Page 177 - Materials Chemistry, Second Edition

160 Practical Design Calculations for Groundwater and Soil Remediation

This value, 4,405 mg/kg, represents the maximum 1,1-DCA con-
centration in the soil if the free-product phase of 1,1-DCA is
absent.
(c) Since the calculated DCA concentration, 4,405 mg/kg, is less
than the reported concentrations of the soil samples, the free-
product phase of 1,1-DCA should be present in the subsurface.

Discussion:
Estimated values of the saturated soil concentration from Example 5.3
and Example 5.4 are essentially the same.

To determine the extracted soil vapor concentration in the absence of free
product in the subsurface, the following procedures can be used:

Step 1: Obtain the physicochemical data of the COC (e.g., from Table 2.5).
Step 2: Determine the K value using Equation (2.28) and K value
oc
p
using Equation (2.26).
Step 3: Determine the vapor concentration by using Equation (2.40) and
the COC concentration in soil.

Information needed for this calculation:

• COC concentration of soil samples
• Henry’s constant of the COC
• Organic–water partition coefficient, K ow
• Organic content, f oc
• Porosity, ϕ
• Degree of water saturation
• Dry bulk density of soil, ρ b
• Total bulk density of soil, ρ t

Example 5.5: Estimate the Extracted Vapor Concentration
(in the Absence of the Free Product)
A subsurface is impacted by a benzene spill. The average benzene concentra-
tion of the soil samples, taken from the impacted zone, is 500 mg/kg. The
subsurface has the following characteristics:

• Porosity = 0.35
• Organic content = 0.03
• Degree of water saturation = 45%