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Sedimentary Characteristics of Microplastics Transported by Turbidity Currents in a Straight Canyon Topography
Qingsheng Meng, Xiaotian Xie, Yang Lu, Heyu Yu, Guangwei Cheng and Xiaolei Liu

The advancement of ocean observation technology has confirmed that submarine canyons are important sedimentary sites for microplastics. Turbidity currents serve as a medium for transporting microplastics through submarine canyons to the deep sea. However, the transport and deposition of microplastics in these canyons by turbidity currents remain unclear. This study, through physical model experiments, explores how the initial conditions of turbidity currents affect the distribution of microplastics in a canyon topography. Results reveal that different concentrations of turbidity currents create varying depositional patterns along the middle to the upper reaches of the canyon. At low concentrations, uniformly distributed crescent-shaped structures are formed, whereas at high concentrations, the deposits are irregularly shaped and tend to migrate toward the head of the canyon. Microplastics are predominantly deposited in areas with wavy sedimentary topography, and in situations with low turbidity current concentrations, abundant microplastics are exposed and accumulated. Additionally, the retention rate of microplastics in 6% volume concentration of turbidity currents is considerably higher than that in 1% volume concentration, and high flow rates promote the migration of microplastic enrichment areas along the canyon. The maximum enrichment zones of microplastics are always located in areas with wave-shaped topography where the sediment particles are large, making them the main deposition zones for microplastics. This research provides valuable insights for predicting the accumulation sites of microplastics in submarine canyons and their effects on the ecological environment.

Keywords: Microplastics, retention rate, submarine canyon, turbidity current, environmental impact, physical modeling test