Linear systems approach to subsurface pollutant transport analysis
Liu, Clark C.K., C. Ji, and D. Neupane
Comprehensive physically based models of chemical transport in soils consist of two nonlinear partial differential equations. An exact analytical solution for these equations is difficult to derive. A numerical solution, on the other hand, produces numerical dispersion and leads to unsatisfactory modeling results. For nonconservative chemicals in adsorptive soils, physically based modeling becomes even more complicated. Simplified models such as mobility index models have been proposed and used, but they are too simple to provide any in-depth understanding of the transport phenomenon. This study shows that by using a linear systems approach, transport characteristics of field soils can be simply described by an impulse response function. The fate and transport of chemical residues in the soil can then be readily determined by convolution integration. This study also shows that the impulse response function of a soil transport system takes the form of a gamma distribution function. Two multiple regression equations, which relate the two parameters of a gamma distribution function with the soil’s basic properties, were derived.