Long-range transport of atmospheric microplastics deposited onto glacier in southeast Tibetan Plateau

Micoroplastics (MPs) can be transported through atmospheric circulations, and have caused global attentions due to their potential risk to the environment. In this study, MPs in snowpit samples collected from Demula (DML) glacier in southeast Tibetan Plateau were investigated. The results showed that the average abundance of MPs in snow was 9.55 +/- 0.9 items L-1, with dominant shapes of plastic fibers and films. MPs size was dominated by MPs < 200 mu m, with detected minimum size of 48 mu m from the DML glacier. MPs in snowpit indicated seasonal variations, showing relatively higher abundance during the monsoon season than that during the non-monsoon season. The chemical composition of MPs and backward air mass trajectory modeling revealed that MPs in DML snowpit mostly originated from the atmospheric long-range transport, suggesting the glacier in southeast Tibetan Plateau can be a temporal sink of atmospheric MPs. The surface structure of the MPs was rough and adhered to a large amount of mineral dust and metallic particles, revealed that these MPs have undergone severe weathering during transportation and after deposition. Based on the MPs data, multi-year average precipitation, and glacier mass balance of DML glacier, the deposition flux of MPs on DML glacier was estimated to be about 7640 +/- 720 to 9550 +/- 900 items m(- 2) yr(-1) and the export from melting water was about 5.9 +/-;1.3 x 109 to 6.6 +/- 1.4 x 109 items yr(-1), indicating the glacier may be also an important source of MPs to the downstream ecosystems. These results provided the current status of MPs pollution on the Tibetan Plateau glaciers and new data to the study of MPs in typical cryospheric regions.

Automated summary

This study investigated microplastic pollution in snowpit samples collected from the Demula glacier in the southeast Tibetan Plateau. The results showed that microplastics, mainly in the form of plastic fibers and films, were present in the snow, with a size predominantly smaller than 200μm. The abundance of microplastics in the snowpit varied seasonally, with higher levels during the monsoon season. The chemical composition and air mass trajectory modeling indicated that these microplastics primarily originated from long-range atmospheric transport. Moreover, the surface structure of the microplastics suggested severe weathering during transport and deposition. Based on the data, the deposition flux and export from melting water were estimated, indicating that the glacier may also act as a significant source of microplastics to downstream ecosystems.