ABSTRACT:

The fate of atmospheric anthropogenic microparticles (i.e., microplastics and other human-made materials < 5 mm) remains understudied. Current research suggests that climate influences deposition fluxes of anthropogenic microparticles from the atmosphere, and, globally, megacities in humid regions have high deposition fluxes. However, atmospheric anthropogenic microparticle deposition fluxes in the comparatively less populated humid subtropical cities of the central United States are understudied. Our study thus analyzes atmospheric deposition of anthropogenic microparticles (including microplastics) at an urban and suburban site in St. Louis, Missouri, United States, over 1 year. Anthropogenic microparticles were found from below our limit of detection up to 312.9 particles/m2/day. The urban site had a significantly higher 101.7 particles/m2/day average deposition flux compared to the suburban site’s average deposition flux of 43.3 particles/m2/day. Microfibers (synthetic and cotton) were the most common morphology, and microplastics (fully synthetic substances) made up 41-49% of the analyzed microparticles. Relative humidity was positively correlated with anthropogenic microparticle deposition flux throughout the year of sampling. In global comparisons, anthropogenic microparticle deposition in the St. Louis region was similar in quantities and types to previously studied humid subtropical megacities despite population differences. Climate might therefore be a stronger driver of atmospheric anthropogenic microparticle deposition than population size.