Remote Sensing of Microplastic Aerosols Using GRASP Open Spheroid Modeling

CAMILLE TEDDER, Alexandria Johnson, Gouri Prabhakar, Olga Kalashnikova, Purdue University

     Abstract Number: 584
     Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts

Abstract
Environmental pollution by plastics has long been a reason for concern but recently atmospheric microplastics (AMPs) have emerged as a significant area of interest due to their widespread presence in even the most remote regions of the planet. With the increasing number of AMPs comes the need to detect these particles, differentiate them from natural aerosols like dust, and understand their spatial and temporal heterogeneity to help inform environmental, health, and safety policies and studies. Here we work towards an understanding of AMP optical properties to determine their detectability through remote sensing.

Using the GRASP Open Spheroid-package, we have modeled and compared the scattering and polarization properties of three commonly identified AMPs – polyvinyl chloride, polyester, and polystyrene – and four dusts from distinct regions – Beijing, Seoul, Tunisia, and Libya – over a range of wavelengths. Using randomly oriented, polydisperse spheroids provides a more realistic approximation of the optical properties. Additionally, our wavelengths of interest correspond to those used by the Multi-Angle Imager for Aerosols (MAIA), a joint NASA and the Italian Space Agency mission aimed at collecting data on atmospheric aerosol pollutants with a focus on urban areas. In this talk I will discuss how the complex refractive indices of these materials show distinct differences between the absorption of AMPs and dust particles which leads to predicted differences in the amount of forward (0° - 15°) and mid-angle (90° - 120°) scattered light and the degree of linear polarization at mid-angles between AMPs and dusts. While preliminary, this work indicates that remote detection of these particles at optical and near-IR wavelengths may be possible and further studies, including those focused on instrument sensitivity, are needed.