Contribution of fungal spores to organic carbon in ambient aerosols in Beijing, China

Fungal spores are ubiquitous components of atmospheric aerosols and contributors to the organic carbon (OC) component in ambient aerosols. In order to better understand the role of fungal spores and their impact on atmospheric processes, this study was conducted to investigate the contribution of fungal spores to OC at urban and rural sites in Beijing, China. Ambient concentrations of a molecular tracer for fungal spores, i.e., mannitol in PM10 and PM2.5 samples were measured at an urban site (Tsinghua University, THU) during an entire year, while the observations in PM10 at a rural site (Miyun, MY) were conducted during late spring and summer. Combined with the factor representing the average content of mannitol per spore (0.49 ± 0.20 pg) obtained at the same urban site in Beijing, the year-round number concentrations of fungal spores were obtained. Using a conversion factor of 13 pg C spore−1, the annual average concentrations of spore-OC in PM2.5 and PM10 at the THU site were observed at 0.3 ± 0.2 μgC m−3 and 0.8 ± 0.7 μgC m−3, while the respective contributions of spore-OC to total OC were 1.2 ± 0.7% and 3.5 ± 3.7%, respectively. The contributions of fungal spores to OC in the two size fractions had the following seasonal trend (from highest to the lowest levels): summer, autumn, winter and spring. During the summer sampling season, the contribution of fungal spores to OC was observed at a higher level at the rural site (14.1 ± 10.5%), compared to the urban site (7.3 ± 3.3%). It can be concluded that fungi are a non-negligible source of carbonaceous aerosol even at urban locations such as Beijing, China. Thus, more studies are needed to better understand the spatial, temporal and size distributions of fungal OC contributions to atmospheric aerosols in populated areas.