117-2 Modeling Pore-Size Spectrum In Soil and Sand Columns by Breakthrough Curves of Chloride.



Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

ABSTRACT WITHDRAWN

The objective of this study was to develop a novel methodology to use BTC of non-conservative tracers such as chloride and bromide as surrogates for the purpose of calculating pore-water velocity and corresponding pore-size spectrums in soils. Miscible displacement tests of Cl were conducted on repacked sand and undisturbed soil columns with 8.0 cm id and 13-30 cm length.  The resultant BTCs were divided into about 30 segments, and amount of mobile water (Qmi) needed to transport the amount of tracer recovered at the exit of the column for corresponding segment was calculated as Qmi = (DCrixDPrixP0)xPr(Cr=1.0), where DCri is the difference in dimensionless concentration, DPri is the difference in dimensionless pore volume, P0 is the amount of water held in the column (simply pore volume of the column), and Pr(Cr=1.0) is dimensionless pore volume at Cr =1.0.  Pore water velocity (vi) for segment i was calculated as vi = (zl/t) where,  z is tourtuousity (-), l (L) is the length of the column and t (T) is time elapsed from traced effluent to start displacing non-traced effluent in the column. Mean radius of the pores within size class i was calculated, using calculated vi with Poiseuille’s equation.  Number of the pores in each size-class i was calculated dividing volume of effluent discharging in unit time (Qmi/(ti+1-ti), where ti+1-ti is the time length for which  Qmi is recovered) by cross-sectional area of mean pore-size calculated for size class i. The predicted mean pore-water velocity (vp) for saturated columns was calculated form geometric mean of pore-water velocity-values calculated for all the segments. Saturated mean pore-water velocity of the columns was measured, and measured (vm) and predicted (vp) pore-water velocity-values were converted to saturated hydraulic conductivity, multiplying vm and vp by saturated water content (L3 L-3) of the columns.  Correlation analysis conducted between vm and vp resulted in a correlation coefficient of r= 0.90.
See more from this Division: S01 Soil Physics
See more from this Session: General Soil Physics: II (Includes Graduate Student Competition)