Human Activity and Environmental Drivers of Airborne Bacterial Dynamics on a University Campus: Insights from Cultivation and Metagenomic Analysis

University campuses function as semi-enclosed microenvironments where human activity and natural factors jointly shape the composition and dynamics of airborne microbial communities. This study investigated the spatial-temporal patterns of airborne bacterial abundance, diversity, and community structure across six functional areas—three indoor (Dormitory Common Areas, Cafeteria, Lecture Halls) and three outdoor (Sports Complex, Courtyard, Study Room) over a six-day period encompassing both holidays and school days. Bacterial abundance ranged from 56 CFU/m³ in the Cafeteria to 183 CFU/m³ in the Dormitory Common Areas. During holidays, the highest average concentration (214 CFU/m³) was recorded in Dormitory Common Areas, while the lowest (57 CFU/m³) was observed in Lecture Halls. On school days, the Sports Complex exhibited the highest average concentration (193 CFU/m³), whereas the Cafeteria remained the lowest (52 CFU/m³). Notably, morning and evening sampling revealed diurnal variation, with the Sports Complex reaching up to 216 CFU/m³ in the afternoon of school days. Correlation analysis indicated a strong negative relationship between bacterial abundance and both temperature (r = − 0.72) and humidity (r = − 0.83) in indoor environments, while wind speed showed a strong positive correlation (r = 0.97) with bacterial abundance in outdoor sites like the Sports Complex. These findings suggest that both ventilation-driven dispersion and resuspension via wind significantly influence bacterial levels. Metagenomic analysis revealed distinct microbial signatures: indoor environments were dominated by human-associated genera such as Staphylococcus , especially during high occupancy, while outdoor sites were enriched with environmental genera like Pseudomonas and Bacillus . Shannon diversity was highest at the Sports Complex during school days and lowest in the Study Hall during holidays, reflecting the impact of both human presence and environmental exposure. Opportunistic pathogens including Acinetobacter baumannii and Streptococcus pneumoniae were detected across multiple sites, raising concerns about airborne exposure in densely populated indoor areas. This study underscores the importance of integrating environmental monitoring and human activity profiling to inform public health strategies on campuses. Recommendations include enhanced ventilation in high-occupancy zones, adaptive disinfection protocols, dust control in open areas, and the use of air purification systems to mitigate bioaerosol-related health risks.