Concentration of bacterial aerosols in response to synoptic weather and land‐sea breeze at a seaside site downwind of the Asian continent

Abstract

Airborne bacteria are a major group of bioaerosols, but their temporal and spatial variations in the atmosphere are poorly understood due to a lack of accurate information at an appropriate temporal resolution. In this study, we quantified the concentration and viability of airborne bacteria at a seaside site on the southwestern coast of Japan in spring to investigate their association with synoptic weather, which was governed alternately by cyclones and anticyclones moving in the middle‐latitude westerly flow. The concentration of bacteria, on the order of 105–106 cells m−3, showed a small amplitude of variation, while the viability significantly differed in the range of 23–96% under different weather conditions. Cyclones transported bacteria from the Asian continent in their postfrontal air. Compared to bacteria under other weather conditions, the bacteria in postfrontal air had a large concentration, a low viability, and a close correlation with coarse aerosol particles. In contrast, bacterial concentration and viability in prefrontal air varied over small ranges, and no correlation between bacteria and aerosol particle number concentration was observed. During anticyclones, although bacterial concentration was similar to that in prefrontal air, bacterial viability was high, and the concentration had pulse increases of approximately 2 times the usual level when the wind changed to land/sea breezes. The increases were attributed to the accumulation of bacteria in stagnant air due to local sources. These results show the following two distinct patterns of bacterial concentration and viability at the seaside location of this study: (1) during postfrontal long‐distance dust plume transport related to a cyclone approaching from the Asian continent, the bacterial concentration is correlated with the coarse aerosol particle number concentration and the bacterial viability is low, and (2) pulse increases of viable bacteria are observed at anticyclone conditions corresponding to local sources and land‐sea breeze conditions.

Concentration and Viability of Airborne Bacteria Over the Kuroshio Extension Region in the Northwestern Pacific Ocean: Data From Three Cruises

“…In general, the concentration of airborne bacteria over diverse marine areas is on the order of 10 4 –10 5 cells m −3 , which is lower by a factor of 10–100 than those (10 5 –10 7 cells m −3 ) at inland and coastal sites (Bowers, McLetchie, et al, ; Bowers, Sullivan, et al, ; Chi & Li, ; Hara & Zhang, ; Murata & Zhang, , ). Previous measurements have also shown that the bacterial concentrations over the sea could be lower by a factor of up to 100–1,000 than those in continental air (Prospero et al, ).…”

“…A large proportion (60–88% on average, up to 100%) of the bacteria in airborne aerosols or included in cloud water and precipitation are viable (with intact cell membranes) or metabolically active (Bauer et al, ; DeLeon‐Rodriguez et al, ; Hill et al, ; Hu, Murata, Toyonaga, et al, ; Murata & Zhang, , ; Stopelli et al, ). Previous studies have found that bacteria in cloud water can actively grow, reproduce, and metabolically degrade organic substances, and the viability or metabolic activities of airborne bacteria interact with atmospheric chemical and physical processes (Ariya & Amyot, ; Deguillaume et al, , and references therein).…”

Concentration and Viability of Bacterial Aerosols Associated with Weather in Asian Continental Outflow: Current Understanding

“…Dust arrival always coincided with elevated levels of viable and non-viable bacteria, in which the increase of non-viable bacteria was more remarkable than that of viable bacteria. In later observations at the same areas, it was found that locally-originating bacteria were predominated by viable bacteria (Murata and Zhang 2016). Therefore, the remarkable increase of non-viable bacterial cells during dust events was definitely caused by bacteria brought by dust, although the amounts of bacteria adhering to dust particles and freely-floating bacteria in dust plumes have not yet been accurately quantified.…”

“…Data were from Zhang (2014, 2016) overturn of surface temperature difference between land and sea water in the daytime and the nighttime. The increase is considered to be the consequence of the outbreak of bacterial cells which had accumulated in the nearsurface air from water surface in the early morning and land surface in the late afternoon when the surface air was neutral to stable (Murata and Zhang 2016).…”

Long-range transported bioaerosols captured in snow cover on Mount Tateyama, Japan: Impacts of Asian-dust events on airborne bacterial dynamics relating to ice-nucleation activities

“…In Japan, airborne microbial abundances increase in response to atmospheric depressions, which travel from the Asian continent (Murata and Zhang, 2016).…”