Nanoplastic concentration and potential transport in the Arctic Ocean.

Plastic contamination in the Arctic originates from local anthropogenic activities and long-range transport mediated by oceanic and atmospheric circulation, with nanoplastics representing a major emerging concern. Yet, quantitative data on their environmental distribution remain scarce. Here, we present the first multi-matrix, multi-site, and multi-year assessment of nanoplastics distribution in the Arctic Ocean. We found that polystyrene, polypropylene, and polyethylene nanoplastics are widely distributed across different matrices from the Svalbard region to the central Arctic Ocean. The total concentrations of polystyrene and polypropylene ranging from 10 up to 900 ng L⁻¹. Coastal areas may be more influenced by local human activities, whereas remote regions are likely affected by atmospheric transport and inputs associated with the Transpolar Drift. The extent to which each source contributes remains uncertain and may vary spatially. Differences in distribution across environmental matrices were also observed, with higher concentrations in snow and surface ice than at the ice-sea interface. The sea ice act as a temporary reservoir and secondary source of nanoplastics through redistribution processes across the snow-ice-seawater interface. These findings indicate the necessity for multi-scale, multi-temporal, and multi-spatial investigations, which are crucial for understanding the sources, transport pathways, and environmental fate of nanoplastics within the Arctic ecosystem.