Deposition is the main migration process of low-density microplastic aggregation in lakes. In order to explore the deposition law of low-density microplastic aggregation in Wuliangsu Lake, a microplastic trap was designed and applied to examine the deposition process based on the similarities and differences between microplastics and naturally occurring suspended solids. The deposition processes of different sizes and shapes of low-density microplastic aggregation were quantified in Wuliangsu Lake. The results showed that the deposition fluxes of all types of low-density microplastic aggregation increased with wind speed. The deposition of flux of low-density microplastic aggregations with a similar shape of fiber and with a size ranging from 0.05-0.5, 0.5-2, and 2-5 mm had better correlation with wind speed. The correlation coefficient changed from 0.218 to 0.836. The deposition of flux of low-density microplastic aggregations with a similar shape of fiber, fragment, grain, and film and with size ranging from 0.05-0.5, 0.5-2, and 2-5 mm under different wind speeds at different experiment sites changed from 0-(1458±284), 0-(368±144), 0-(71±37), and 0-(85±65)n·(m2·d)-1, respectively. Furthermore, we found that, when shape was held constant, larger low-density microplastic aggregations were more likely to be deposited, whereas smaller low-density microplastic aggregations were more likely to be transported. When size was held constant, fragmentary low-density microplastic aggregations were more likely to be deposited than fibrous and film microplastic.
Keywords: Wuliangsu Lake; deposition; low-density microplastic aggregation; microplastic trap; wind speed.