Atmospheric microplastics in the Northwestern Pacific Ocean: Distribution, source, and deposition

Microplastic pollution is recognized as a ubiquitous global issue. However, limited information is available concerning microplastics in the marine air. Here we present the occurrence and distribution of atmospheric microplastics in the Northwestern Pacific Ocean, with abundance ranging from 0.0046 to 0.064 items/m³. The microplastics were in various shapes and polymer types, of which fibrous rayon (67%) and polyethylene terephthalate (PET, 23%) accounted for the majority. The atmospheric microplastics in the pelagic area showed higher abundance and smaller size compared to those in the nearshore area, indicating smaller-sized microplastics in the atmosphere might travel long distances over the ocean. The atmospheric microplastic distribution was not only affected by weather conditions but might also be related to the microplastic sources. The microplastic polymer types combined with the backward trajectory model analysis showed that atmospheric microplastics in the Northwestern Pacific Ocean mainly originated from the land and the adjacent oceanic atmosphere. Spearman's correlation coefficient of the relationship between the features of microplastics in the atmosphere and surface seawater tended to increase with increasing offshore distances. Our field-based research revealed that atmospheric microplastics were a non-negligible source of marine microplastic pollution.