# EPA On-line Tools for Site Assessment Calculation

**Transport from a Continuing or Pulse Concentration Source**

**One Dimensional Transport From a Pulse Source**

R = retardation factor []

D = dispersion constant [L2/T]

v = seepage velocity [L/T]

μ = first order decay constant [1/T]

**with the initial and boundary conditions**

**retardation factor**

R = 1 + ρ
_{b}
k_{d} /θ

R = retardation factor

ρ
_{b}
= bulk density = ρ
_{s}
(1-θ)

ρ
_{s}
= solids density

θ = porosity

k
_{d}
= (soil) distribution coefficient = f
_{oc}
K
_{oc}

f
_{oc}
= fraction organic carbon

K
_{oc}
= organic carbon/water partition coefficient

**travel time** t
_{tr}
= x R /v

t
_{tr}
= advective travel time
^{*}

v = seepage velocity

R = retardation factor

x = distance

^{*}
assuming one-dimensional, steady flow, constant gradient

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