Urban enhancement of PM sub(10) bioaerosol tracers relative to background locations in the Midwestern United States

• Published in: Journal of geophysical research. Atmospheres 2016-05, Vol.121 (9), p.5071-5089
• Main Authors: Rathnayake, Chathurika M, Metwali, Nervana, Baker, Zach, Jayarathne, Thilina, Kostle, Pamela A, Thorne, Peter S, O'Shaughnessy, Patrick T, Stone, Elizabeth A
• Format: Article
• Language: English
• Subjects: Bacteria; Bioaerosols; Endotoxins; Fungi; Glucan; Proteins; Tracers; Urban areas
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1002/2015JD024538

Bioaerosols are well-known immune-active particles that exacerbate respiratory diseases. Human exposures to bioaerosols and their resultant health impacts depend on their ambient concentrations, seasonal and spatial variation, and copollutants, which are not yet widely characterized. In this study, chemical and biological tracers of bioaerosols were quantified in respirable particulate matter (PM sub(10)) collected at three urban and three background sites in the Midwestern United States across four seasons in 2012. Endotoxins from Gram-negative bacteria (and a few Gram-positive bacteria), water-soluble proteins, and tracers for fungal spores (fungal glucans, arabitol, and mannitol) were ubiquitous and showed significant seasonal variation and dependence on temperature. Fungal spores were elevated in spring and peaked in summer, following the seasonal growing cycle, while endotoxins peaked in autumn during the row crop harvesting season. Paired comparisons of bioaerosols in urban and background sites revealed significant urban enhancements in PM sub(10), fungal glucans, endotoxins, and water-soluble proteins relative to background locations, such that urban populations have a greater outdoor exposure to bioaerosols. These bioaerosols contribute, in part, to the urban excesses in PM sub(10). Higher bioaerosol mass fractions in urban areas relative to background sites indicate that urban areas serve as a source of bioaerosols. Similar urban enhancements in water-soluble calcium and its correlation with bioaerosol tracers point toward windblown soil as an important source of bioaerosols in urban areas. Key Points * PM sub(10), fungal glucans, bacterial endotoxins, and proteins are significantly enhanced in urban areas * Enhanced bioaerosol mass fractions point to urban areas as a source of some bioaerosol types * Correlations with calcium imply that dust and soil are major sources of bioaerosols in urban areas