Characterization of microplastics in the atmosphere of megacity Tehran (Iran)

In this study, the characteristics of ambient airborne microplastics were investigated in Tehran to obtain insights into their origins. For this purpose, sampling operations took place at locations with different backgrounds in summer and autumn by using TSP and PM10 high-volume samplers. As a result of microscopic analysis and Raman spectroscopy, the color, shape, number, size, and type of microplastic particles were investigated. Seven types of chemical structures were identified in the particles, among which polypropylene (18.7%) in summer and polystyrene (20%) in autumn had the dominant share. The average number of particles collected using the TSP and PM10 samplers were 1165 +/- 147.64 and 1006.5 +/- 147.64, respectively. The size of microplastic particles in different stations varied between 4 and 3094 mu m. In the seasonal examination of the identified colors, black (38-43%), red (17-19%), gold (13-14%), brown (12% in both seasons), blue (7-10%), yellow (3- 5%), and green (2-5%) had the largest proportions, respectively. The examined microplastics were in three forms: fiber, bead, and fragment, among which the predominant form was fiber, and the most infrequent particles were fragments. Statistical comparisons showed that the sampling location does not have a significant effect on the number and size of particles (p value > 0.05). The season was not identified as a determining parameter for particle size (p value > 0.05). On the other hand, seasonal changes can have a tremendous effect on the microplastic particle number (p value < 0.05). Lastly, to obtain more detailed information about the origin of these particles, continuous and long-term monitoring near known industries and suspected sources of plastic materials and source apportionment studies were suggested.

Automated summary

This study investigated the characteristics and origins of ambient airborne microplastics in Tehran. Different backgrounds and seasons were sampled using TSP and PM10 high-volume samplers. The microscopic analysis and Raman spectroscopy revealed seven types of chemical structures in the particles, with polypropylene in summer and polystyrene in autumn being the most dominant. The color distribution of the particles varied with black and red being the most prevalent. The study also found that season had a significant effect on the number of microplastic particles, while sampling location did not have a significant impact on particle size and number.