Microbial Activity in Bioaerosols in Winter at the Coastal Region of Qingdao

Abstract

In order to study the level and size distribution of microbial activity of atmospheric bioaerosols, bioaerosol samples were collected from November 2015 to January 2016 using size-fractionated bioaerosol samplers at the coastal region of Qingdao, and the microbial activity was measured using the fluorescein diacetate (FDA) hydrolysis method. The results showed that the level of microbial activity was in the range of 21.89-108.59 ng·m-3 sodium fluorescein during the sampling period, with an average of 59.43 ng·m-3 sodium fluorescein in Qingdao. Size distribution of microbial activity exhibited a tendency, the activity increased with increasing particle size. The microbial activity on particles with coarse size (>2.1 μm) was higher than that on fine size, with the highest average proportion of 24.06% for coarse size larger than 7.0 μm. The daily variation of microbial activity was different for different samples, which showed no significant diurnal variation in winter. The correlation analysis showed that microbial activity was significantly correlated with wind velocity(r=0.445, n=33, **P<0.01) during the sampling period. However, microbial activity showed no significant correlation with the meteorological factors, such as temperature,relative humidity and UV intensity during the sampling period. Moreover, there was no significant correlation of microbial activity with air quality factors, such as AQI, PM2.5, PM10, CO, NO2, O3 and SO2. Source of air mass had significant impact on microbial activity. The average level of microbial activity was 100.33 ng·m-3 sodium fluorescein on sunny days, and the level decreased to 56.53 ng·m-3 sodium fluorescein on hazy days. When the haze was mixed with fog and this special circumstance lasted for several days, the microbial activity reduced to 37.7% of the level of sunny days. Therefore, consecutive hazy weather had great influence on microbial activity.