Comparison of the stable-isotopic composition of soil water collected fromsuction lysimeters, wick samplers, and cores in a sandy unsaturated zone

Soil water collected from suction lysimeters and wick samplers buried in th e unsaturated zone of a sand and gravel aquifer and extracted from soil cor es were analyzed for stable oxygen and hydrogen isotope values. Soil water isotopic values differed among the three sampling methods in most cases. Ho wever, because each sampling method collected different fractions of the to tal soil-water reservoir, the isotopic differences indicated that the soil water at a given depth and time was isotopically heterogeneous. This hetero geneity reflects the presence of relatively more and less mobile components of soil water. Isotopic results from three field tests indicated that 95-1 00% of the water collected from wick samplers was mobile soil water while s amples from suction lysimeters and cores were mixtures of more and less mob ile soil water. Suction lysimeter samples contained a higher proportion of more mobile water (15-95%) than samples from cores (5-80%) at the same dept h. The results of this study indicate that, during infiltration events, soi l water collected with wick samplers is more representative of the mobile s oil water that is likely to recharge ground water during or soon after the event than soil water from suction lysimeters or cores. Published by Elsevi er Science B.V.