[Characteristics of Microplastic Present in Urban Road Dust]

Microplastics (MPs), as an emerging contaminant, have attracted wide attention due to their potentially negative impact on the ecosystem. However, information on microplastic pollution in terrestrial environments, especially road dust, is still rare. In this study, the microplastic pollution in road dust from the Yushan District of Ma'anshan City was characterized. The abundances of MPs accumulated per square meter of road and dust were (18.11±32.36) n·m^-2 and (223.00±197.01) n·kg^-1, respectively, and the contents were (27.29±72.64) mg·m^-2 and (385.23±628.93) mg·kg^-1, respectively, with polypropylene (PP, 58.90%) and polyethylene (PE, 30.08%) as the major polymers based on the number fraction in dust. Additionally, in a given road area, the abundance of MPs in commercial areas was the highest[(78.32±101.24) n·m^-2], followed by residential[(19.81±14.30) n·m^-2], industrial[(10.95±5.54) n·m^-2], suburban[(8.56±8.13) n·m^-2], and educational[(6.99±5.74) n·m^-2] areas. In the case of the same area, the microplastic pollution from the commercial area was heavier. Regarding the shape of the MPs detected in road dust, 66.64% were present as films, 16.14% as granules, 14.13% as fibers, and 3.10% as spheres out of the total number detected. Most of the MPs were less than 1000 μm in size. For a particular road area, the abundance of MPs was significantly correlated with the mass of dust (r=0.599, P<0.01), whereas there was no obvious correlation for the mass of MPs (r=0.067, P=0.780). Generally, the road dust can accumulate continuously prior to cleaning, whereas the mass of the MPs will not increase unless there is external input. Otherwise, MPs on the road will be broken down under the action of external forces such as vehicles, resulting in an increase in the number of MPs.