Bioaerosol investigation: new experimental activity in ChAMBRe, an atmospheric simulation chamber

ChAMBRe (Chamber for Aerosol Modelling and Bio-aerosol Research, www.labfisa.ge.infn.it) is an atmospheric simulation chamber installed in Genoa (IT) and managed by the National Institute of Nuclear Physics and the Physics Department of the University. ChAMBRe is one of the nodes of the EUROCHAMP2020 network of atmospheric simulation chambers. So far, atmospheric simulation chamber have been widely used to study chemical and photochemical processes that occur in the atmosphere. However, following the tracks of a pilot experiment [1], ChAMBRe is the first chamber designed specifically for bio-aerosol studies. The chamber is made in stainless steel with a vertical cylindrical volume of about 2.2 m3 which can be evacuated down to a residual pressure of about 2 10-2 mbar in about 10 minutes. The chamber is equipped with on-line monitors of the internal temperature, pressure and relative humidity. The latter can be controlled by a dedicated humidifier. The air inlet is through an absolute HEPA filter and other gas traps. UV lamps are installed both for ozone production and for sterilization purposes; a variable speed fan is placed in the bottom to favor the mixing of the internal atmosphere. Aerosol concentration and size distribution are monitored in the 5 nm - 18 m range by both a Scanning Mobility Particle Spectrometer and an Optical Particle Counter. Wall reactivity and aerosol life time have been measured by dedicated experiments [2]. At ChAMBRe, the research on bio-aerosol is presently aiming to assess the environmental stress condition and alterations of bacteria viability when they are dispersed in the atmosphere. Basically, the microorganisms behavior is firstly studied in a clean atmosphere and later at the presence of different levels and mixing of anthropogenic pollutants, like NOx, CO, CO2 and Particulate Matter. According to their dimension, bacteria lifetime in ChAMBRe is sufficiently long (typically, 2 -8 hours) to allow this kind of studies. The experimental protocol consists in several consecutive steps: in vitro bacteria growth, injection into ChAMBRe by a Blaustein Atomizer, collection and/or sampling, laboratory analyses. By an automated shelf, several Petri dishes can be placed inside ChAMBRe for singly variable times to collect on a culture medium the suspended bacteria. So far, the ratio between collected and injected CFU turned out to be well reproducible in a set of preliminary but systematics tests and the whole procedure to grow, inject and extract bacteria in ChAMBRE has been put on a firm ground. During the experiment, samples can be also collected by impingers, impactors and filters. Counting of colony forming units (CFU), flow cytometry and scanning electron microscopy, are some of the off-line analyses routinely performed. Up to now, experiments were carried out on Bacillus subtilis and Escherichia coli, belonging respectively to the group of Gram-positive and Gram-negative, with the purpose to extend the analysis to other microorganisms. Results on both the bacterial strains together with a full description of the facility will be presented. This project/work has received funding from the European Union’s Horizon 2020 research and innovation program through the EUROCHAMP-2020 Infrastructure Activity under grant agreement No 730997. [1] P. Brotto et al, Aerobiologia, 2015, doi: 10.1007/s10453-015-9378-2 [2] D. Massabò et al., Atmospheric Environment, submitted