144-3 Temporal Microplastics Analysis of Lady Bird Lake, Austin, Texas Sediments: A Reflection of Austin’s Urban Growth

Session: Microplastics in the Environment (Posters)

Poster Booth No.: 36

Presenting Author:

Danielle Zaleski

Authors:

Zaleski, Danielle¹, Olariu, Cornel², Davis, Marcy³, Bellinger, Brent⁴, Duncan, Daniel⁵

(1) Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX, USA, (2) Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, TX, USA, (3) UT Institute for Geophysics, Austin, TX, USA, (4) City of Austin Watershed Protection Department, Austin, Texas, USA, (5) UT Institute for Geophysics, Austin, Texas, USA,

Abstract:

In a fast-growing metro area like Austin, Texas, microplastics pollution (particle size 1 μm to 5 mm) is an ever-growing concern to environmental health; however, the impact of rapid urban expansion on microplastics in Austin's waterways was only recently assessed. We present microplastics concentration data from a 3 m-long sediment core from Lady Bird Lake in downtown Austin, which was analyzed to understand variations in microplastics concentration with depth. We hypothesize that microplastics amount in the sediment core from an urban lake will increase from the oldest sediment to the youngest sediment, mirroring Austin’s population growth. Microplastics were separated from 100 g of core sediment at 10-cm intervals. Particles were inspected, counted, and measured using a microscope and ImageJ software. Microplastics were found in every sample; tire and road wear particles (TRWP) were the most abundant type of microplastics with hundreds to thousands of particles per 100 g sample. Fibers and fragments were also present in almost every sample, with fiber amounts of 2–30 particles/100 g, and fragments of up to 148 particles/100 g. Microplastics amounts increased in the core from bottom (oldest sediment) to the top (youngest sediment) as hypothesized, with a significant increase in TRWPs (hundreds to thousands) and fragments (tens to >hundred) at 70 cm depth. Austin’s rapid population growth was coupled with an increase in the density of road networks and impervious surfaces, contributing to an increase in microplastics runoff into local waterways. The abrupt microplastics increase at one depth suggests that there may have been a significant change in human activities, altering the urban lake catchment area and/or water and sediment circulation. Several large flood events occurred after 2000, but it is not clear how floods might change the microplastics entrapment in the lake. Sediment age dating (in progress) will help correlate major urban and/or natural events (e.g., development, flooding) in Austin with microplastics increases in core sediments, which may inform future mitigation and monitoring strategies.

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

doi: 10.1130/abs/2025AM-6422

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