Titre :
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In-situ evaluation of capillary wick tension in wick lysimeters for sampling from vadose zone
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Auteurs :
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M. Wang ;
OREGON STATE UNIVERSITY USA
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Type de document :
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thèse/mémoire
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Editeur :
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University of Oregon Press, 1994
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Format :
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58 p.
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Langues:
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= Anglais
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Catégories :
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HYDROLOGIE
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Mots-clés:
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CAPILLAIRE
;
SOL
;
EAU SUPERFICIELLE
;
MILIEU NON SATURE
;
ECHANTILLONNAGE STATISTIQUE
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Résumé :
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Passive capillary wick pan samplers (PCAPS), which apply suction to the soil via fiberglass wicks, have been shown to give superior results for long term mass balance of water and chemical loading in the vadose zone, when compared to zero tension pan samplers and suction cup samplers. In laboratory tests, the in-situ capillary suction of a fiberglass wick was observed at a variety of flow rates. Correlation between soil water potential and sampler flux was recorded to demonstrate the operational properties of capillary wick samplers under field conditions. Tensiometers were mounted in the top panel and along the length of the hanging wick to monitor the performance of the wick at different flow rates (0 to 2.0 mm/hr). Two critical design factors have been identified: The entrance edge from the top panel to the tubing containing the wick must be well rounded to prevent disturbance of the capillary wick potential, and the tubing diameter must be large (in this case 3.18 cm), so as to not physically constrain the diameter of the wick. It was demonstrated that the capillary potential of the wick was uniform across the top plate. In addition, one wick was found to be sufficient to sample a 28.2 X 31 cm area in silica grade 70 sand. The capillary potential in the hanging wick was shown to be responsive to sampler flux. Field testing of the PCAPS performance was conducted at the O.S.U. North Willamette Experiment Station in Northwest Oregon. Thirty-two tensiometers were installed to monitor the soil water potential at the depth of 16 wick samplers. The soil water potentials were monitored through the fall and winter of 1992. Soil water potentials were less negative than the capillary potential of PCAPS at the wick at low flow rates (0 to 0.3 mm/hr) which would suggest the PCAPS were not over-sampling this soil.
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Diplôme :
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Master of science, Oregon State University, USA
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