Based on the unstructured grid MIKE 3D model with the finite volume method

the 3D tidal and water quality numerical model was used to simulate the marine environmental capacity of COD

DIN and oil in the main discharge areas in the Beibu Gulf Economic Zone

China. Compared with the potential future discharges of these three types of pollutants according to the planning scenario around the Gulf

the available level of marine capacity was also discussed. The results indicated that environmental capacity of COD

DIN and oil in the Gulf were 221 267.1

23 058 and 5 297.2 t/a

respectively. Due to the good hydrodynamic diffusing condition

the marine environmental capacities of discharge areas in Yangpu and Bohe were relatively large. The environmental capacity of DIN was seriously overloaded

which leaded to 25% and 33% of the discharge areas overloaded in 2015 and 2020

respectively.