We investigate passive transport of inert and reacting substances in fluid flows. As for inert transport we mainly focus on the Lagrangian properties. In particular, we study the single particle dynamics in order to investigate the conditions for observing standard or anomalous diffusion. This allows for understanding the large scale motion of the concentration field. As for reactive transport we discuss the asymptotic properties of the front propagation in the case of cellular flows. The goal is to investigate the front speed dependence on the stirring intensity. Moreover, we discuss front propagation in the geometrical optics limit, i.e., the limit of very fast reaction and sharp front. We shall also comment about the role of Lagrangian chaos on the propagation properties.
