Study of Pollution Transport Based on a Dynamical System Theory in Xiangshan Bay, China

Understanding the characteristic of pollution transport is essential for protecting the water quality in coastal areas, or bays. Lagrangian Coherent Structure (LCS), a concept from dynamical system theory, is applied to study pollution transport in Xiangshan Bay located in the middle coast of Zhejiang Province in China with strong tidal dynamics. The LCSs of flow field are defined as the attracting or repelling material curves in Finite-time Lyapunov exponent (FTLE) fields. The FTLE fields are computed based on the velocity data of the three-dimensional, high resolution hydrodynamic model developed for Xiangshan Bay. The LCSs can reveal the accumulation or dispersion characteristics for different waters in Xiangshan Bay. Further, some particle tracking experiments were conducted to study how these curves affect pollution transport through analyzing the Lagrangian trajectories. The main transport patterns in Xiangshan Bay are given finally. The results can help optimizing the sewage draining outlets location to make the pollution leave the bay more efficiently and managing the coastal pollution.