Atmospheric chemistry of bioaerosols: heterogeneous and multiphase reactions with atmospheric oxidants and other trace gases

Abstract

Advances in analytical techniques and instrumentation have now established methods for detecting, quantifying, and identifying the chemical and microbial constituents of particulate matter in the atmosphere. For example, recent cryo-TEM studies of sea spray have identified whole bacteria and viruses ejected from ocean seawater into air. A focal point of this perspective is directed towards the reactivity of aerosol particles of biological origin with oxidants (OH, NO₃, and O₃) present in the atmosphere. Complementary information on the reactivity of aerosol particles is obtained from field investigations and laboratory studies. Laboratory studies of different types of biologically-derived particles offer important information related to their impacts on the local and global environment. These studies can also unravel a range of different chemistries and reactivity afforded by the complexity and diversity of the chemical make-up of these particles. Laboratory experiments as the ones reviewed herein can elucidate the chemistry of biological aerosols.

Fig. 1. Oceans, covering >70% of Earth's surface, are a major source of biologically-derived compounds in the atmosphere. The biological, chemical, and physical processes in oceans affects the major chemical composition of sea-spray aerosol emitted into the atmosphere.

Fig. 2. Bright field TEM images of SSA prepared by cryo-TEM showing (a) a whole bacterium inside a wet SSA droplet, (b) a diatom, (c) a virus particle, and (d) marine membrane vesicles. Yellow arrows indicate the edge of the SSA, the red arrows indicate contamination from the cryo-TEM preparation, and the green arrows indicate the biological particles. Adapted with permission from Patterson et al., ACS Cent. Sci., 2016, 2, 40–47.

Fig. 3. Structures of OPPC, POPC and DPPC, shown on the surface of solid NaCl. Adapted with permission from Dilbeck et al., Phys. Chem. Chem. Phys., 2013, 15, 9833–9844.

Fig. 4. Schematic of a reaction pathway of residues within the protein BSA following exposure to ozone and followed by nitrogen dioxide. Adapted with permission from Shiraiwa et al., Environ. Sci. Technol., 2012, 46, 6672–6680.

Fig. 5. Schematic overview of the most relevant reactions and intermediates for protein oligomerization upon exposure of protein to environmentally relevant O₃ concentrations. Reprinted from Kampf et al., Environ. Sci. Technol., 2015, 49, 10859–10886.

Fig. 6. Raman spectra showing reactivity of LPS before (blue) and after (red) exposure to HNO₃ acid. The yellow highlighted peaks represent the nitrate vibrational modes. Adapted with permission from Trueblood et al., J. Phys. Chem. A, 2016, DOI: 10.1021/acs.jpca.6b07023.

Fig. 7. Basic components of lipid A, one of the main components of LPS that could react with gas phase nitric acid. The phosphate and carboxylate sites are highlighted and are found in the lipid A and inner core oligosaccharide regions of LPS.

Armando D. Estillore

Jonathan V. Trueblood

Vicki H. Grassian