Quantitative distribution of human exhaled particles in a ventilation room.

Respiratory viruses can be attached to human exhaled particles and spread from person to person through respiratory activities. The purpose of this study is to obtain the quantitative description formula of human exhaled particles in the ventilated room through amount number of numerical simulation calculations and regression statistical analysis of the simulated data. In this study, a combination of numerical simulation and laboratory experiments was used, and the results were tallied preferably. Bacillus subtilis was released as a release source to investigate the migration and distribution of bioaerosol. The results show that under the condition of high air supply velocity, due to the disturbance of human respiration and airflow, the diffusion velocity of exhaled particles was faster and the diffusion range is larger than that of low air supply velocity within the same time frame. No matter where the location of the manikin was in the room, the exhaled particles would spread to the whole room in at least 900 s. The method used in this study could be used to predict the distribution of human exhaled particles concentration in different indoor spaces, such as public transport and hospitals. These findings could provide valuable reference for the location of indoor air purifiers, which plays a guiding role in the construction of a healthy indoor environment.

Seasonal dynamics of airborne culturable fungi and its year-round diversity monitoring in Dahuting Han Dynasty Tomb of China.

Dahuting Han Dynasty Tomb, famous for its magnificent and realistic murals in China, was selected for a year-long study as the research target in relation to microbiological degradation of cultural heritage. This dissertation has investigated the predominant genera of the airborne fungal microbial community in Dahuting and analyzed the seasonal distribution characteristics and temporal-spatial particle size distribution of the fungi in a tomb environment. The combination of culture-dependent and high-throughput sequencing methods was utilized for counting the collected fungi and identifying the strains. Results showed that seasonal dynamics significantly affect the fungal concentration, with higher-level concentrations observed in spring and autumn. However, seasonal variation has little effect on the fungal particle size distribution characteristic trend, and the higher concentration invariably appeared in stage IV to VI (0.65-3.3 µm) of the Andersen six-stage sieve impactor. The ITS (Internal Transcribed Spacer) rRNA gene-based sequences disclosed a high airborne culturable fungal abundance, dominated by Talaromyces spp. (20%-38.4%), followed by Aureobasidium spp. (19.4%-25.6%), Penicillium spp. (10.8%-23.9%) and Aspergillus spp. (8.2%-23.1%). Our research provides valuable information for reasonable protection measures and scientific prevention work of the murals in Dahuting Han Dynasty Tomb.