Analysis on pollutant accidental discharge in Zhoushan Islands, China.

The water quality diffusion and transport around archipelago have their own uniqueness and complexity. On the basis of multinest 2D mathematical model for currents around Zhoushan Islands, model for water quality prediction was built. The pollutants discharge of Xiaogan Island was taken into consideration and mathematical model for pollutant diffusion and transport in accident discharge was studied. The influence on water quality in different discharge intensity was calculated, which provided scientific basis for the control results. It was observed that the concentration contours of COD(Mn) at 0.03 km(2) in three conditions corresponded to standard discharge at 0.90 mg l(-1), accidental discharge at 1.02 mg l(-1)and extreme discharge at 1.42 mg l(-1), respectively. Although discharge point locates between the archipelago, diffusion of pollutants is rapid for the fast-flowing waters ofZhoushan Islands, that provides good diffusion conditions.