144-5 Cross-Channel Distribution of Microplastics and Other Anthropogenic Microparticles in Stream Sediment

Session: Microplastics in the Environment (Posters)

Poster Booth No.: 38

Presenting Author:

Natalie Hernandez

Authors:

Hernandez, Natalie F¹, Sanders, Julia M², Hasenmueller, Elizabeth³

(1) WATER Institute, Saint Louis University, Saint Louis, MO, USA, (2) Saint Louis University, Earth, Environmental, & Geospatial Science, Saint Louis, MO, USA, (3) Saint Louis University, Earth, Environmental, & Geospatial Science, St. Louis, MO, USA,

Abstract:

Streams are increasingly studied to understand their role in transporting microplastics and other anthropogenic microparticles to downstream habitats. However, sampling of stream cross-sections remains uncommon, and, consequently, the influence of stream geomorphological features (e.g., point bars, cut banks) on the lateral distribution of anthropogenic microparticles stored within sediment is not well understood. Our research therefore investigates the distribution of anthropogenic microparticles (including microplastics) in the sediment of an urban stream’s channel and floodplain features. We sampled the sediment of Deer Creek near St. Louis, Missouri, United States, along two cross-channel transects that included sites in the thalweg (n = 2), across the surfaces of point bars (n = 9), down the vertical faces of cut banks (n = 8), at the surfaces of vegetated banks (n = 2), and on the surfaces of the floodplain (n = 7). Anthropogenic microparticle content in the stream’s sediment ranged 19.9 – 483.9 counts/kg and included mostly clear fibers (83%), followed by black fibers (7%), then smaller percentages of less common color-morphology combinations (< 5% each). We also found that anthropogenic microparticles were largest in the thalweg sediment (1587.5 ± 1070.0 µm) and smallest in the floodplain sediment (701.0 ± 180.7 µm). Concentrations of anthropogenic microparticles were highest in the floodplain (248.5 ± 170.2 counts/kg), followed by the vegetated banks (245.8 ± 230.8 counts/kg), the cut bank faces (103.1 ± 100.3 counts/kg), the point bars (68.6 ± 60.4 counts/kg), then the thalweg (30.0 ± 14.2 counts/kg). The anthropogenic microparticle content at the land’s surface had a moderate, positive trend with site surface elevation that was significant (Spearman’s ρ = 0.42, p < 0.05). The elevated floodplain setting may store high amounts of small-sized anthropogenic microparticles compared to the other stream geomorphological features because, during flood events, reduced flow velocity and carrying capacity promote deposition as the stream overtops its banks. Further work will incorporate anthropogenic microparticle material type analyses and sediment properties (e.g., grain size, organic matter content) to clarify the controls on anthropogenic microparticle distributions across stream geomorphological features.

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

doi: 10.1130/abs/2025AM-8778

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