Calculate the retardation factor for tetrachloroethene (PCE*) in a silty clayey loam soil, using data from Table 5.5. Soil density is 2.5 g/[latex]cm^{3}[/latex] and effective porosity is 31%. [latex]^*[/latex] Other word substitutes for tetrachloroethene are: tetrachloroethylene and PERC.

For tetrachloroethene, [latex]K_{oc} = 155[/latex] Since no measured value for [latex]f_{oc}[/latex] is available, a value from Table 5.4 can be used. For a silty clayey loam soil, [latex]f_{oc}\approx 0.03[/latex]. [latex]K_{d} = 155\times 0.03 = 4.7[/latex] and [latex]R = 1 + \frac{2.5\times 4.7}{0.31} = 38[/latex] Tetrachloroethene has a [latex]K_{oc} = 155[/latex] nearly 10 times that of 1,2-DCA, which means that it is much less water-soluble. Thus, it is less mobile and has a higher retardation factor.

Question 5.14: Calculate the retardation factor for tetrachloroethene (PCE*......

Applications of Environmental Aquatic Chemistry A Practical Guide [1103138]

Calculate the retardation factor for tetrachloroethene (PCE*) in a silty clayey loam soil, using data from Table 5.5. Soil density is 2.5 g/ $cm^{3}$ and effective porosity is 31%.

$^*$ Other word substitutes for tetrachloroethene are: tetrachloroethylene and PERC.

