Modeling Pollutant Transport and Diffusion in the Atmospheric Boundary Layer Considering Terrain Orography and Meteorological Factors

The problem of modeling the transport and diffusion of pollutants and fine aerosol particles in the atmospheric boundary layer is examined in this article. It takes into consideration the orographic features of the earth’s surface, the velocity of air masses, air temperature, humidity and density, particle diameter, diffusion and absorption coefficients, the interaction of pollutants with the underlying earth’s surface, and other external factors. Computational experiments were conducted using the proposed mathematical framework. These investigations showed that high wind speeds, when coupled with unstable atmospheric stratification and strong pollution transport, significantly raise the concentration of dangerous compounds in the surface layer of the atmosphere. It was established that horizontal flows play a primary role in the dispersion of harmful substances in the atmosphere. Test problems were solved for various particle sizes (dp = 10−7 m; dp = 10−8 m; dp = 10−9 m). It was found that, over time, as the particle size decreases, the area of their propagation significantly expands in the direction of air mass movement. Computational experiments have shown that at wind speeds of u = 2 m/s, v = 0 m/s, w = 0.05 m/s and air temperatures in the range T = 20–30 ∘C, pollutants spread predominantly in the horizontal direction. At low wind speeds, pollutants accumulate near the source. However, with an increase in wind speed to u = 4 m/s, v = 4.5 m/s, w = 0.05 m/s, pollutants are removed from the source at an accelerated rate. At a vertical wind speed of w = 4.5 m/s, particles rise into the upper atmosphere, which contributes to a decrease in their concentration near the earth’s surface over time. Numerical experiments were conducted at various values of relative atmospheric humidity. It was found that at a relative air humidity of 80 %, the particle settling velocity increases by a factor of 1.442; at 90 %, by a factor of 1.765; and at 95 %, by a factor of 2.190.