Influence of sewage and sewage infrastructure on microbial aerosols above an urban waterway
Previous research has highlighted microbial connections between the terrestrial and aquatic environments and air quality at the local scale. Understanding the ecological and public health implications of this local connection remains an understudied frontier in the emerging field of atmospheric biology. The air and water quality connection, specifically as it relates to the aerosolization of sewage-associated bacteria in contaminated urban environments, is particularly understudied. Processes including wind-wave interactions, wave-shore interactions, industrial and recreational boating, and mechanical aeration result in the creation of aerosols from contaminated water surfaces that are moved to the terrestrial urban environment with onshore winds. The majority of urban centers globally are adjacent to bodies of water that are currently struggling with raw sewage inputs from aging sewer infrastructure, making this both an ecological and public health question. The influence of sewage release into urban waterways includes both human-fecal related organisms (Bacteroides, Faecalibacterium, Blautia, Lachnospiraceae) and organisms associated with urban sewage infrastructure (Trichococcus, Arcobacter, Acinetobacter). To better understand the role of sewage releases and urban sewage infrastructure in determining microbial aerosol content, we used a combination of culture-based and culture-independent microbiological approaches to sample air and water microbial communities in contaminated urban waterways and adjacent public spaces.
We found that microbial aerosols above urban waterways were diverse, and wind direction and wind speed played an important role in determining microbial aerosol concentration and identity. Wind direction in particular modulated the importance of sewage-associated bacteria. Bacterial aerosols detected using culture-based approaches were also evident in culture-independent (454 pyrosequencing) libraries, but culture-independent methods yielded much more diverse bacterial libraries. 454 pyrosequencing libraries revealed a large number of sewage-associated bacteria present in both aerosols and water (e.g. Acinetobacter, Arcobacter, Trichococcus, Faecalibacterium, Blautia, and Lachnospiraceae), including potentially pathogenic bacterial genera. For example, when wind was blowing over aeration ponds at an area waste treatment plant, bacterial aerosols were more similar to samples taken at a nearby flowing Combined Sewer Overflow than they were to other aerosol samples. Similarities between water and aerosol bacterial assemblages suggest an important aquatic influence on air quality in the urban environment.