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Solute Transport under Transient Flow Conditions Estimated Using Time Domain Reflectometry
Author(s) -
Risler P. D.,
Wraith J. M.,
Gaber H. M.
Publication year - 1996
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/sssaj1996.03615995006000050003x
Subject(s) - reflectometry , soil water , soil science , effluent , dispersion (optics) , time domain , electrical resistivity and conductivity , chemistry , hydraulic conductivity , environmental science , environmental engineering , physics , electrical engineering , computer science , optics , computer vision , engineering
Improved methods having high resolution in space and time are needed to monitor transport of soluble chemicals in soils. We used time domain reflectometry (TDR) to measure breakthrough curves (BTCs) for Br − during miscible displacement in repacked soil columns under nonsteady water flow conditions. A simple linear model was used to estimate soil solution electrical conductivity (σ w ) based on TDR‐measured bulk soil electrical conductivity (σ a ) and volumetric water content (θ). An efficient calibration method was developed whereby required model parameters were estimated in the same soil volume and under the same flow conditions as were used in subsequent transport experiments. Breakthrough curves measured using TDR were similar to those based on electrical conductivity or Br − concentration in effluent fractions, although peak σ w were substantially lower for TDR than for effluent from two of the four soils. Effluent σ w BTCs were adequately predicted based on TDR σ a and θ for all four soils when parameters of the simple linear model or two alternative models were optimized to the effluent data. Time moments and convection‐dispersion equation (CDE) transport parameters based on time moments of measured BTCs were similar for TDR and effluent analyses. Our results indicate that TDR has potential to monitor the status of representative concentrations of ionic solutes under laboratory and field conditions, without the need to impose steady water flow.