Assessment of the impact of atmospheric pollutants on bacteria viability by an atmospheric simulation chamber

The aim of the PhD project was to make possible systematic studies of the bio-aerosols behavior in different atmospheric conditions, with the final goal to assess the link between pollution levels and bio-aerosol dispersion and impact. The research has been carried out at ChAMBRe (Chamber for Aerosol Modelling and Bio-aerosol Research), a 2.3 m3 stainless steel atmospheric simulation chamber. Experiments conducted inside confined artificial environments, such as the Atmospheric Simulations Chambers (ASCs), where atmospheric conditions and composition are controlled, can provide valuable information on bio-aerosols viability and their interaction with other atmospheric constituents. The first phase of the PhD project was dedicated to the characterization of the chamber, the related instrumentation and the design and development of the experimental set-up. An experimental protocol for chamber studies on bio-aerosols was developed and thoroughly tested with two bacteria model strains (B. subtilis and E. coli). An intense effort has been dedicated to fully characterize the performance of three different nebulization systems specifically designed for bioaerosol applications to assess their application in experiments at ASCs. A WIBS-NEO provides the size-segregated, real-time monitoring of the total bio-aerosol concentration inside the chamber. With a clean atmosphere maintained inside ChAMBRe, the ratio between injected and extracted viable bacteria turned out to be reproducible at 11 % and 13% level with E. coli and B. subtilis respectively. After assessing this way the reproducibility and sensitivity of the whole experimental procedure, the first tests to explore the possible correlation between bacteria viability and air quality were carried out. The two bacteria models, B. subtilis and E. coli, were subjected to high concentrations of nitrogen oxides and soot particles, two of the most common pollutants emitted by anthropogenic sources.