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iffigation. Their solutions can be used to evaluate the impact of rainfall on subsurface FIGURE G-1
<br /> moisture conditions. The drainage of soil by gravity following infiltration of one
<br /> centimeter of water for two soil types,sand and silt,is shown in Figure 1. The figure aen o..u,.a•curv.9(asm. ,at al..1970)
<br /> demonstrates that these two sail types drain within approximately five days.
<br /> Additionally,Sisson et al.(1980)derived a one-dimensional unsaturated Flow equation
<br /> by assuming a unit gradient approximation. The estimation of the rale of drainage for a
<br /> silty sand is shown in Figure 2. The figure shows that silty sand drains within about five F o.
<br /> days,agreeing with the approximations by Gardner et al.(1970).
<br /> REFERENCES 25 c,�T .yy. 1a°`,`"'�,�
<br /> • yp y
<br /> Auer, L.H.,N.D.Rosenberg,K.H.Birdsall,and E.M.Whitney. 1986. The Effects of
<br /> Barometric Pumping on Contaminant Transport. Journal of Contaminant Hydrology,v. f.
<br /> 24,p.145-166. 'ANO
<br /> Clements,W.E.,and M.Wilkening. 1974. Atmospheric.Pressure Effects on 222Rn ° ° Tim*I°•w°l
<br /> Transport across the Earth-Air Interface. Journal of Geophysical Research,v.79,n.33,
<br /> p.5025-5029.
<br /> Eberling,B.,F.Larsen, S.Christensen,and D. Postma. 1998. Gas Transport in a Soil drainage curves where gravity predominates as derived from Gardner at al.(1970).
<br /> Confined Unsaturated Zone during Atmospheric Pressure Cycles. Water Resources The figure denotes two scenarios,sill and sand,where the initial unsaturated hydraulic
<br /> Research,v.34,p.2855-2862. conductivity within the infiltration zone is 1 centimeter per day and 1000 centimeters per
<br /> day,respectively. An instantaneous infiltration of one centimeter is assumed in the
<br /> Gardner,W.R.,D.Hlllel,and Y.Benyamini. 1970. Post-Irrigation of Soil Water,1. evaluation. The figure demonstrates that drainage to asymptotic moisture conditions
<br /> occurs within about five days for these two soil types.
<br /> Redistribution. Water Resources Research,v.6,n.3,p.851 –861.
<br /> Kienbusch,M.,and D.Rancor. 1986, Validation of Flux Chamber Emission FIGURE G-2
<br /> Measurements on a Soil Surface. Draft Report to EPA-EMSL,Las Vegas,under EPA —-
<br /> Contract No.68-02-3889,Work Assignment 69,June 1986. s°n Dirainaga C0a°°law°„u m..19w)
<br /> Nilson,R.H., E.W. Peterson,K.H.Lie,N.R. Burkhard,and J.R.Hearst. 1991.
<br /> Atmospheric Pumping:A Mechanism Causing Vertical Transport of Contaminated
<br /> Gases through Fractured Permeable Media. Journal of Geophysical Research,v. B13,
<br /> p 21,933-21.948,
<br /> f n moo.°
<br /> e, S
<br /> Massmann,J,and D.F.Farrier. 1992. Effects of Atmospheric Pressures on Gas ,w °
<br /> Transport in the Vadose Zone. Water Resources Research,v.28,n.3,p.777-791.
<br /> Radian Corporation. 1984. Soil Gas Sampling Techniques of Chemicals for Exposure
<br /> Assessment–Data Volume. Report to EPA-EMSL,Las Vegas under EPA Contract No. ow ow .° ow
<br /> 68-02-3513,Work Assignment 32,March 1984.
<br /> Sisson,J. B.,A.H.Ferguson,and T.Th.van Genuchten. Simple Method for Predicting
<br /> Drainage from Field Plots. Soil Science Society of America Journal,v.44,p.1147– Soil drainage curves as derived from Sisson at al.(1980)where a unit gradient is
<br /> 1152• assumed. The figure denotes one scenario,silty sand,where the initial unsaturated
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