Concentration and Size Distribution of Culturable Airborne Microorganisms in Outdoor Environments in Beijing, China

A one-year (from June 2003 to May 2004) study of airborne microbial concentration and size distribution was conducted systematically at three selected sampling sites in Beijing. Microbial samples were collected in triplicate for 3 min, 3 times per day, for 3 consecutive days of each month using FA-I sampler (imitated Andersen sampler, made by Applied Technical Institute of Liaoyang, China). Results showed that the concentration of total culturable microorganisms ranged from 4.8 × 10 2 colony forming units (CFU)/m 3 to 2.4 × 10 4 CFU/m 3 , with an arithmetic mean of 3.7 × 10 3 ± 2.1 × 10 2 (standard deviation) CFU/m 3 . As a whole, the percentage of airborne bacteria, accounting for 59.0% of the total culturable microorganisms, was significantly higher than those of airborne fungi (35.2%) and actinomycetes (5.8%). At RCEES (Research Center for Eco-Environmental Sciences—a culture and education area) and XZM (Xizhimen—a main traffic line), significantly higher percentages of airborne bacteria were found as ...