associated with a strong interannual variability. A bimodal seasonal cycle was identified with a first maximum in July and a second in October. The main parameters driving the atmospheric concentration are temperature and precipitation. The daily variability is strongly activated by successive periods of hot weather and rainfall, multiplying the concentration by a factor of 1000 in less than 12 hours. Results from the source receptor model ZeFir point out unambiguous different origins of AFS due to specific sources impacting the observation site. Our study also indicated that a hydrological stress has a direct effect on the daily concentrations. This last point should be taken into account for every stressed ecosystem studied in a global warming context. This is particularly important for Mediterranean areas where water is a key control of the growth and dispersion of fungal spores.

The study of the origin and dispersion processes associated with airborne pollen grains are important to understand due to their impacts on health. In this context, a Hirst-type spore trap was utilized over the period 2015–2018 to monitor ambient pollen grains at Saclay, France, a receptor site influenced by both clean air masses originating from the Atlantic Ocean and polluted air masses under anticyclonic conditions. The objective of this work was to use ZeFir (a user-friendly, software tool recently-developed to investigate the geographical origin and point sources of atmospheric pollution) as a method to analyse total and allergenic airborne pollen grain concentrations. Strong interannual variability was exhibited for the total pollen grains concentrations and it was determined that this was mainly driven by Betulaceae pollen, with a general increasing trend displayed. The start of the pollen season was seen to be triggered by particular synoptic conditions after a period of dormancy and two maximums were displayed, one in April and a second in June. Results from the ZeFir tool, fed with on-site hourly meteorological and pollen measurements, demonstrate that the dominant pollen grains inputs to Saclay are favoured by non-prevailing winds originating from East and North in association with dry air, moderate winds, mild temperature and enhanced insolation.

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.

Croplands remain poorly studied ecosystems in terms of total hydroxyl radical (OH) reactivity, especially when compared to forests. As part of the COV³ER project, total OH reactivity (ROH), defined as the total loss rate of OH due to its reaction with reactive species in the atmosphere, was characterized in a rapeseed field (Grignon, France) during the blooming season in April 2017. Measurements were performed in a dynamic chamber as well as in ambient air using the Comparative Reactivity Method (CRM). Complementary measurements of organic (including a proton transfer reaction quadrupole ion–time of flight mass spectrometry, PTRQi-ToFMS) and inorganic compounds were also performed in order to calculate the expected OH reactivity and evaluate the missing fraction. Measured ROH varied diurnally in the dynamic chamber (mROH_chamber) with maxima around 20 to 30 s⁻¹ at midday and minima during dark hours, following the variability of the enclosed branch VOCs_rapeseed, which is light- and temperature-dependent. Oxygenated VOCs were the major compounds emitted by the rapeseed crop. However, in terms of contribution to OH reactivity, isoprene accounted for 40% during the daytime, followed by acetaldehyde (21%) and monoterpenes (18%). The comparison between mROH_chamber and calculated ROH (cROH_chamber) exhibited little or no difference during dark hours, whereas a maximum difference appeared around midday, highlighting a significant missing fraction (46% on average during daytime) mainly related to biogenic temperature- and/or light-dependent emissions.

Background: The monitoring of bioaerosol concentrations in the air is a relevant endeavor due to potential health risks associated with exposure to such particles and in the understanding of their role in climate. In this context, the atmospheric concentrations of bacteria were measured from January 2018 to May 2020 at Saclay, France. The aim of the study was to understand the seasonality, the daily variability, and to identify the geographical origin of airborne bacteria. Methods: 880 samples were collected daily on polycarbonate filters, extracted with purified water, and analyzed using the cultivable method and flow cytometry. A source receptor model was used to identify the origin of bacteria. Results: A tri-modal seasonality was identified with the highest concentrations early in spring and over the summer season with the lowest during the winter season. Extreme changes occurred daily due to rapid changes in meteorological conditions and shifts from clean air masses to polluted ones. Conclusion: Our work points toward bacterial concentrations originating from specific seasonal-geographical ecosystems. During pollution events, bacteria appear to rise from dense urban areas or are transported long distances from their sources. This key finding should drive future actions to better control the dispersion of potential pathogens in the air, like persistent microorganisms originating from contaminated areas.