Cell concentration, viability and culture composition of airborne bacteria during a dust event in Beijing.

Airborne bacteria were measured when a dust storm passed Beijing in spring 2012 with a focus on cell concentration, viability and TSA- and R2A-cultured strain composition. The concentration varied at an order of 107cells/m3 with dust loading (demonstrated with PM10) and they had a very close correlation (RT2=0.91, p<0.01). At the time of highest PM10 of 652µg/m3, the bacterial concentration reached 1.4×108cells/m3, which was larger than that before and after the dust event by one order. Bacterial viability, the ratio of number concentration of viable cells to total cells, was 32%-64% and smaller in the dust plume than that before the dust arrival. Bacterial strains from the culture ranged between 2.5×104 and 4.6×105CFU/m3 and no correlation with PM10 was determined. Their composition was different before and after the dust arrival according to 16S rRNA gene sequences and strains belong to Actinomycetes and Firmicutes were the majority in the dust samples.