Environmental Engineering Reference
In-Depth Information
TABLE 10.9
CRF SOIL Values for Common DNAPL VOCs
LNAPL Compound
Soil Type
CRF SOIL
Tetrachloroethene (PCE)
Clay
3,955.0
Silty clay
647.0
Sand silty clay
591.0
Sand
371.0
Trichloroethene (TCE)
Clay
255.0
Silty clay
40.0
Sand silty clay
37.0
Sand
23.0
cis -1,2-Dichloroethene
Clay
3,698.0
Silty clay
1,205.0
Sand silty clay
1,159.0
Sand
993.0
trans -1,2-Dichloroethene
Clay
491.0
Silty clay
111.0
Sand silty clay
99.0
Sand
87.0
Vinyl chloride
Clay
5,727.0
Silty clay
2,575.0
Sand silty clay
2,508.0
Sand
2,308.0
1,1,1-Trichloroethane (1,1,1-TCA)
Clay
13.7
Silty clay
2.5
Sand silty clay
2.3
Sand
1.6
Mean DNAPL CRF SOIL for
degradation sequence from PCE
to vinyl chloride a (Figure 7.4)
Clay
2,825.0
Silty clay
915.6
Sand silty clay
878.8
Sand
756.4
a Represents cumulative risk.
Table 10.12 compares the CRF GW with the CRF SOIL .
From Table 10.12, it is clear that the contaminants exhibiting high soil risk factors (e.g.,
chlordane, mercury, and PCBs) have a low groundwater contaminant risk factor. This
behavior is primarily attributed to their low mobility. Computing the ratio of the data in
columns 3 and 4 yields the likelihood of a particular contaminant type contaminating soil
and/or groundwater. This computation is shown in column 5, and the values range from
1.0 × 10 −9 to 766—a difference in magnitude of more than a billion.
A ratio value of 1.0 in column 5 indicates a particular chemical compound has an equal
probability of contaminating soil and groundwater; values less than 1.0 indicate a higher
likelihood of contaminating soil only, and values greater than 1.0 mean the compound
is more likely to contaminate groundwater. The high mean (arithmetic average) CRF GW /
CRF SOIL ratios of chromium VI and DNAPL clearly suggest these compounds have the
 
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