A mechanistic approach to evaluating atmospheric deposition of micro- and nanoplastic particles

Atmospheric deposition plays an important role in the global distribution and long-range transport potential of micro- and nanoplastic particles (MNPs). However, our mechanistic understanding of contributing processes remains limited. While similarities in wet and dry deposition processes can be expected between MNPs and well-studied natural and anthropogenic aerosols (e.g. mineral dust, pollen, black carbon), no holistic theoretical framework currently accounts for specific MNP properties and their inherent heterogeneity. Here, we present an integrated mathematical description of atmospheric particle transport which incorporates MNP properties (size, shape, density and surface characteristics, including effects of environmental ageing) based on theory and empirical data. We find that estimated MNP half-lives in air can range from seconds to weeks, depending on MNP characteristics, land surface type, surface wind speed, atmospheric stratification and precipitation. MNPs with diameters of around 1 µm and fibres have highest potential for long-range atmospheric transport.