Seasonal Variation of Fungal Spores in Size-fractionated Ambient Particulate Matter in Beijing, China, Based on Molecular Tracer Measurements

Abstract:

Fungal aerosols were found to be the dominant fraction of biological aerosol components in the coarse mode in the atmosphere, influencing human health, the biosphere, atmospheric chemistry and climate. However, the total abundance of fungal spores in the atmosphere is rather uncertain and likely underestimated to a large extent by traditional Colony Forming Units (CFU) assays. Flow cytometry (FCM) was utilized in combination with fluorescent stains for the rapid counting of ambient fungal spores in this study. And, the sugar alcohols, mannitol and arabitol, proposed as molecular tracers for fungal aerosol were measured in PM_2.5 and PM₁₀ at an urban site in Beijing, China. The annual average concentrations of arabitol in PM_2.5 and PM₁₀ at the urban site were 7.4±9.4 ng m^-3 and 21.0±20.4 ng m^-3, and the respective mannitol concentrations were 10.3±9.5 ng m^-3 and 31.9±26.9 ng m^-3. Compared to PM_2.5, the seasonal average concentrations of arabitol and mannitol in PM₁₀ were varied more significantly. During summer and autumn higher arabitol and mannitol levels than during spring and winter were observed in coarse particles. Statistics analysis was further grouped into typical dry season (December 2010 to March 2011) and typical wet season (July 2011 to September 2011), revealed the different variation of fungal spores in different seasons. Moreover, the FCM results had significant positive correlation with the concentrations of the fungal tracers (R² was 0.75 and 0.70 for arabitol and mannitol, respectively), supporting the utility of these sugar alcohols as effective fungal tracers.