The role of pore water flow in solute transport below a rippled sediment bed in a coastal environment is investigated. Based on the velocity field induced by the passage of gravity waves, a steady-state transport equation is solved numerically over a range of field conditions. A consumption term governed by first-order kinetics, a constant diffusivity and a constant boundary concentration slightly above the sediment-water interface are assumed in the two-dimensional continuum model. Significant spatial variations in concentration are found when there is an appreciable pore water flow. The concentration below a ripple trough can be many times higher than that at the same depth below a crest, and the concentration gradient in the horizontal can be of the same order of magnitude as that in the vertical. At high advective transport, a region of uniform concentration is found immediately below the ripple surface away from the crests. The rate of consumption over the sediment layer is compared with the corresponding rate in the absence of advective transport. Their ratio increases monotonously with the ripple slope and the ratio of the magnitudes of advective to diffusive transport and can reach up to 5 even for a relatively mild ripple slope of 0.1. As the magnitude of advective transport depends on the prevalent wave conditions, the rate of consumption and the distribution of solute concentration can vary appreciably with time. These results suggest that hydrodynamic conditions, sediment characteristics, and surface topography should be integral parts of field measurements of the distribution and flux of solutes in coastal sediments. ¿ American Geophysical Union 1993