Assessing Atmospheric Transport of Microplastics at a Global Scale Using the NASA GISS Model

Abstract:

Microplastics (MPs) have become increasingly ubiquitous in recent years and their long-term impact on the environment is still poorly understood. Accumulating over time within both organic and inorganic material, these substances are postulated to serve as endocrine disruptors, absorbers of toxic substances like heavy metals, and low albedo particulates whose accumulated thermal energy may accelerate ice melt. Researchers have identified MPs in places as remote as the Pyrenees Mountains and the Marianas Trench, yet their means for traveling great distances remain poorly understood. Recent papers have shown they can be transported via global atmospheric and oceanic currents. Climate models such as that developed at the NASA Goddard Institute for Space Studies have been used to trace aerosol transport by either utilizing back propagation techniques to understand the sources of aerosols, or to understand deposition locations and rates given initial release estimates. We investigate the possibility of using the aerosol transport model within the NASA GISS model to perform synthetic experiments concerning the origin of MPs and their transport and deposition. Regions of large MP production were modeled as entry sites for injection of material and a series of sensitivity analyses and synthetic experiments were performed to determine how shape, weight, density, and other properties affect their atmospheric transport. Although we have very few measurements of actual MP deposition, hypothetical characteristics were optimized to build increasingly accurate reflections of their known physical and chemical nature. This analysis demonstrates that tracers in climate models can be used to model MP particulate transport. Further, it provides a methodology and sample test case simulations that others can use once more is known about the actual trajectory of MP dispersion in order to begin to predict future potential deposition. Prediction of MP deposition can in turn be used to better characterize health risks for humans and animals, understand local versus external sources of MPs, and support modeling of ocean-atmospheric interactions. Such information is critical for policymakers to develop legislation to further prevent MP dispersion, as well as for citizens to be informed about the potential threat to their health.