High-Resolution Fluorescence Spectra of Airborne Biogenic Secondary Organic Aerosols: Comparisons to Primary Biological Aerosol Particles and Implications for Single-Particle Measurements

Comprehensive insights into advances in ambient bioaerosols sampling, analysis and factors influencing bioaerosols composition

While the study of bioaerosols has a long history, it has garnered heightened interest in the past few years, focusing on both culture-dependent and independent sampling and analysis approaches. Observations have been made regarding the seasonal fluctuations in microbial communities and their connection to particular ambient atmospheric factors. The study of airborne microbial communities is important in public health and atmospheric processes. Nevertheless, the establishment of standardized protocols for evaluating airborne microbial communities and utilizing microbial taxonomy as a means to identify distinct bioaerosols sources and seasonal patterns remains relatively unexplored. This article discusses the challenges and limitations of ambient bioaerosols sampling and analysis, including the lack of standardized methods and the heterogeneity of sources. Future prospects in the field of bioaerosols, including the use of high-throughput sequencing technologies, omics studies, spectroscopy and fluorescence-based monitoring to provide comprehensive incite on metabolic capacity, and activity are also presented. Furthermore, the review highlights the factors that affect bioaerosols composition, including seasonality, atmospheric conditions, and pollution levels. Overall, this review provides a valuable resource for researchers, policymakers, and stakeholders interested in understanding and managing bioaerosols in various environments.

Regionally sourced bioaerosols drive high-temperature ice nucleating particles in the Arctic

Primary biological aerosol particles (PBAP) play an important role in the climate system, facilitating the formation of ice within clouds, consequently PBAP may be important in understanding the rapidly changing Arctic. Within this work, we use single-particle fluorescence spectroscopy to identify and quantify PBAP at an Arctic mountain site, with transmission electronic microscopy analysis supporting the presence of PBAP. We find that PBAP concentrations range between 10-3-10-1 L-1 and peak in summer. Evidences suggest that the terrestrial Arctic biosphere is an important regional source of PBAP, given the high correlation to air temperature, surface albedo, surface vegetation and PBAP tracers. PBAP clearly correlate with high-temperature ice nucleating particles (INP) (>-15 °C), of which a high a fraction (>90%) are proteinaceous in summer, implying biological origin. These findings will contribute to an improved understanding of sources and characteristics of Arctic PBAP and their links to INP.

Airborne Microbial Aerosol Detection by Combining Single Particle Mass Spectrometry and a Fluorescent Aerosol Particle Sizer

Detection methods for microbiological aerosols based on single particle mass spectrometry (SPAMS) and a fluorescent aerosol particle sizer (FLAPS) have been developed progressively. However, they encounter interference and inefficiency issues. By merging FLAPS and SPAMS technologies, the majority of inorganic ambient aerosols may be eliminated by the FLAPS, thus resolving SPAMS' large data volume. SPAMS, on the other hand, may eliminate the secondary fluorescence interference that plagues the FLAPS. With the addition of the enhanced machine learning classifier, it is possible to extract microbial aerosol signals more precisely. In this work, a FLAPS-SPAMS instrument and a Random Forest classifier based on Kendall's correlation expansion training set approach were built. In addition to analyzing the outdoor microbial proportions, the interference components of non-microbial fluorescent particles were also examined. Results indicate that the fraction of outdoor microbial aerosols in fluorescent particles is 25.72% or roughly 2.57% of total particles. Traditional ART-2A algorithm and semi-empirical feature clustering approaches were used to identify the interference categories of abiotic fluorescent particles, which were mostly constituted of EC/OC, LPG/LNG exhaust, heavy metal organics, nicotine, vinylpyridine, polycyclic aromatic hydrocarbons (PAHs), and polymers, accounting for 68.51% of fluorescent particles.

Biological and Nonbiological Sources of Fluorescent Aerosol Particles in the Urban Atmosphere

Online detection of bioaerosols based on the light-induced fluorescence (LIF) technique is still challenging due to the complexity of bioaerosols and the external/internal mixing with nonbiological fluorescent compositions. Although many lab studies have measured the fluorescence properties of the biological and nonbiological materials, there is still a scarcity of knowledge of the sources of fluorescent aerosol particles (FAP) in the ambient atmosphere. Here, we fill this gap by combining the online measurement of an LIF-based instrument (wideband integrated bioaerosol sensor, WIBS, 0.8-20 μm) with the measurements of typical biological matter and the compositions related to major nonbiological FAP from May to July in the megacity Beijing. We find that fungal spores and pollen are widely observed in all types of FAP using a WIBS. Bacteria are suggested to be associated with the fine mode FAP (excitation/emission: 280 nm/310-400 nm; 0.8-3 μm). The FL-B and -BC particles (emission in 420-650 nm) contributing the most to FAP are strongly associated with humic-like substances, dust, burning and combustion emissions, and secondary organic aerosols (SOA). This study provides a guide for interpreting individual FAP measured by LIF instruments and points to the applicability of online LIF instruments to characterize nonbiological compositions including SOA.