Investigation of Diameter and Aerodynamic Weight Distribution and Atmospheric Particle Shapes Within the Traffic Plan Area of Tehran

Implementing control plans, monitoring, and formulating traffic and management laws requires obtaining basic information about the origin of particles, physicochemical properties, and their behavior in the atmosphere. Gathering this information requires studying the various dimensions of the nature of particles, most of which will not be directly possible. The challenge of air pollution in the metropolis of Tehran requires fundamental studies, and in this study, we tried to present new dimensions of physicochemical and fundamental properties of atmospheric particles in Tehran. 

The particle collection process to evaluate their concentration and chemical composition was performed by a high-volume sampler for 1 to 24 hours and an average flow of 1.7 m3/min on fiberglass filters. Also, to determine the aerodynamic diameter distribution of the particles, a cascade sampler (Anderson impactor) with a flow of 28.3.3 L/min was used for 72 hours to 7 days. After sampling, the samples were prepared to determine the total concentration and aerodynamic distribution in the laboratory. 

The results showed that the mean particle concentration during the sampling period was 118.6 ± 11.9 µg/m3. During the sampling period, the highest concentration of collected particles was 154.61 ± 22.1 and the lowest was 129/12 ± 23.15 µg/m3. The results of SEM analysis of the collected samples showed that the particles were present in a spherical, irregular, fibrous shape as well as crystalline shape. The predominant elements in these samples are K, Ca, Cl and Fe, which are found in combination with Ti, Zn. Cluster-like and amorphous structures rich in O, Zn, Mg, Fe, K, Si, and Na were observed in particles with dimensions of 2 to 7 micrometers. 

According to the results and comparison with other work done in this field, more particulate matter is emitted during fuel combustion processes by industry and urban transportation. Larger particles are also produced and emitted by vehicles, construction, and industry during human activities such as road dust.