The Universitat de Girona (UdG) recently showcased groundbreaking research at the 15th International Symposium on River Sedimentation (ISRS), held in Florence from September 5th to 8th, 2023. The ISRS, a triennial event initiated by the Chinese Hydraulic Engineering Society (CHES) with the support of UNESCO, serves as a premier forum for the exchange of ideas, research results, and techniques related to sediment study and management.

Dr. Marianna Soler, representing the UdG, delivered an insightful presentation on her research titled "Gravity Currents as a Pathway to Segregate Transport of Microplastics." This study, conducted in collaboration with Dr. Jordi Colomer and Dr. Teresa Serra from the Department of Physics at UdG, and Dr. Florian Pohl from the School of Biological and Marine Sciences at the University of Plymouth, delves into the mechanisms through which gravity currents facilitate the distribution and deposition of microplastics in aquatic environments.

Background and Motivation

The pervasive issue of environmental pollution from microplastics has garnered significant attention due to its detrimental effects on marine and freshwater ecosystems. With plastic production escalating from 250 million tons in 2009 to 390.7 million tons in 2021, an estimated 2-5% of these plastics eventually find their way into oceans, exacerbating pollution concerns. Soler’s research focuses on understanding how turbidity currents—a type of gravity current laden with sediments—act as vectors for microplastic transportation and deposition.

Experimental Approach

The experiments were conducted in a 4-meter long methacrylate flume designed to simulate natural water flow conditions. This setup allowed the researchers to observe the behavior of sediment-microplastic mixtures under controlled conditions. The experiments utilized sediments composed of 80% silica and 20% heavy metals, alongside various microplastics including melamine, PVC fragments, and PET fibers.

The study employed different initial sediment concentrations (Co = 1.0, 2.0, 3.0, 4.0, and 5.0 g/L) to simulate varying turbidity current intensities. The experimental runs revealed that higher sediment concentrations led to further transportation of microplastics, demonstrating a clear segregation pattern based on the settling velocities of different microplastics.

Findings and Implications

Soler’s research identified that denser gravity currents transported microplastics to greater distances, with microplastics like melamine and PVC fragments being deposited further from the source at higher sediment concentrations. This segregation is critical for understanding the spatial distribution of microplastics in aquatic environments.

The findings highlight the role of turbidity currents in the environmental dispersion of microplastics, emphasizing the need for further investigation into sediment dynamics to mitigate pollution. The insights gained from this study are pivotal for developing strategies to manage and reduce microplastic contamination in water bodies.

The participation of the Universitat de Girona at ISRS 2023 underscores the institution's commitment to addressing environmental challenges through scientific research. The contributions of Marianna Soler and her colleagues provide valuable knowledge that can inform future policies and practices aimed at preserving aquatic ecosystems from the burgeoning threat of microplastic pollution.

For more detailed information on this study, please refer to the article "Gravity Currents as a Pathway to Segregate Transport of Microplastics" presented at ISRS 2023.