The coastal area in the northern South China Sea (nSCS) is one of China’s most economically active regions. The fast-growing industry of marine sector and the shipping has increased the probability of oil spill accidents. An oil spill is a usually unexpected incident that is harmful to the ecological environment and marine organisms of the coastal area. As a result, utilizing a numerical model to simulate the fate and transport trajectory of spilled oil and to assess the potential risk of an oil spill accident to the coastal marine environment is of great necessity. The present study aimed to examine the impact of the risk of oil spills on the coastal environment in the nSCS. We built a hydrodynamic model and an oil spill dispersion model based on MIKE21 FM to study the tidal dynamics and oil spill dispersion in the coastal area in the nSCS. Moreover, the stochastic approach was used to simulate and predict the fastest arrival time and the probability distribution of the pollution of the oil film to the surrounding environment in the coastal regions of the nSCS. We examined the mechanisms for the influences of tides and wind on the fastest arrival time of oil film and the spatial distribution of the pollution probability of oil spill incidents at different locations in the nSCS based on the model. The results showed that the wind direction has a dominating effect on the direction of the oil dispersion. Due to the differences in the tidal dynamics in different regions, the migration and dispersion of the oil are also affected by the tidal current. This research provides guidance on the risk assessment of oil spill accidents for marine environmental management.

The impact of thermal pollution caused by cooling water discharge of power plant on the surrounding marine ecology has been a hot issue in oceanographic research. To reveal the distribution pattern of cooling water discharge of Daya Bay Nuclear Power Plant in summer and the impact on the surrounding marine environment, this research established a high-resolution three-dimensional (3D) numerical model based on ECOMSED in the Daya Bay. The model results are consistent with the observations on the distribution of tide level and temperature. The simulated horizontal distribution of temperature rise is consistent with the distribution trend of remote sensing images. The study showed that the stratification of the Daya Bay water is stronger in summer. The cooling water mainly spreads in the surface layer, and the temperature rise in the bottom layer is not apparent. Quantitative analysis showed that around 18.8-21.6 km2 of the area has 1°C surface temperature rises. The area of temperature rises that exceeds 2 °C is between 6.2 and 8.1 km2. The area of temperature rises that exceeds 4 °C is between no more than 1.2 km2. The area with a bottom temperature rises of 1 °C does not exceed 2.2 km2, and there is no area that has a bottom temperature rise over 1 °C. The tidal dynamics process influences on the dispersion of cooling water discharge from Daya Bay Nuclear Power Plant, where the influence is more significant in the spring tide period than in the neap tide period. Our findings are consistent with previous researches.

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