Turbulence barrier effect during heavy haze pollution events

Abstract Under low wind speed conditions, the frequent intermittent turbulence phenomenon in the atmospheric boundary layer (ABL) greatly weakens the turbulent diffusion of pollutants to cause the heavy haze events. Turbulence may disappear at certain heights forming a laminar flow as if there is a barrier layer hindering the transmission up and down during the heavy haze periods. The turbulent data at five layers and PM2.5 (fine particular matter with a diameter smaller than 2.5 μm) concentration at two levels were used to discuss the barrier that is called the barrier effect vividly. The results revealed that the changes in the PM2.5 concentration at different heights corresponded excellently with the change in vertical turbulence barrier effect. This work explains the physical mechanism responsible for the accumulation of pollutants in heavy pollution events and the influence of turbulent diffusion conditions on the distribution of the PM2.5 concentration.