Interfacial partitioning tracer test measurements of organic-liquid/water interfacial areas: Application to soils and the influence of surface roughness

Interfacial areas between an organic immiscible liquid and water were measured for two natural soils using the aqueous-phase interfacial partitioning tracer test method. The measured values were compared to measured values for silica sands compiled from the literature. The data were compared using the maximum specific interfacial area as a system index, which is useful for cases wherein fluid saturations differ. The maximum specific interfacial areas measured for the soils were significantly larger than the values obtained for the sands. The disparity between the values was attributed to the impact of surface roughness on solid surface area and hence film-associated interfacial area. A good correlation was observed between maximum specific interfacial area and specific solid surface area measured with the N₂/BET method. The correlation may serve as a means by which to estimate maximum specific organic-liquid/water interfacial areas. Interfacial areas measured with the interfacial partitioning tracer method were compared to interfacial areas measured with high-resolution microtomography. Values measured with the former method were consistently larger than those measured with the latter, consistent with the general inability of the microtomography method to characterize roughness-associated surface area.