Turbulent Diffusion Effect on PM_2.5 Concentration above an Urban Canopy

Abstract

Turbulent diffusion played a role in mixing the pollutants that caused instability in the atmospheric boundary layer by analyzing the features of turbulent transfer, diffusion coefficients of momentum (km) and heat (kh), and the shape of universal functions of PM2.5. Observation of turbulence measured by 3D ultrasonic anemometer for one week in both January and July 2016, in Baghdad, Iraq. K and PM2.5 concentrations had a strong inverse relationship under three atmospheric stabilities: unstable, neutral, and stable conditions, this indicated that turbulent diffusion’s impact was significant during the observed period. According to the comparisons between Km and Kh, the strength of the turbulent exchange of PM2.5 concentration at stations may be weaker or stronger than the strength of the turbulent momentum and heat exchange. Finally, the result shows the turbulent diffusion coefficient by heat Kh was larger than the turbulent diffusion coefficient by momentum Km.