| Summary: | Bioaerosols are microorganisms or functional parts of them or other biological matter suspended in air. Examples are bacteria, viruses, pollen, spores, or smaller plant debris. In the atmosphere, bioaerosols can play various functional roles, such as facilitating the spread of genetic material. Moreover, they can play an important role in climate by serving as ice nucleating particles and thus participating in cloud formation. Bioaerosols might play a significant role in a changing Arctic, where aerosol concentrations can be very low, and where natural as well as anthropogenic aerosol sources are subject to drastic changes due to climate change. In the Arctic, aerosols and clouds are prominent actors in climate by mediating short- and long-wave radiation interactions, which are further complicated by the presence of high-albedo surfaces such as sea ice. Thus, constraining the sources of aerosols and their interaction with clouds is key to understanding the Arctic climate and the changes it has been and will undergo. In this work, we used a single-particle instrument to differentiate bioaerosols from other particles on the basis of their fluorescence and light-scattering signal. In the Baltic Sea, we found that bioaerosols are at least 1 in every 104 coarse particles emitted by sea spray. Their temporal emission pattern was not directly correlated with biological tracers, such as chlorophyll; instead, their emission was modulated by the transition between different water masses. The same technique was then applied to a one-year measurement campaign at an Arctic mountain top observatory as part of a greater aerosol-cloud interaction campaign. The recorded seasonal cycle of bioaerosol concentrations peaked in summer and was most likely related to regional terrestrial sources, as its appearance coincided with a decrease in snow cover and an increase in vegetation activity. Moreover, bioaerosols were found to drive the concentration of high-temperature ice nucleating particles, even in winter. In the third study, the ...
|
|---|