COMPARISON OF MOMENTS FOR CLASSICAL-FICKIAN, QUASI-FICKIAN, AND CONVOLUTION-FICKIAN DISPERSION OF A CONSERVATIVE TRACER

Transport moments up to fourth order for convolution-, quasi-, and cla ssical-Fickian dispersion of a conservative tracer are presented and c ompared. Convolution-Fickian yields a non-Gaussian distribution while quasi- and classical-Fickian result in Gaussian type distributions reg ardless of the distribution of a stationary velocity field. The first and second central spatial moments are the same for convolution- and q uasi-Fickian dispersion, while the third and fourth central moments di ffer.