144-2 Microplastic Separation from Stream Sediments: A Sustainable, Overflow-Based Density Extraction Method

Session: Microplastics in the Environment (Posters)

Presenting Author:

Authors:

Abstract:

This study explores an environmentally conscious method for isolating microplastics (MPs) from stream sediments. The goal of this work is to establish a low-cost, sequential separation technique that allows for the identification of MP types based on density, without requiring expensive equipment or hazardous chemicals. 

To achieve this goal, MP samples representing six plastic types (PET; HDPE; PVC; LDPE; PP; and PS) were created by cutting common consumer plastic products into ~1 x 1mm pieces. These fragments were specifically chosen for their distinctive colors, which allowed us to identify plastic types with the naked eye. Ten pieces from each MP type were added to pre-cleaned sediment to simulate contaminated field samples. Our protocol begins with a DI water treatment (~1.00 g/cm³), which effectively recovered 100% HDPE (#2), LDPE (#4), PP (#5), and low-density PS (#6) particles. The MP pieces were collected using an overflow method rather than traditional filtration. This overflow method requires less materials, reduces handling, and yields efficient separation of MPs. Subsequent treatments used NaCl (~1.03 g/cm³) and glycerin (~1.26 g/cm³), which effectively separated 100% of high-density PS (#6) particles. To isolate higher density plastics, such as PET (#1) and PVC (#3), we tested potassium nitrate (~2.11 g/cm³). Although environmentally friendly and dense enough for separation, KNO₃ solutions crystallized too quickly to achieve an appropriate density to be effective for isolating PET and PVC particles. 

By using accessible and non-toxic materials in a sequential extraction, our protocol avoids the degradation of MP particles (e.g., ZnCl solutions) while remaining available to the broader public. With the method established, we will next apply it to natural field samples collected from the St. Joseph River in Elkhart County, IN to assess MP contamination.

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

doi: 10.1130/abs/2025AM-5280

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