Abstract

The coastal area of Daya Bay (DYB) is home to important petrochemical industry bases and nuclear power plants in South China. Understanding the water transport and pollutant migration paths in DYB is crucial for ensuring the marine environment and ecological safety of this region. With the synergy of several water quality surveys and ocean current observations, this study investigates the seasonal migration characteristics of pollutants in DYB in 2015. The results show good consistency between the spreading paths of pollutants indicated by the Chemical Oxygen Demand (COD) concentrations and the spatial patterns of residual currents in August and November 2015. Specifically, the residual currents in August 2015 exhibit a cyclonic circulation pattern, corresponding to the counterclockwise expansion of three high COD centers within the DYB. By November 2015, the residual currents weaken significantly and exhibit a slightly anticyclonic pattern, and the simultaneous COD concentration tends to extend clockwise. The anticyclonic residual circulation strengthens in January and may remain until the spring season, resulting in a clockwise expansion of high COD waters in May. The pollutant migration characteristics in winter and spring still require further clarification due to the lack of synchronous observations during these seasons. These observations provide valuable references for numerical simulations and predictions of pollutant migrations in DYB.

Keywords:Daya Bay; Pollutant migration paths; Residual current; Chemical oxygen demand