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On Evaluating Characteristics of the Solute Transport in the Arid Vadose Zone
Author(s) -
Yu Zhongbo,
Dong Weiquan,
Young Michael H.,
Li Yiping,
Yang Tao
Publication year - 2013
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/gwat.12026
Subject(s) - vadose zone , soil water , infiltrometer , water potential , saturation (graph theory) , soil science , water flow , tracer , infiltration (hvac) , hydrology (agriculture) , chemistry , environmental science , hydraulic conductivity , geology , materials science , geotechnical engineering , physics , mathematics , combinatorics , nuclear physics , composite material
Abstract The transport of bromide (Br) under matric heads of 0, −2, −5, and −10 cm using undisturbed soil columns was investigated for understanding the solute transport in arid soils. Undisturbed soil cores were collected at ground surface, directly below where tension infiltrometer measurements were made in the Amargosa Desert, Nevada, United States. Laboratory experiments were conducted by introducing water containing Br tracer into a soil column maintained at steady‐state conditions. The observed data of breakthrough curves ( BTC ) were well fitted to an one‐region model, except for the cores at saturation, and a core at the matric head of −5 cm, from which the observed data were better fitted to a two‐region model. Fitted pore water velocities with the one‐region model ranged from 1.2 to 56.6 cm/h, and fitted dispersion coefficients ( D ) ranged from 2.2 to 100 cm 2 /h. Results for the core analyzed with the two‐region model indicated that D ranged from 27.6 to 70.9 cm 2 /h at saturation, and 25.7 cm 2 /h at the matric head of −5 cm; fraction of mobile water ( β ) ranged from 0.18 to 0.65, and mass transfer coefficient ( ω ) ranged from 0.006 to 0.03. In summary, the water fluxes and Br dispersion coefficients at investigated matric heads were very high due to the coarseness of the soils and possibly due to preferential flow pathways. These high water fluxes and Br dispersion coefficients would lead to a higher risk of deeper leaching accumulating nitrate nitrogen to the groundwater, and have significant effects on the desert ecosystem.