Atmospheric microplastic over the South China Sea and East Indian Ocean: abundance, distribution and source.

At present, microplastic (MP) is pervasive globally and has a regional difference. Recent studies have identified MP in the terrestrial atmospheric environment. However, the connection between terrigenous atmospheric MP emissions and impacts over the ocean is not well known. Here, we present the distribution of atmospheric MP abundance over the ocean based on a transoceanic survey conducted across 21 sampling transects from the Pearl River Estuary (PRE) to the South China Sea (SCS) and then to the East Indian Ocean (EIO). The abundance of atmospheric MP over the PRE (4.2 ± 2.5 items/100 m3) was significantly higher than that over the EIO (0.4 ± 0.6 items/100 m3). However, the abundance of atmospheric MP in the SCS (0.8 ± 1.3 items/100 m3) was not significantly different from the EIO and PRE. This result revealed that MP undergoes long-range transport, more than 1000 km away, through the atmosphere, but atmospheric MP transmission as the main source of oceanic MP based on transoceanic studies is not a plausible assumption. Furthermore, backward trajectory model analysis of 21 sampling transects preliminary showed the potential sources of atmospheric MP over the PRE, SCS, and EIO.