Abstract
Since 2013, severe haze events frequently have occurred in Beijing between October and March, which have created a significant public health threat. Although variations in the chemical composition of these haze events have been studied widely, information pertaining to airborne bacteria in such haze events remains limited. In this study, we characterized the concentration, community structure, and composition of the airborne bacteria in response to nine haze events that occurred between October 1, 2015, and January 5, 2016. We also analyzed the correlations of airborne bacteria (concentration, community structure, and composition) with pollution levels and meteorological factors. The results indicated that airborne bacterial concentration showed a positive cyclical correlation with the haze events, but the bacterial concentration plateaued at the yellow pollution level. In addition, we found particulate matter (PM10) and relative humidity to be key factors that significantly affected the airborne bacterial concentration and community structure. Moreover, Halomonas and Shewanella were enriched on haze days for all nine of the haze events. Finally, the correlations between haze pollution and airborne bacteria in midwinter were weaker than those in fall and early winter, indicating an obvious staged distinction among the effects of haze on airborne bacteria. Our study illuminated the dynamic variation of bioaerosols corresponding to the cyclical haze events and revealed the interactions among air pollution, climate factors (mainly relative humidity), and airborne bacteria. These results imply that different strategies should be applied to deal with the potential threat of airborne bacteria during haze events in different seasons.
Highlights
Since January 2013, severe haze events frequently have occurred in Beijing (Ouyang, 2013), which have posed a serious threat to public health (Guan et al, 2016) and have disturbed the outdoor activities of the local people (Quan et al, 2014)
Bioaerosols were sampled from nine independent haze events (Nos. 1–9) that occurred over different seasons and that presented distinct temperatures and concentrations of SO2 (Supplementary Figure S3)
According to temperature and concentration of SO2, the nine haze events were classified into three stages: Stage I (Nos. 1–3 haze events from October 1 to November 6, 2015) corresponding to the non-heating season; Stage II (Nos. 4–6 from November 25 to December 15, 2015) belonging to the heating season with average temperature above 0◦C; and Stage III (Nos. 7–9 from December 18, 2015, to January 5, 2016) belonging to the heating season, with an average temperature lower than 0◦C
Summary
Since January 2013, severe haze events frequently have occurred in Beijing (Ouyang, 2013), which have posed a serious threat to public health (Guan et al, 2016) and have disturbed the outdoor activities of the local people (Quan et al, 2014). These haze events either from primary source emissions (Wu et al, 2016) or from secondary formation (Huang et al, 2014; Wang et al, 2016). Studies on the relationships between bioaerosols and haze events are necessary to prevent their potential hazards
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