Huang and Hu <2000> developed a nonlocal, first-order, Eulerian theory for the mean concentration of a conservative tracer in a dual-porosity medium. Here the results of Huang and Hu are extended to reactive chemical transport under linear nonequilibrium sorption in both mobile and immobile zones. Similar to Huang and Hu <2000>, a two-zone, mobile and immobile, model <van Genuchten and Wierenga, 1976> is adapted to account for the interregional mass transfer. Hydraulic conductivity in the mobile zone, sorption coefficients in both zones, and interregional mass diffusion rate are all assumed to be spatial random variables to account for the inherent spatial variability of physical and chemical properties of a natural medium. The analytical solution for mean concentration in mobile water is given explicitly in Fourier-Laplace space and numerically converted to real space via a fast Fourier transform method. The results are simplified to conservative transport in a dual-porosity medium <Huang and Hu, 2000> and reactive transport in a one-zone model <Hu et al., 1995> under appropriate conditions. The solution provides a tool to investigate the validity of an effective sorption method, where various chemical sorption and physical mass transfer processes are treated as a sorption process with effective sorption parameters. This study shows that chemical sorption and interregional mass diffusion may be lumped together as an effective sorption process under specific conditions. Generally speaking, however, such simplification will lead to a significant error in prediction of the plume evolution, especially at late travel time. It is also shown that randomness of the interregional mass transfer process will significantly enhance the plume spreading and lead to a more negatively skewed plume. ¿ 2001 American Geophysical Union