Aerosol mass concentrations and dry/wet deposition of atmospheric microplastics at a remote coastal location in New Zealand

This study quantified airborne microplastic concentrations by mass and number counts using both active and passive sampling at a remote coastal location in Southern New Zealand. Seven polymers were quantified using pyrolysis gas chromatography mass spectrometry (Pyr-GC/MS) in atmospheric samples, finding that plastics comprised at least 0.14 % of total suspended particulate mass at the remote coastal site. Air parcel back trajectories suggest that airborne microplastics at the site, observed at an average concentration of 65 ± 6 ng m^-3, have origins from the Southern Ocean. Additionally, the results demonstrate that reporting atmospheric deposition of microplastics by number counts may underestimate the true amount of plastics present in samples, as size limitations associated with microscopic imaging do not allow for quantification of the most abundant sizes and types of environmental microplastics. With current uncertainties related to aerosol formation in the Southern Ocean and the associated impacts on climate forcing, further research is urgently needed on the production of airborne microplastics originating from the Southern Ocean, a possible microplastic reservoir.