Abstract
The source, characteristics and transport of viable microbial aerosols in urban centers are topics of significant environmental and public health concern. Recent studies have identified adjacent waterways, and especially polluted waterways, as an important source of microbial aerosols to urban air. The size of these aerosols influences how far they travel, their resistance to environmental stress, and their inhalation potential. In this study, we utilize a cascade impactor and aerosol particle monitor to characterize the size distribution of particles and culturable bacterial and fungal aerosols along the waterfront of a New York City embayment. We seek to address the potential contribution of bacterial aerosols from local sources and to determine how their number, size distribution, and taxonomic identity are affected by wind speed and wind direction (onshore vs. offshore). Total culturable microbial counts were higher under offshore winds (average of 778 CFU/m3 ± 67), with bacteria comprising the majority of colonies (58.5%), as compared to onshore winds (580 CFU/m3 ± 110) where fungi were dominant (87.7%). The majority of cultured bacteria and fungi sampled during both offshore winds (88%) and onshore winds (72%) were associated with coarse aerosols (>2.1 µm), indicative of production from local sources. There was a significant correlation (p < 0.05) of wind speed with both total and coarse culturable microbial aerosol concentrations. Taxonomic analysis, based on DNA sequencing, showed that Actinobacteria was the dominant phylum among aerosol isolates. In particular, Streptomyces and Bacillus, both spore forming genera that are often soil-associated, were abundant under both offshore and onshore wind conditions. Comparisons of bacterial communities present in the bioaerosol sequence libraries revealed that particle size played an important role in microbial aerosol taxonomy. Onshore and offshore coarse libraries were found to be most similar. This study demonstrates that the majority of culturable bacterial aerosols along a New York City waterfront were associated with coarse aerosol particles, highlighting the importance of local sources, and that the taxonomy of culturable aerosol bacteria differed by size fraction and wind direction.
Highlights
The atmosphere is widely recognized as a habitat containing numerous and diverse microorganisms (Lighthart, 1997; Pashley et al, 2012; Smets et al, 2016)
In order to address this gap, this study aims to answer several questions pertaining to the local connection between microbial communities in water and air and the characteristics of the bioaerosols present along a New York City waterfront
Despite increased concentrations in the offshore wind conditions, both onshore and offshore winds resulted in similar aerosol particle size distributions (Fig. 3)
Summary
The atmosphere is widely recognized as a habitat containing numerous and diverse microorganisms (Lighthart, 1997; Pashley et al, 2012; Smets et al, 2016). The concentrations of viable microbial aerosols can vary across temporal and spatial scales (Lighthart, 1997). The concentration of viable airborne bacteria may be on the order of hundreds of cells per cubic meter, while in terrestrial environments, concentrations may be an order of magnitude higher (Lighthart, 1997; Shaffer & Lighthart, 1997; Burrows et al, 2009). The flux of bacteria in coastal environments may vary by orders of magnitude (Lighthart, 1997). Bacteria and fungi can be a source of disease and allergens, making their transport through urban environments an area of special concern (Smets et al, 2016). Information about the sources and size distribution of culturable bacteria and fungi aerosols remain as gaps in our understanding of urban microbiology
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