Tracking Microplastics Across the Streambed Interface : Using Laser‐Induced‐Fluorescence to Quantitatively Analyze Microplastic Transport in an Experimental Flume

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Boos, Jan-Pascal ; Gilfedder, Benjamin Silas ; Frei, Sven:
Tracking Microplastics Across the Streambed Interface : Using Laser‐Induced‐Fluorescence to Quantitatively Analyze Microplastic Transport in an Experimental Flume.
In: Water Resources Research. Bd. 57 (2021) Heft 12 . - No. e2021WR031064.
ISSN 1944-7973
DOI der Verlagsversion: https://doi.org/10.1029/2021WR031064

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Abstract

Rivers and streams are a primary transport vector for microplastics (MPs), connecting terrestrial sources to marine environments. While previous studies indicated that pore-scale MPs can accumulate in streambed sediments, the specific MPs transport and retention mechanisms in fluvial systems remain poorly understood. As part of this technical note, we present a novel method for a quantitative analysis of the spatiotemporal transport and retention of pore-scale MPs in an experimental flume. A continuous mass balance for MPs in surface water was achieved using two online fluorometers, while a laser-induced Fluorescence-Imaging-System was developed to track and quantify the spatial migration of MPs through the streambed sediments. The detection limit was < 1 µg/L for 1 µm polystyrene microbeads with the fluorometers and 3 µg/L for the Fluorescence-Imaging-System. The system was able to quantitatively track the advective transfer of MPs into the streambed sediments: a process that has yet not been observed experimentally. Results showed that MPs infiltrated into the streambed sediments up to a depth twice the bedform amplitude. This work provides a novel experimental method to quantitatively monitor MP transport through porous media and advective exchange of MP across the streambed interface.