172-2 Urbanization and Humidity Impact Atmospheric Deposition of Anthropogenic Microparticles (Including Microplastics) in a Humid Subtropical City

Session: Urban Geochemistry

Presenting Author:

Authors:

Abstract:

The fate of anthropogenic microparticles (i.e., microplastics as well as other humanmade materials of < 5 mm) that have been suspended in and transported through the atmosphere remains understudied. Current research suggests that climate plays a role in the long-term deposition rates of anthropogenic microparticles, and megacities in humid regions have high levels of microplastic deposition across the globe. However, atmospheric anthropogenic microparticle deposition has not been assessed in the comparatively less-populated humid subtropical cities of the central United States. Our study analyzes atmospheric deposition samples for anthropogenic microparticles (including microplastics) at an urban site and suburban site in the metropolitan area of St. Louis, Missouri, United States, over 1 year. Anthropogenic microparticles in atmospheric fallout samples were found from below our limit of detection (LOD) up to 312.9 particles/m²/day. The urban site had a significantly higher 101.7 particles/m²/day average deposition rate compared to the suburban site’s average deposition rate of 43.3 particles/m²/day. Microfibers were the most common anthropogenic microparticles that we found, and microplastics (i.e., fully synthetic substances) made up 49% and 41% of the material types that were analyzed for the urban and suburban sites, respectively. Polyethylene terephthalate (PET) and cotton fibers were the most prevalent material types. Higher relative humidity enhanced anthropogenic microparticle deposition and was a key factor impacting the temporal fluctuation in anthropogenic microparticle deposition rates throughout the year of sampling. In a global context, the quantities and types of anthropogenic microparticles deposited in the St. Louis region were similar to those observed in previously studied humid subtropical megacities despite population differences. Thus, climate might be a stronger driver of atmospheric anthropogenic microparticle deposition dynamics than population size.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8800

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