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MODELING OF THE EFFECTS OF CYCLIC WATER TABLE FLUCTUATIONS ON FATE OF NAPL GAN-GLIA

The size distributions of the ganglia (assumed to be spherical in shape) are tracked throughout in the model. The dissolved phase of the NAPL is simulated using an advection-dispersion equation which is modified to include ganglia mobilization, biodegradation, and volatilization. A constant rate of l-d ground water flow is maintained in the saturated zone.

The mathematical equation governing the fate of NAPL ganglia is modified to account for a continuous cyclical fluctuation of water table. The movement of the NAPL pool associated with the ground water table fluctuation is assumed to recharge the gan-glia which have been depleted by volatilization in the unsaturated zone, and by dissolution and biodegradation in the saturated zone.

Laboratory results show that this assumption is valid. Using this model, it was possible to predict the ganglia size distribution both in the saturated and unsaturated zones at various stages of ground water table movement, and more importantly the lifetime of the LNAPL pool persistence at the water table.

A sensitivity analysis is conducted and the effects of the rate of ground water table fluctuations on the fate of LNAPLs are demonstrated.

Key words: LNAPL, ground water table fluctuations, ganglia dissolution, biodegradation.