Industrial Dry Heat Island and Dispersion of Air Pollutants Induced by Large Coal-Fired Activities.

Notable anthropogenic heat sources such as coal-fired plants can alter the atmospheric boundary layer structure and the pollutant dispersion, thereby affecting the local environment and microclimate. Herein, in situ measurements inside a coal-fired steel plant were performed by multiple advanced lidars from 21 May to 21 June of 2021 in Yuncheng, Shanxi Province, China. Comparing with an adjacent meteorological site, we found a prominent nighttime dry heat island overhead of the factory, which was 3-10 °C hotter and 30%-60% drier than the surrounding fields. Large-eddy simulations constrained by the measured thermal contrast suggested that the heat-island-induced circulation could upward transport factory-discharged pollutants and horizontally spread them below the residual layer top, forming a mushroom-shaped cloud. The shape, size, and pollutant loading of the cloud were highly determined by thermodynamic variables such as aerodynamic wind and anthropogenic heat flux. Furthermore, these retained residual-layer pollutants can be convected downward to the ground after sunrise through the fumigation effect, causing the peaking phenomena aboveground. These peaks were statistically evidenced to be common in major urban agglomerations in China. The study provides a new insight regarding the origins of residual-layer pollutants and highlights the needs for programming representations of coal-fired heat emissions in mesoscale air-quality models.