Variations and the Role of Proteins in Bioaerosols During Air Pollution Processes in Xi’An, China

Proteinaceous matter is an important component of atmospheric bioaerosols, which can cause adverse health effects and also influence the air quality and climate change. However, there is little attention to the variations and the role of aerosol proteinaceous matter during air pollution process. In this study, bioaerosol samples in PM2.5 were collected in Xi'an, China in autumn and winter as well as during three haze pollution events. The total proteins and some other chemical components were analyzed for these aerosol samples. The statistical analysis methods and backward trajectory model were used to determine the response of aerosol protein to air pollution level and their potential sources. The results showed that the total protein concentration in bioaerosols exhibited distinct seasonal variations with higher value in winter (6.86 ± 3.29 μg·m-3) compared to that in autumn (3.70 ± 2.04 μg·m-3). The hourly variation of protein concentration showed slightly higher at night than in the daytime. Further, the concentration of total proteins increased with the deterioration of air quality. Correlation analyses suggested that aerosol protein came mainly from biomass burning, agricultural activities and plant sources, while long-distance air mass transport might have an important contribution to aerosol proteins during haze pollution process. Another important finding was that aerosol proteins might be involved in photochemical oxidation process in the atmosphere. The present results may provide scientific basis for a better understanding of the variations and the role of aerosol proteinaceous matter during the formation and development of haze pollution.