Airborne bacteria viability and air quality: a protocol to quantitatively investigate the possible correlation by an atmospheric simulation chamber

Abstract. Biological Particulate Matter or bioaerosol are a subset of atmospheric aerosol. They influence climate, air quality and health via several mechanisms which often are poorly understood. In particular, the quantitative study of possible relationship between bioaerosol viability and air quality or meteorological conditions is an open and relevant issue. The difficulty of retrieving such possible correlations by analyses of data collected during in-field campaigns, can benefit of targeted experiments conducted in well controlled conditions inside Atmospheric Simulation Chambers, ASCs. ChAMBRe (Chamber for Aerosol Modelling and Bio-aerosol Research) is an ASC in Genoa (Italy) designed and built to perform experimental research on bioaerosol. In this article we focus on bacteria viability. A multi-step protocol was developed and thoroughly tested: cultivation of a suitable bacteria population, nebulization and injection in the chamber of viable cells, exposure and monitoring of the viability variation inside ChAMBRe, hold at selected conditions, and finally incubation and counting of the concentration of viable bacteria. The whole procedure showed a reproducibility at the 20 % level when ChAMBRe is kept in a reference “baseline” condition. This figure quantifies the protocol sensitivity as well to changes in viability when bacteria are exposed in other (e.g., polluted) conditions. First results showing a viability reduction observed exposing the E. coli strain to NOX concentrations and solar irradiation are presented and discussed. Present results pave the way to systematic studies aimed at the definition of dose-effect relationship for several bacteria strain at atmospheric pollutants.