Fig. 4. Examples of measured concentration versus distance profiles for naphthalene diffusion at different soil-water contents () and incubation times (t). The solid lines are model fit to measured data to obtain the D_eff value, while the dotted lines represent model predictions using measured gas and solute diffusivities (Fig. 3) and adsorption K_D (equal to 9.5 cm³ g^-1).