Characterizing atmospheric biological aerosols at a suburban site in Guangzhou, southern China by airborne microbes, proteins and saccharides

Bioaerosols in ambient environment can be evaluated using various techniques. However, the results of bioaerosols obtained using different methods are rarely compared. The relationships between different bioaerosol indicators and their behaviors under the influence of environment factors are seldom investigated. Here we used airborne micro-bial numbers, proteins and saccharides concentrations as the indicators to characterize bioaerosols in two seasons with different source contribution, air pollution situation and meteorological conditions. The observation was conducted at a suburban site in Guangzhou, southern China, during the winter and spring periods of 2021. Airborne microbes were observed with an average of (1.82 +/- 1.33) x 106 cells/m3, converted to the mass concentration level of 0.42 +/- 0.30 mu g/m3, comparable but lower than that of proteins (0.81 +/- 0.48 mu g/m3). Both of them were much higher than the average concentration of saccharides (19.93 +/- 11.53 ng/m3). During the winter period, significant and good cor-relations were observed between the three components. In spring, a biological outbreak was observed in late March with a strong elevation of airborne microbes followed by elevations of proteins and saccharides. The retardation of pro-teins and saccharides could be the result of the enhanced release from microorganisms under the influence of atmo-spheric oxidation processes. Saccharides in PM2. 5 were studied to reveal the contribution of specific sources of bioaerosols (e.g. fungi, pollen, plants and soil). Our results show that primary emissions and secondary processes should play their roles in the variations of these biological components. By comparing the results of the three methods, this study provides an insight into the applicability and variability of bioaerosol characterization in the ambient envi-ronment with respect to various influences of sources, atmospheric processes and environmental conditions.