We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
The effects of stream bed motion and fiber length on microplastic deposition
Summary
Scientists studying how microplastic fibers move through streams and rivers found that when the streambed itself is stirred up (like during heavy flow or storms), plastic fibers get swept back into the water instead of settling into the sediment—and longer fibers are more likely to stay buried when the streambed is calm. This matters because it helps explain where microplastic pollution actually accumulates in waterways, which affects how much of it ends up in the food chain (via fish and other aquatic life) and eventually on our plates.
• MP fiber deposition under stationary and moving bedforms was evaluated using a flume. • MP fibers deposited faster and with minimal resuspension under stationary bedforms. • Resuspension of MP fibers under moving bedforms dominated the deposition processes. • Increasing the lengths of MP fibers resulted in more deposition under moving bedforms. • The MP fiber length did not influence deposition under stationary bedforms. The key processes controlling the transport and deposition of microplastics (MP) in streams and rivers remain poorly understood, particularly under conditions with moving sediments. Experiments were conducted in a 6 m-long and 0.2 m-wide stainless-steel recirculating flume filled with 25 cm of sand (median grain size of 0.6 mm) and water. We conducted two main experiments at stream water velocities of 13 and 53 cm/s, which resulted in stationary and moving bedforms, respectively. MP particles were added to the stream water, and the rates of MP deposition were determined by monitoring the decrease in their concentration over time. The tested MPs included polypropylene (PP) fibers with a diameter of 25 μm and lengths of 25, 100, 200, and 2000 μm. We also used carboxylated polystyrene (PS) microspheres (1 μm) that served as a reference particle. MP fibers deposited faster and with less resuspension under stationary bedforms as compared to moving bedforms. Furthermore, increasing the lengths of MP fibers resulted in more deposition under moving bedforms but did not have a significant effect under stationary bedforms. In contrast to the fibers, the microspheres had approximately the same amount of deposition under stationary and moving bedforms at the end of the experiment. Understanding and identifying key processes that control MP deposition in streams with moving bedforms will enhance our ability to predict their transport mechanisms, providing also crucial insights for evaluating risks to benthic organisms.