Appendices Appendix A. Screening model for assessing the leaching potential of volatile solutes The governing equations for transport of volatile chemicals in the dual-porosity model can be expressed as (Hantush et al., 2002): (A.1) for mobile region, for immobile region, (A.2) where and are the solute concentration [M/L3], retardation factor ( and ) [‒], and decay C, R, k constant (km=ln(2)/T1/2, m and im) [T-1], respectively. The subscripts indicate kim=ln(2)/ T1/2, mobile (m) and immobile (im) regions. Independent variables are the time [T] and the vertical t coordinate [L]. Here, and represent the soil bulk density [M/L3], distribution z Kd, Kh ρb, coefficient [L3/M], and dimensionless Henry’s constant [‒], respectively. And and f, T1/2 κ*, θ*, signify the fraction of soil [‒], volumetric air content [‒], volumetric water content [‒], and chemical half-lives [T] in two regions, respectively. The and indicate the mean pore water u µ velocity (u=q/θm, where is the water flux through a unit area perpendicular to the direction of q water flow) [L/T] and the uptake by plant roots (µ=ku/(kmθmRm), where is the first-order ku uptake rate constant) [T-1], respectively. The represents the mass transfer rate (, where and b α
Appendices Appendix A. Screening model for assessing the leaching potential of volatile solutes The governing equations for transport of volatile chemicals in the dual-porosity model can be expressed as (Hantush et al., 2002): (A.1) for mobile region, for immobile region, (A.2) where C, R, and k are the solute concentration [M/L3], retardation factor ( and ) [‒], and decay constant (km=ln(2)/T1/2, m and kim=ln(2)/ T1/2, im) [T-1], respectively. The subscripts indicate mobile (m) and immobile (im) regions. Independent variables are the time t [T] and the vertical coordinate z [L]. Here, ρb, Kd, and Kh represent the soil bulk density [M/L3], distribution coefficient [L3/M], and dimensionless Henry’s constant [‒], respectively. And f, κ*, θ*, and T1/2 signify the fraction of soil [‒], volumetric air content [‒], volumetric water content [‒], and chemical half-lives [T] in two regions, respectively. The u and µ indicate the mean pore water velocity (u=q/θm, where q is the water flux through a unit area perpendicular to the direction of water flow) [L/T] and the uptake by plant roots (µ=ku/(kmθmRm), where ku is the first-order uptake rate constant) [T-1], respectively. The α represents the mass transfer rate (, where and b
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