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Bacterial aerosols are bacteria that are suspended in the atmosphere. We know very little about what typical bacterial aerosol communities are and the degree to which bacterial aerosols can cause disease if inhaled. Previous research has provided evidence that faecal matter from animals plays a dominant role in urban aerosols. One potential source for faecal bacterial aerosols is the aerosolization of waters contaminated with sewage. Aerosols are created from surface water through wind-wave interactions, wave-shore interactions and bubbles rising through the water column. Researchers from CUNY Queens College collected air and water samples from several highly urbanized waterfronts in New York City, including Newtown Creek, Flushing Bay, and Louis Valentino Pier. Newtown Creek, a Superfund site that is a tributary of the East River, and Flushing Bay, a tidal embayment in Queens, receives high levels of sewage through Combined Sewer Overflow releases. Louis Valentino Pier, on the New York Harbor, served as a less-contaminated comparison. Samples were also taken directly from a combined sewer overflow, which contained a mixture of raw sewage and stormwater about to be released into Flushing Bay.
I hypothesized that sewage-polluted surface water is a primary source of the sewage bacteria in the air. To establish this connection, I first confirmed previous findings that there are higher levels of sewage-associated bacteria in the water at Flushing Bay than in other urban waterbodies. Given this finding, I expected the aerosols at Flushing Bay to have higher levels of sewage-associated bacteria than Newtown Creek and Louis Valentino Pier aerosols. Additionally, the environmental parameters that affect aerosol production from surface waters, particularly wind speed and direction, should mediate the degree of similarity between surface water and aerosol communities.
To test these predictions, I analyzed the ecology of the bacterial communities in air and water samples using 454 pyrosequencing data from the bacterial 16S rRNA gene. I determined which samples were most similar and how environmental parameters, including wind speed, wind direction, aerosol count, and temperature, affected community composition. I found 29% of the CSO library and only 1% of the sediment library was associated with sewage. Sewage-associated bacteria in both water and air accounted for 5% of the bacterial community, suggesting that a connection between water and air is likely. Water samples from Flushing Bay had the highest percentage of sewage-associated bacteria, significantly more than the two other sites. The amount of sewage infrastructure bacteria in aerosols was similar across sites, but Newtown Creek had higher levels of fecal bacteria in both air and water samples. However, due to the small sample sizes, these results were not statistically significant. The most abundant bacterial types in the aerosols library across sites were Paracoccus (2.78%), Massilia (2.61%), Planococcus (2.52%), and Arthrobacter (2.01%). The most abundant bacterial types in the water sample library were Arcobacter (3.27%), Polaribacter (2.03%), Sulfurovum (2%), Flavobacterium (1.91%), and Sulfitobacter (1.66%). The most abundant bacteria in the CSO library were Arcobacter (14.64%), Acidovorax (8.68%), Tolumonas (7.41%), and Cloacibacterium (7.03%). The differences in dominant bacteria among water, air and CSO sample suggest that aerosols are produced from multiple sources, and local water sources may not be the primary source for all aerosols. However, this connection may be strengthened at higher wind speeds. Wind speed correlated with a higher number of shared species between water and air samples taken at the same time (R2=0.60 and p=0.042). Also, the single aerosol sample taken when wind was blowing over aeration ponds at a wastewater treatment plant had an order of magnitude more coarse aerosols than any other aerosol sample. It also clustered most closely with the CSO samples on a community similarity tree. These findings suggest that, while there is a connection between surface waters and aerosols in the urban environment, environmental parameters including wind speed and wind direction may modulate that interaction. Future areas of research include tracking aerosol creation and transport from wastewater treatment processes and higher resolution aerosol sampling to further resolve the water-air microbial connection.
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French, Shaya Regina, "Influence of sewage and sewage infrastructure on microbial aerosols above an urban waterway" (2015). Senior Projects Spring 2015. 235.