LINEAR EQUILIBRIUM ADSORBING SOLUTE TRANSPORT IN PHYSICALLY AND CHEMICALLY HETEROGENEOUS POROUS FORMATIONS .2. NUMERICAL RESULTS

Numerical Monte Carlo simulations were conducted to assess dispersion of reactive solutes in two-dimensional physically and chemically heter ogeneous porous media, using random fields with assigned correlation s tructure for hydraulic conductivity and linear adsorption coefficient. Conditions under which linearization of adsorption is valid are discu ssed. Lognormal distributions of hydraulic conductivity and adsorption coefficient were assumed. Calculations have been performed for positi ve and negative correlation between hydraulic conductivity and adsorpt ion coefficient, and for uncorrelated cases. Effects of varying differ ent properties including mean and average sorption coefficient, physic al and chemical integral scale, and variance of hydraulic conductivity on dispersive behavior are shown. A larger mean sorption coefficient enhances plume spreading in uncorrelated and in negatively correlated cases. In positively correlated cases, counteracting effects of physic al and chemical heterogeneity play an important role. The outcome of t hese counteracting effects depends on the mean, variance, and integral scales of the spatially variable properties. The analytical solutions , derived in paper 1 (Bellin et al., this issue), reveal a good agreem ent with the numerical results in a significant range of heterogeneiti es. The generally surprisingly good agreement of the analytical soluti ons with the numerically obtained results can possibly be attributed t o opposing effects of nonlinearities neglected in the derivation of th e analytical solutions. In the case of strong physical heterogeneity t he analytical solutions perform slightly better than in the case of st rong chemical heterogeneity.