Abstract
Plastic materials are increasingly produced worldwide with a total estimated production of >8300 million tonnes to date, of which 60% was discarded. In the environment, plastics fragment into smaller particles, e.g. microplastics (size < 5 mm), and further weathering leads to the formation of functionally different contaminants – nanoplastics (size <1 μm). Nanoplastics are believed to have entirely different physical (e.g. transport), chemical (e.g. functional groups at the surface) and biological (passing the cell membrane, toxicity) properties compared to the micro- and macroplastics, yet, their measurement in the environmental samples is seldom available. Here, we present measurements of nanoplastics mass concentration and calculated the deposition at the pristine high-altitude Alpine Sonnblick observatory (3106 MASL), during the 1.5 month campaigh in late winter 2017. The average nanoplastics concentration was 46.5 ng/mL of melted surface snow. The main polymer types of nanoplastics observed for this site were polypropylene (PP) and polyethylene terephthalate (PET). We measured significantly higher concentrations in the dry sampling periods for PET (p < 0.002) but not for PP, which indicates that dry deposition may be the preferential pathway for PET leading to a gradual accumulation on the snow surfaces during dry periods. Air transport modelling indicates regional and long-range transport of nanoplastics, originating preferentially from European urban areas. The mean deposition rate was 42 (+32/-25) kg km−2 year−1. Thus more than 2 × 1011 nanoplastics particles are deposited per square meter of surface snow each week of the observed period, even at this remote location, which raises significant toxicological concerns.
Highlights
Plastics pollution has been recognised to be a global problem, as particles of various sizes have been detected in water, soil and air, from urban to remote areas (Allenet al., 2019; Dris et al, 2016; Ivleva et al, 2017; Ter Halleet al., 2017)
We recently developed a chemical method based on Thermal Desorption - Proton Transfer Re action - Mass Spectrometry (TD-PTR-MS), to selectively quantify nano plastics of different types with the highest sensitivity reported to date (Materic et al, 2020)
We note that chemical ionization of thermally desorbed plastics va pours generates neutral molecules (e.g. CO2) that are not seen by the method, the concentrations we report are conservative and represent lower limits (for details see the methods section and our previous publication (Materic et al, 2020))
Summary
Plastics pollution has been recognised to be a global problem, as particles of various sizes have been detected in water, soil and air, from urban to remote areas (Allenet al., 2019; Dris et al, 2016; Ivleva et al, 2017; Ter Halleet al., 2017). It has been shown that microplastics can be transported from air to sea, and very recently, a study showed emission from the sea surface back to air (Allenet al., 2020; Liuet al., 2019). These studies suggest that different environmental systems (sea, land and freshwaters) are inter connected and exchange large amounts of plastics via the air. We can expect a faster degradation of microplastics to nanoplastics in the air (or at the polymer surfaces exposed to the air), and the resulting loads of nano plastics could be concerning
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