Estimating the emission of microplastics from urban surfaces into the atmosphere using the PI-SWERL

Microplastics (MPs) are a global concern, with the atmosphere being a key pathway for their transport. Understanding their sources is crucial for controlling MP dispersion. This study examines MPs on urban surfaces and their transport through wind erosion using a Portable In Situ Wind Erosion Laboratory (PI-SWERL) under two wind shear conditions. Material was collected in Coimbra, Portugal, from fourteen locations associated with different land uses. MPs number and types were determined with a stereomicroscope and micro Fourier Transform Infrared Spectroscope (μ-FTIR), respectively. MP concentrations in soils ranged from 16 ± 4 particles•g⁻¹ to 327 ± 494 particles•g⁻¹. Emission fluxes ranged from 5 ± 1 particles•m⁻²•s⁻¹ to 28 ± 4 particles•m⁻²•s⁻¹, higher than previous reports. At 4000 revolutions per minute (RPM), enrichment ratio was 3 ± 17 MPs, and at 6000 RPM, 2 ± 6 MPs. A light wind can erode a significant amount of MPs. Light density MPs smaller than 200 μm eroded more easily. Emissions were highest on asphalt (22 ± 9.5 particles•m⁻²•s⁻¹) and lowest on grass (8 ± 8.25 particles•m⁻²•s⁻¹). Grass may help control MP dispersion. These findings can inform MP transport models and policies to mitigate contamination.