Tracer Characteristics of Brilliant Blue FCF and FD&C Green No. 3 in Arid Soils.

Dyes are important tracers for studying water flow and solute transport in the vadose zone. Brilliant Blue FCF (C.I. 42090) is one of the most often used dye tracers for visualization of water flow paths in soils. However, some investigators have suggested that Brilliant Blue FCF is strongly sorbed to calcareous soils and thus it is not suitable for use as a tracer in such soil environments. FD&C Green No. 3 (C.I. 42053) has a similar chemical structure to Brilliant Blue FCF, differing in that it contains an additional hydroxyl group. In a previous study using a sandy soil of pH 8, FD&C Green No. 3 showed less sorption than Brilliant Blue FCF. Therefore, in terms of mobility, FD&C Green No. 3 appears to be a better tracer compared to Brilliant Blue FCF. However, tracer characteristics of FD&C Green No. 3 have not been systematically studied. The objective of this study is to evaluate sorption and transport characteristics of the two dyes in calcareous arid soils.