Unraveling Microplastic Deposition in Rivers Through the Lens of Sedimentary Processes

River networks are the major pathways for microplastic (MP) transport from terrestrial environments to oceans. However, the ability to quantify the water–sediment exchange of MPs, locations of deposition, and the time scales over which burial occurs is limited and thus often our estimation of where MP deposit is biased. To fill this gap, previous work on processes that control MP deposition will be briefly reviewed, with the aim of enhancing our understanding of the dynamic interplay between flow, sediment transport, and MP deposition. In addition, results from flume experiments and a numerical model showed that the maximum deposition efficiency and deposition depth were found for sediment with high hydraulic conductivity and slow-moving stream water velocity. Also, we found that the exchange of water and particles due to sediment motion leads to burial and potentially long-term deposition of MPs that initially were not expected to enter the bed due to size exclusion. However, increasing celerity (i.e., speed of bed motion) reduces the depth of MP deposition in the streambed and reduces deposition efficiency due to resuspension. The burial of MP beneath the moving fraction of the bed provides a mechanism for long-term accumulation and may explain resuspension events characterized by high MP loads during floods. It is argued that incorporating data on MP distribution in riverbeds with fluvial geomorphological and particle transport models will improve the current evaluation of MP transport in river networks and their burial residence time distribution.

Presentation Preference: Oral

Primary Presenter: Shai Arnon, Ben-Gurion University of the Negev (sarnon@bgu.ac.il)

Authors:

Shai Arnon, Ben-Gurion University of the Negev  (sarnon@bgu.ac.il)

Yoni Teitelbaum, Ben-Gurion University of the Negev  (ytbaum@gmail.com)

Verena Sturm, Ben-Gurion University of the Negev  (sturmve@post.bgu.ac.il)

Eshel Peleg, Ben-Gurion University of the Negev  (eshelp@post.bgu.ac.il)