Artifacts caused by collection of soil solution with passive capillary samplers

Soil solution was collected with passive capillary samplers (PCAPS) and zero-tension samplers (ZTS) from A horizons of forested soils. The volume and chemistry of collected solutions were measured weekly during discrete seasonal collection periods. Acid-washed PCAPS increased alkalinity (3-fold), pH (1-3 units), and concentrations of Ca (2-fold), Na (8-fold), and Si (4-fold), relative to ZTS solutions. Aluminum concentrations were dramatically reduced in PCAPS compared with ZTS samples. Differences in solution chemistry were attributed to leaching and weathering of fiberglass wicking material utilized in the PCAPS. In addition, PCAPS collected greater volumes (normalized by sampler area) of solution relative to ZTS in weak-structured sandy loam soil due to a preponderance of matrix flow. The results indicate that the PCAPS used in this study are not suitable for aqueous geochemical studies of dilute soil solutions.