Transport of toxic arsenic compounds in heterogeneous soils could be affected by rate limited processes including kinetic sorption and/or two region flow. In this study, saturated column experiments were conducted to investigate the transport of arsenite [As(III)] in soils having different properties. Flow interruptions were carried out during conservative tracer (tritium) and reactive As(III) input pulses to evaluate the extent of physical and chemical non-equilibrium conditions. Breakthrough curves (BTCs) from As(III) transport experiments displayed diffusive front followed by extensive tailing, which is indicative of the dominance of rate-limited processes. Sharp decrease/increase in As(III) concentration after flow interruption (no flow) further verified the extensive of non-equilibrium conditions. Observed BTCs were described with a multiprocess non-equilibrium model, where physical non-equilibrium was represented with mobile-immobile two-region model (MIM) and the chemical non-equilibrium was accounted for based on second order two site model (SOTS). The transport of As(III) was controlled by kinetic sorption reactions, whereas diffusion to immobile region within soil aggregates contributed relatively little to the transport of As(III).