Microplastic Trapping Efficiency Within a Low-cost Sediment Trap

Uncovering complex microplastic interactions in fluvial systems is critical for taking action to remediate these environmental pollutants. A low-cost sediment trap has been developed for deployment in shallow creeks and rivers to capture microplastics. To test the trapping efficiency of this design, a flume was constructed to move plastics of different chemical compositions, shapes, and diameters through the trap. The sediment trap was tested in experiments, with (1) a high discharge rate (2.30 m 3 /hour) and (2) a low discharge rate (1.15 m 3 /hour). A total of eight hundred microplastic particles, one hundred particles of eight different types of fibers, fragments, nurdles, and foam spheres, were introduced in the flume for each experiment. Each experiment trapped approximately one-quarter of the plastics introduced in the sediment trap (high discharge = 25.13%; low discharge = 21.75%). The high discharge rate experiment proved to be most effective in trapping small diameter (1-2 mm) foam spheres (69%), while being less effective at trapping large ( >4 mm) foam balls (4%). The low discharge rate experiment proved to be the most effective at trapping thin (0.2 mm-diameter, 3-cm long) fishing line (43%), and, similar to the higher discharge experiment, least effective in trapping the large foam balls (3%). The results of these experiments aid in understanding the trap’s microplastic capture efficiency across different sizes of microplastic traveling at varying rates. Future work will include measurement of microplastics captured by deposition from overlying flow into the trap and will consider the role of sediment in this system.