Gravitational Settling of Microplastic Fibers

Description

Airborne microplastic particles may have large impacts on human health and, where deposited, on the environment. Therefore, it is crucial to gain more knowledge about transport and removal mechanisms to investigate their in-situ distribution, including transport to remote regions. Most of the atmospheric transport models consider a particle as a perfect sphere, while non-spherical particles experience a larger drag in the atmosphere, which leads to a reduction of their settling velocity and thus longer atmospheric residence times. Hence, model output and ground-based measurements can differ significantly. In this study, we investigate the gravitational settling of the microplastic fibers, since they are the dominant microplastic shape. We have implemented shape correction factors in the gravitational settling scheme of the Lagrangian transport model FLEXPART v10.4. Using different parameterizations for the shape effect, we have carried out sensitivity studies with FLEXPART and quantified the atmospheric residence time and typical transport distances both for spherical particles and when using the different parameterizations of the shape effects. Sensitivity of deposition patterns to changes in the particle shape have also been quantified. In order to test how reliable the available parameterizations for shape corrections are for the extremely elongated shapes of large fibers (>50 µm in volume equivalent diameter of a sphere), in September 2021 we will also conduct experiments with such microplastics fibers in an aerodynamic vertical wind tunnel that allows determining the terminal settling velocities of the particles. Based on these experiments, the most appropriate parameterization for the shape effect will be selected and, if needed, modified for final inclusion in FLEXPART. This will facilitate more accurate simulations of atmospheric transport of microplastics but will be useful also for simulation of other particles such as dust or volcanic ash.

Publication:
AGU Fall Meeting 2021, held in New Orleans, LA, 13-17 December 2021, id. A44D-03.
Pub Date:
December 2021
Bibcode:
2021AGUFM.A44D..03T

Period	13 Dec 2021 → 17 Dec 2021
Event title	American Geophysical Union (AGU) Fall meeting 2021
Event type	Conference
Location	New Orleans, United StatesShow on map
Degree of Recognition	International