Quantification of the Emission of Atmospheric Microplastics and Nanoplastics via Sea Spray

There is growing interest in the transfer of micro- and nanoplastics (MNP) to the atmosphere from the ocean via sea spray, and a limited number of studies have quantified this emission. This study addresses the uncertainty surrounding existing global oceanic MNP emission estimates by developing an experimentally based emission parametrization. We conducted systematic laboratory experiments to understand the impact of MNP size, density, and concentration in water on their aerosolization. The results show that the MNP considered in this study, with a diameter of ≤10 μm, can be emitted via bubble bursting, with the aerosolization increasing monotonically with an increase in the concentration in water and decreasing with an increase in the particle size. Floating polyethylene MNP are observed to be less effectively aerosolized than polystyrene MNP dispersed in bulk water. Using the developed emission parametrization, we estimate that the upper limit of yearly MNP oceanic emission is 50.7 (14.2–93.4) quadrillion (1015) pieces year–1 and 1.66 (0.72–4.13) t year–1. The experimental measurements and ensuing parametrization developed in this study are a timely contribution to the atmospheric microplastic modeling community and will help in further constraining the oceanic source of atmospheric MNP and their potential climatic, environmental, and health implications.