Research on the Spatial Distribution Characteristics and Inhalation Health Risk Assessment of Bacterial Aerosols in Spraying Environments

As a key water source for urban landscape entertainment and miscellaneous municipal uses, the reuse safety of reclaimed water has attracted much attention. Given the deficiencies in the current research on bacterial aerosol-related risks, this study conducted systematic research on the spatial distribution law of bacterial aerosols in spraying environments and the exposure characteristics of various populations through simulated spraying experiments and population surveys, and on this basis, quantitatively evaluated the inhalation risk of bacterial aerosols. Results indicated that the concentration of bacterial aerosols in the spatial position within the water source and their residence time at different positions were related to the bacterial concentration of the sprayed water source. Specifically, the concentration of bacterial aerosols and the atomization factor decreased with the increase in the horizontal distance from the nozzle, and reached a saturated state at the eighth minute after the nozzle started spraying. At a height of 1.5 m, and at distances of 1 m, 2 m, 3 m, and 4 m from the nozzle, the atomization coefficients (mL water/m3 air) were 30.25, 8.52, 0.81, and 1.33 × 10−3, respectively. However, the particle size distribution of bacterial aerosols in space was independent of the bacterial concentration in the water source. The peak particle size of bacterial aerosols was between 2.1 and 4.7 µm, and its concentration accounts for more than 50%. Based on the above results, the exposure characteristics of the instantaneous contact time of the crowd exposed to the spray water of park lawn irrigation and the spray water of sprinklers on roads were obtained through simulated shooting experiments. Results showed that under the same environment, when people were exposed to the spray of park lawn irrigation and the spray of sprinklers on roads, the health risk of a single inhalation was relatively high. The single health risk of the crowd manifested as follows: adult males > adult females > children; however, none of them exceed the acceptable risk level of 10−3. The research findings of this paper can provide a scientific basis for the safe reuse of reclaimed water