Numerical modeling of COD transportation in Guangxi coastal bays: A short communication

A three-dimensional numerical model of Guangxi coastal hydro-dynamical environment was constructed based on ECOMSED to study the COD transport with fine grid based on latest coastline and bathymetry data. The experiment results showed that the trace of COD was mainly affected by the flood and ebb tide in coastal regions; The area in Qinzhou Bay with COD concentration exceeding 1mg/L, 3mg/L and 6mg/L on the 31th day was 60.5km², 14.8km² and 3.7km² respectively. The corresponding results at Nanliu river estuary was 64.7km², 23.1km² and 0 km² respectively. The COD-polluted water at the Nanliu river esturay spread more widely but no concentration larger than 6mg/L was found, which could be explained by the different topographic conditions in these two places. The vertical distribution of COD transport was approximately the same as in surface, except that the area exceeding 1mg/L decreased slightly in the middle and bottom layer. (paper)