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Spread of Bollution by Dispersive Groundwater Flow

A study is made of the transport of pollution in groundwater. The probability that in groundwater a contaminated particle crosses the boundary of a protected zone is computed by asymptotically solving the Dirichlet problem for the backward Kolmogorov equation describing the random motion of the particle. The randomness in the displacement of the particle is due to the dispersive properties of the flow. The expected arrival time at the boundary is computed from a corresponding nonhomogeneous Dirichlet problem.