Characterization of organic species and functional groups in pollen, fungi, algae, and bacteria bioaerosols†

Though the importance of bioaerosols is increasing with the changing climate, very little is known about the chemistry of bioaerosols, their atmospheric fate, and chemical composition. This paper is focused on the characterization of chemical functional groups of four atmospherically relevant bioaerosols: pollen (lodgepole pine and rabbitbrush), fungi (western gall rust), bacteria (Pedobacter and hay bacillus), and algae (spirulina). For this purpose, the proton nuclear magnetic resonance (¹H-NMR) technique was used on water-soluble extracts of the selected bioaerosols, while quantitative analysis of individual organic species (saccharides, amino acids, and fatty acids) was performed using gas chromatography mass spectrometry (GC-MS), ultra-high performance liquid chromatography (UPLC-MS), and UV-Vis-NIR (ultraviolet-visible-infrared) spectrophotometry. The obtained ¹H-NMR results revealed major contributions from aliphatic protons in Bacillus (50.2%) and Pedobacter (57.0%) bacteria, western gall rust fungus (39.7%), spirulina algae (73.8%), and rabbitbrush pollen (31.3%). Protons from saccharides were dominant in lodgepole pine pollen (27.6%). The quantitative analysis shows that the saccharide glucose is common among the analyzed bioaerosols, as well as proline, leucine, isoleucine, alanine, and phenylalanine amino acids, and palmitic, oleic, linoleic, linolenic, and stearic fatty acids (except in Bacillus bacteria). Concentrations of analyzed saccharides ranged between 2.01 μg mg⁻¹ of dry mass (in Bacillus bacteria) and 183.54 μg mg⁻¹ (in lodgepole pine pollen), followed by amino acids (from 2.57 μg mg⁻¹ in western gall rust fungus to 21.38 μg mg⁻¹ in Bacillus bacteria), and fatty acids (from 0.05 μg mg⁻¹ in Bacillus bacteria to 25.82 μg mg⁻¹ in lodgepole pine pollen). Comparison of ¹H-NMR and quantitative analyses showed a good correlation (R² = 0.608) between the saccharide segment of ¹H-NMR bioaerosol spectra and individual saccharide analysis.