Microplastic Emission from Soil-Air Interface

To bridge the gap in understanding soil–air microplastic emissions, here we studied the soil–air transfer mechanism of microplastics with laboratory simulations using microplastic particles varying in size from 1 to 5000 μm. Our findings indicate that the size and shape of the microplastics together with the soil type and moisture levels are major determinants of the microplastic enrichment ratio (ER) in dust, overshadowing the role of polymer types. Notably, microplastic pellets larger than 20 μm do not enrich in dust, while microplastic fibers, even those as large as 500–5000 μm in length, do enrich in dust. Based on our ER measurement, the global microplastic size distribution in soil and dust aerosol production flux, we made a preliminary bottom-up assessment of global soil microplastic emissions of 480.4–1217 kilotons/year. Our pioneering findings on the global atmospheric soil–air microplastic flux provide insights that could guide the future development of a more precise microplastic emission inventory.