Enhancing urban biosecurity and sustainability through a microclimatic bioaerosol risk management framework

Urban biosecurity is closely linked to national security and social stability. However, urban biosafety issues using bioaerosols as a carrier remain insufficiently understood. This study elucidates the mechanisms of bioaerosol emission and migration within urban environments through an integrated approach combining detailed field measurements, experimental scaling, advanced theoretical algorithms, and high-fidelity numerical simulations. We are mainly focused on the impact of variations in meteorological conditions, release conditions and particle size on the bioaerosol dispersion and infection risks. Results reveal that high temperatures and low winds elevate bioaerosol concentrations, while post-precipitation changes in humidity and wind speed alter deposition patterns. Increasing release height and particle size significantly mitigate infection risk, with microclimatic conditions exerting a more substantial impact than particle size. Furthermore, we propose an optimized evacuation strategy for urban high-risk areas, incorporating human collision dynamics and road network configurations into an enhanced cellular automata model. Under identical evacuation paths, the evacuation time for children is the longest, while adults exhibit the shortest time. As the release height increased from 0 to 80 m, the global evacuation time increased by approximately 2.11 times. Notably, the local evacuation time was notably higher than the global, with the discrepancy increasing non-linearly with the release height. This study offers theoretical insights for improving urban biosecurity preparedness and enhancing emergency response capabilities.