Fig. 2. Tracer breakthrough curves from tile drain under a 2.4 mm h^–1 steady-state irrigation rate. The o-TFMBA (o-trifluoromethylbenzoic acid) experiment was conducted in autumn 2001, while the PFBA (pentafluorobenzoic acid) experiment was conducted in spring 2002. Calculated curves are best fit of Eq. [5] to data.