Characteristics Of Community Composition And Concentration Distribution Of Airborne Microorganisms In Hangzhou

Airborne microbial pollution is one of the main causes of epidemic outbreaks, and it is often more difficult to be prevented and controlled than the chemical pollution at the atmosphere. The outbreak of SARS in2003and swine influenza H1N1in2009makes us realize the importance and urgency to make a systematic and scientific research on urban airbome microbial characteristics. In the present study, four typical sampling sites (Yan’an Road Business Street-YRBS, Tianmushan Jiaogong Cross Road-TJCR, Zhejiang Gongshang University Jiaogong Campus-ZJGSUJC, Breeze-ruffled Lotus at Quyuan Garden-BLQG) were selected for the detail investigation on airborne microbial pollution in Hangzhou. Firstly, the community composition, concentration variation, and size distribution of airborne bacteria and fungi was carried out in Hangzhou with Andersen sampler. Secondly, carbon metabolism characteristics of airborne microbes was conducted in Hanghou with the sampler of Bertin*Coriolis μ. The main results are showed as following:(1) Significant difference in bacterial and fungal concentration was observed in the airin Hangzhou, and the fungal and bacterial concentration was848CFU·m-3and292CFU·m-3, respectively. The concentration of airborne bacteria accounted for29.1%of total microbes in the air, and fungal concentration contributed to70.9%. Small difference in the concentration of airborne bacteria and fungi was detected in the sampling site of YRBS, while big difference was observed in BLQG. Significantly highest microbial concentration was found in ZJGSUJC, followed by the samling sites of YRBS and BLQG, lowest in TJCR. As for the seasonal variation patteren, higher microbial concentration was observed in summer or autumn, followed by spring, and lowest in winter. In a day, the microbial concentration in the air was significantly higher at13:00than at17:00.(2) A total of789airborne bacterial isolates from Hangzhou with different sampling sites and different seasons were identified and distributed across55genera and184species of bacteria. Results showed that the dominant bacteria species were Micrococcus luteus (9.5%), Kocuria roseus (6.8%), Bacillus megaterium (4.6%), Micrococcus roseus (3.4%), and Staphylococcus cohnii (2.5%), and total account for more than40%. Micrococcus (16.5%), Bacillus (14.0%), Staphylococcus (11.3%), Kocuria (11.3%), and Pseudomonas (4.9%), totally accounting for about58%, were determined as the most common culturable airborne bacteria. Moreover, different variation pattern of bacterial composition in the air was determined at different sampling sites and at different sampling seasons in Hangzhou. Data analysis revealed that significantly higher bacterial concentrations were detected at YRBS, followed by TJCR and ZJGSUJC, lowest at BLQG. Additionally, different seasonal variation pattern of bacterial concentration was observed at different sampling sites, and highest bacterial concentration was found in autumn, followed by spring, and lowest in winter at YRBS and ZJGSUJC, while no significant difference of bacterial concentration was found among seasons in a year at the sampling site of BLQG. At the sampling sites of TJCR and ZJGSUJC, bacteria concentration was higher at9:00and17:00that at13:00. As for the size distribution, highest pecent of aborne bacteria was observed at stage1of the sampler at different samplings.(3) The fungal concentration showed significant spatial variation pattern in Hangzhou, and highest fungal concentration was found in ZJGSUJC (1176CFU·m-3), followed by (939CFU·m-3) and YRBS (719CFU·m-3), lowest in TJCR (557 CFU·m-3). At the four selected samping sites, lowest fungal concentration was detected in winter, while highest in summer or autumn. In a day, the fungal concentration in the air was significantly higher at13:00than at17:00. Moreover, airborne fungi were concentrated in stage3, stage4, stage5of the sampler, which was inconsistent with the size distribution of airborne bacteria. In diurnal variation, the fungal percent located in stage3at9:00was higher than13:00and17:00at all the four sampling sites. Highert median diameter of airborne fungi was found at YRBS, followed by TJCR and ZJGSUJC, lowest at BLQG. The median diameter reached higher value at13:00and lower value at17:00.(4) The average well color development (AWCD) values were at stationary phase after240h cultivation in four selected sampling sites. Significant differences in sole carbon utilization characterized as AWCD value were found among four sampling sites, and highest carbon utilization capacity was observed at YRBS, followed by TJCR and ZJGSUJC, and lowest at BLQG. The species abundance and diversity of airborne microbes deceased in the following order YRBS, TJCR, ZJGSUJC, and BLQG. In addition, sugar and amino acid utilization capacity of airborne microbes was significant higher that other carbons sources in four sampling sites. Significant differences in different sole carbon utilization of airborne microbes in the same sampling site were found. The sugar utilization capacity was highest, and polymer utilization capacity was lowest at YRBS. At BLQG, highest sugar utilization capacity was detected, and lowest in amine. Principal component analysis showed that the contribution of PCI and PC2was43.8%and23.4%, respectively, in different sampling sites. Significant differences in carbon metabolic characteristics of microbial community in the air were found among YRBS, BLOG and TJCR, and no differences were observed between TJCR and ZJGSUJC.