The temporal and spatial distribution and surface morphology of atmospheric microplastics around the Bohai Sea

Microplastic pollution has become a key environmental issue. At present, research on microplastic pollution in the atmospheric environment has been carried out only in limited regions. Here, the long-term variation in atmospheric microplastic pollution in different coastal cities around the Bohai Sea was compared by selecting three coastal cities(Yantai, Tianjin and Dalian) as case studies. Atmospheric deposition samples were collected from June 2018 to May 2019. The particle size, color, micro-morphology and components of atmospheric microplastics were characterized by stereomicroscopy, scanning electron microscopy and μ-Fourier transform infrared spectrometry, and the atmospheric deposition flux of microplastics was also calculated. Four types of microplastics comprising fibers, films, fragments and granules were found in the atmospheric deposition samples at the three sampling sites and were dominated by fibers(>90%). The colors of microplastics were mainly transparent, blue, red, and black. Most microplastics were < 1 mm in size and the main components of the identified microplastics were cellophane(>50%) and polyester terephthalate(>30%). All the atmospheric microplastics showed definite surface weathering characteristics. The annual atmospheric deposition flux of microplastics at Yantai, Tianjin and Dalian were 2.7×10~4, 8.9×10~4 and 7.2×10~4 particles per square meter, respectively. The results may provide a scientific basis for investigation of atmospheric microplastic pollution and control in the coastal cities around the Bohai Sea.