High nanoplastic concentrations across the North Atlantic

<title>Abstract</title> Plastic pollution of the marine realm is globally ubiquitous and a substantial body of research has concentrated on microplastics (1 µm – 5 mm). Ocean nanoplastics (&lt;1 µm), in contrast, are understudied and the mass budget of this domain thus remains unknown. Here we measured nanoplastic concentrations on an ocean basin scale along a transect crossing the North Atlantic from the subtropical gyre to the northern European shelf using Thermal Desorption – Proton Transfer Reaction – Mass Spectrometry. Substantial amounts of polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) nanoplastic (~2-25 ng ml^-1) were observed throughout the entire water column (measured in the well-mixed surface layer, at 1 kilometer depth and in bottom waters). We found higher nanoplastic concentrations in the well-mixed surface layer closer to the European continent, while bottom waters contained the lowest nanoplastic concentrations (primarily comprising PET). A conservative extrapolation of our findings shows that the total (PS+PVC+PET) nanoplastic mass in the well-mixed surface layer of the North Atlantic Ocean alone amounts to 33-50 million tonnes (Mt). This is in the same range or exceeds previous macro/microplastic budgets estimates for the entire Atlantic¹ or global Ocean^2,3,4. Our findings suggest that nanoplastics are the most important part of ocean plastic pollution.