The effect of spatial variability in geochemical and hydrologic parameters on the transport of surface-reactive solutes in ground-water systems is being investigated in a shallow, sand and gravel aquifer on Cape Cod, Massachusetts. The focus of the study is to identify the geochemical properties controlling metal-ion sorption and to describe their spatial variability. The spatial variability of hydraulic conductivity estimated from grain-size distribution measurements also is being studied. The results will be used in conjunction with tracer-test studies of metal transport conducted at the site to develop coupled solute transport and reaction models that incorporate the observed spatial variability in geochemical properties used to estimate sorbent abundance, metal sorption coefficients, and hydraulic conductivity. The paper outlines the objectives and approach of the research study. Sixty meters of core have been collected and the initial laboratory phase of the research has recently begun.