Fine micro- and nanoplastics particles (PM2.5) in urban air and their relation to polycyclic aromatic hydrocarbons

Microplastics and nanoplastics have been reported in nearly all environmental compartments, the dataset about their contributions and their role as a sink and carrier for other hydrophobic compounds in the atmosphere however is limited. This study presents, for the first time, atmospheric concentrations of ultrafine microplastics and nanoplastics (UFMNP) on the single polymer level and their correlations with atmospheric concentrations of 23 polycyclic aromatic hydrocarbons (PAHs). Measurements of UFMNP in ambient particulate matter (PM2.5) were performed for an urban sampling site in Graz, Austria. During the sampling period of 02.01. - 31.03.2017 the average UFMNP concentration was 238 ng/m3, reaching up to 557 ng/m3. This accounts for an average contribution of 0.67% to PM2.5mass and 1.7% of organic matter. The individual polymer types were polyethylene terephthalate (PET), polypropylene (PP) and polyethylene (PE), which sum up the most demanded polymer types in Europe. PET was found to be the most prominent polymer in the urban samples contributing to 50% of the overall UFMNP mass, followed by PP (27%) and PE (23%). However, the relative contributions vary with time. PET was observed during the entire time period, while PP and PE were quite variable and linked to the origin of the air masses. A possible carrier function of PP and PE for selected micropollutants can be deduced from the significant monotonic correlations between these polymers and selected PAHs. High correlations were predominantly found for low molecular weight congeners and correlations were more pronounced than those investigated for PAHs and other constituents of PM2.5, i.e. elemental carbon and organic matter again pointing to special interactions of those emerging pollutants.