Simplified behaviors from increased heterogeneity: II. 3-D Uranium transport at the decimeter scale and intertank comparisons

Upscaling from bench scale systems to field scale systems incorporates physical and chemical heterogeneities from atomistic up to field scales. Heterogeneities of intermediate scale (~ 10− 1 m) are impossible to incorporate in a bench scale experiment. To transcend these scale discrepancies, this second in a pair of papers presents results from an intermediate scale, 3-D tank experiment completed using five different particle sizes of uranium contaminated sediment from a former uranium mill field site. The external dimensions of the tank were 2.44 m × 0.61 m × 0.61 m (L × H × W). The five particle sizes were packed in a heterogeneous manner using roughly 11 cm cubes. Small groundwater wells were installed for spatial characterization of chemical gradients and flow parameters. An approximately six month long bromide tracer test was used for flow field characterization. Within the flow domain, local uranium breakthrough curves exhibited a wide range of behaviors. However, the global effluent breakthrough curve was smooth, and not unlike breakthrough curves observed in column scale experiments. This paper concludes with an inter-tank comparison of all three experimental systems presented in this pair of papers. Although there is a wide range of chemical and physical variability between the three tanks, major chemical constituent behaviors are often quite similar or even identical.

► A 3-D uranium transport experiment at a unique scale (~ 2 m) was completed.
► The tank was heterogeneously packed with 5 different particle sizes of sediment.
► Local uranium behavior was heterogeneous; effluent behavior was homogenized.
► We compare tank data from 3 tanks with different levels of heterogeneity.
► Despite tank differences, chemical relationships between constituents are similar.