An accurate assessment of leaching losses in the vadose zone requires measurement of both solute and water flux to compute flux concentrations (C[subscript F]). Leachate collected at a depth of 1.2 m in 32 passive capillary samplers (PCAPS), which sample soil-pore water continuously at tensions of 0–50 cm H₂O was compared to that collected in 32 suction cup samplers operated under a falling head vacuum of 530-cm H₂O over a 2-year period. There was evidence that PCAPS collected CF and suction cup samplers collected resident concentrations (C[subscript R]) as shown by the earlier breakthrough of a bromide tracer in the PCAPS as compared to the suction cup samplers. C[subscript R] was up to 100% lower than C[subscript F] during the rising branch of Br tracer breakthrough and up to 78% greater during the declining branch of breakthrough. Br content and water flux into PCAPS were correlated with correlation coefficients changing from positive to negative values with the advancement of the tracer breakthrough peak through the profile indicating the declining importance of preferential flow on Br transport. C[subscript R] and C[subscript F] differed significantly (P < 0.05) for 35% of the sampling events for NO₃, but seasonal means were mostly insignificantly different for this regularly applied and therefore more uniformly distributed anion. The early breakthrough of Rhodamine WT and Brilliant Blue FCF, which was applied with the Br, was very low with 0.15% and 0.08% of the initial concentration C₀, respectively, with C[subscript R] differing from C[subscript F] by up to −100%. For all tracers, mass leached using C[subscript R] is therefore prone to bias for short-term (<0.6 pore volumes) monitoring.Keywords: Hydrology: Unsaturated zone, Hydrology: Groundwater quality, Hydrology: Groundwater hydrology, Hydrology: Instruments and technique
