Research On Numerical Simulation Of Marine Chemicals Spill Based On GIS

With the increasing transportation of liquid chemicals in bulk by ships, the risk of the chemicals spill is getting higher and higher. So the reasonable numerical modeling of the spilled chemicals at sea is a key technique for the risk assessment and contingency decision-making. By taking advantage of the GIS's capacities of analysis and-visual expression on spatial data, the paper develops the numerical simulation system to calculate and display the fates and behaviors of spilled chemicals at sea.Based on the analysis of the State-of-the-art numerical modeling on the tidal current, spreading of pollutant in the water column, and the application of the GIS in the marine science, the Monte-Carlo method is used to established the individual numerical model of emission in the air, advection on the water surface and dilution in the water column for different type of chemicals according to the chemical and physical character of each type of spilled chemicals. And a water-air interactive model is studied to consider the physical transfer between the water and air. So the fate and behaviors of the spilled chemicals at the sea and in the air can be simulated simultaneously.To provide the prevail conditions of the tidal current and the wind, the exoteric boundary condition using the data from exoteric station is established by conciliatory method, in which the movable boundary is dealt with by "dry-wet" method. Then the simulation models are computed by ADI method. The unison constants are saved in the form of layer databases for the aim to predict tidal current quickly. The wind field at theheight of 10 meters can be obtained by inserting the observatory data, and the wind field at the other height can be extrapolated using the diagnostic method.To promote the application of the numerical models, the GIS component (MapX)and an Object-oriented Programming Environment (Visual Basic ) are used to integrate the numerical models and GIS as a software system. With the help of the GIS module, the conversions of projection and coordinate, the formation of calculation grid and isoclines, and other functions can be approved. And the simulation results of the fate and behaviors of the spilled chemicals in space and time can be visually expressed.In the end, the numerical modeling system is applied to simulate the "3.24" oil spill accident happened in the Pearl River Estuary. The correspondence between the simulation results and the fact indicates that the numerical models and the system are feasible to simulate the behaviors of the spilled chemicals.