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Heterogeneous Flow and Solute Transport in an Unsaturated Stony Soil Monolith
Author(s) -
Buchter B.,
Hinz C.,
Flury M.,
Flühler H.
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900010002x
Subject(s) - subsoil , porous medium , soil water , monolith , soil science , macropore , breakthrough curve , hydrology (agriculture) , outflow , dispersion (optics) , water flow , chemistry , geology , mineralogy , porosity , geotechnical engineering , physics , mesoporous material , biochemistry , oceanography , optics , catalysis , organic chemistry , adsorption
Field studies of solute transport have shown that water flow velocity may vary tremendously across a field. To assess the effects of flow heterogeneity on solute transport in a stony subsoil, miscible displacement experiments were conducted in a large undisturbed gravel monolith (75‐cm length, 30‐cm diam.). The soil sample contained about 0.8 kg kg −1 of gravel. Two consecutive pulses (runs) of a Cl − solution were leached through the monolith, each at matric pressures ranging from −2.0 to −2.2 kPa. The cumulated outflows, collected with 19 separate porous plates located at the bottom, ranged from 0 to 3000 mL. The outflow rates of the individual plates were constant and highly correlated between the two runs ( r = 0.95). The Cl − breakthrough curves (BTCs) of the total and individual BTCs could be well described by the classical convective‐dispersive equation. Pore water velocities, dispersion coefficients, and dispersivities of the two runs indicated a high correlation of the breakthrough behavior of the individual outlets ( r = 0.995, 0.88, and 0.97, respectively). In addition, the iodine starch method revealed a heterogeneous flow pattern. Even though the column was resaturated and drained between the two runs, the results between the two consecutive runs were consistent. This suggests that the flow paths of water remained invariant and might be an intrinsic feature of a soil medium for a given water content.