TABLE 5.5 Chemical Properties Used for Calculating Partition Coefficients and Retardation Factors
CAS No.	Compound	$Chemical Group^{a}$	S Solubility of Pure Compound (mg/L)	HLC Henry’s Law Constant (atm · $m^{3}$ /L)	H Henry’s Law Constant (unitless)	$log K_{ow}$	$log K_{oc}$	$K_{oc}$ Organic Carbon Partition Coefficient (L/kg)	$T_{bp}$ Normal Boiling Point (°C)	$T_{mp}$ Normal Melting $Point^{b}$ (°C)
83-32-9	Acenaphthene	1	4.24E+00	1.55E-04	6.36E-03	3.92	3.85	7.08E+03	288	93
120-12-7	Anthracene	1	4.34E-02	6.50E-05	2.67E-03	4.55	4.47	2.95E+04	324	215
71-43-2	Benzene	2	1.75E+03	5.55E-03	2.28E-01	2.13	1.77	5.89E+01	178	5.5
56-55-3	Benzo(a)anthracene	1	9.40E-03	3.35E-06	1.37E-04	5.70	5.60	3.98E+05	376	84
205-99-2	Benzo(b)fluoranthene	1	1.50E-03	1.11E-04	4.55E-03	6.20	6.09	1.23E+06	380	168
207-08-9	Benzo(k)fluoranthene	1	8.00E-04	8.29E-07	3.40E-05	6.20	6.09	1.23E+06	401	217
50-32-8	Benzo(a)pyrene	1	1.62E-03	1.13E-06	4.63E-05	6.11	6.01	1.02E+06	380	176
117-81-7	Bis(2-ethylhexyl)phthalate	1	3.40E-01	1.02E-07	4.81E-06	7.30	7.18	1.51E+07	347	-55
56-23-5	Carbon tetrachloride	2	7.93E+02	3.04E-02	1.25E+00	2.73	2.24	1.74E+02	177	-23
57-74-9	Chlordane	2	5.60E-02	4.86E-05	1.99E-03	6.32	5.08	1.20E+05	329	106
108-90-7	Chlorobenzene	2	4.72E+02	3.70E-03	1.52E-01	2.86	2.34	2.19E+02	207	-45
67-66-3	Chloroform (Trichloromethane)	2	7.92E+03	3.67E-03	1.50E-01	1.92	1.60	3.98E+01	168	-64
218-01-9	Chrysene	1	1.60E-03	9.46E-05	3.88E-03	5.70	5.60	3.98E+05	379	285
50-29-3	DDT	1	2.50E-02	8.10E-06	3.32E-04	6.53	6.42	2.63E+06	278	109
53-70-3	Dibenzo(a,h)anthracene	1	2.49E-03	1.47E-08	6.03E-07	6.69	6.58	3.80E+06	295	269
84-74-2	Di-n-butylphthalate	1	1.12E+01	9.38E-10	3.85E-08	4.61	4.53	3.39E+04	323	-35
95-50-1	1,2-Dichlorobenzene	2	1.56E+02	1.90E-03	7.79E-02	3.43	2.79	6.17E+02	234	-17
106-46-7	1,4-Dichlorobenzene	2	7.38E+01	2.43E-03	9.96E+02	3.42	2.79	6.17E+02	231	53
75-34-3	1,1-Dichloroethane (1,1-DCA)	2	5.06E+03	5.62E-03	2.30E-01	1.79	1.50	3.16E+01	166	-97
107-06-2	1,2-Dichloroethane (1,2-DCA)	2	8.52E+03	9.79E-04	4.01E-02	1.47	1.24	1.74E+01	181	-36
75-35-4	1,1-Dichloroethlyene	2	2.25E+03	2.61E-02	1.07E+00	2.13	1.77	5.89E+01	152	-123
156-59-2	cis-1,2-Dichloroethlyene	2	3.50E+03	4.08E-03	1.67E-01	1.86	1.55	3.55E+01	168	-80
156-60-5	trans-1,2-Dichloroethlyene (DCE)	2	6.30E+03	9.38E-03	3.85E-01	2.07	1.72	5.25E+01	161	-50
78-87-5	1,2-Dichloropropane	2	2.80E-03	2.80E-03	1.15E-01	1.97	1.64	4.37E+01	187	-70
60-57-1	Dieldrin	2	1.95E-01	1.51E-05	6.19E-04	5.37	4.33	2.14E+04	323	176
121-14-2	2,4-Dinitrotoluene	1	2.70E+02	9.26E-08	3.80E-06	2.01	1.98	9.55E+01	310	71
115-29-7	Endosulfan	2	5.10E-01	1.12E-05	4.59E-04	4.10	3.33	2.14E+03	357	106
72-20-8	Endrin	2	2.50E-01	7.52E-06	3.08E-04	5.06	4.09	1.23E+04	381	200
100-41-4	Ethylbenzene	2	1.69E+02	7.88E-03	3.23E-01	3.14	2.56	3.63E+02	209	-95
206-44-0	Fluoranthene	1	2.06E-01	1.61E-05	6.60E-04	5.12	5.03	1.07E+05	347	108
86-73-7	Fluorene	1	1.98E+00	6.36E-05	2.61E-03	4.21	4.14	1.38E+04	299	115
76-44-8	Heptachlor	1	1.80E-01	1.09E-03	4.47E-02	6.26	6.15	1.41E+06	318	96
58-89-9	$\gamma$ -HCH (Lindane)	2	6.80E+00	1.40E-05	5.74E-04	3.73	3.03	1.07E+03	314	113
193-39-5	Indeno(1,2,3-cd)pyrene	1	2.20E-05	1.60E-06	6.56E-05	6.65	6.54	3.47E+06	432	162
74-83-9	Methyl bromide	2	1.52E+04	6.24E-03	2.56E-01	1.19	1.02	1.05E+01	136	-94
75-09-2	Methylene chloride	2	1.30E+04	2.19E-03	8.98E-02	1.25	1.07	1.17E+01	156	-96
91-20-3	Naphthalene	1	3.10E+01	4.83E-04	1.98E-02	3.36	3.30	2.00E+03	255	80
108-95-2	Phenol	1	8.28E+04	3.97E-07	1.63E-05	1.48	1.46	2.88E+01	235	41
129-00-0	Pyrene	1	1.35E-01	1.10E-05	4.51E-04	5.11	5.02	1.05E+05	353	151
100-42-5	Styrene	1	3.10E+02	2.75E-03	1.13E-01	2.94	2.89	7.76E+02	215	-33
79-34-5	1,1,2,2-Tetrachloroethane (PCA)	2	2.97E+03	3.45E-04	1.41E-02	2.39	1.97	9.33E+01	215	-44
127-18-4	Tetrachloroethylene (PCE, PERC)	2	2.00E+02	1.84E-02	7.54E-01	2.67	2.19	1.55E+02	201	-22
108-88-3	Toluene	2	5.26E+02	6.64E-03	2.72E-01	2.75	2.26	1.82E+02	195	-95
8001-35-2	Toxaphene	1	7.40E-01	6.00E-06	2.46E-04	5.50	5.41	2.57E+05	347	65 to 90
120-82-1	1,2,4-Trichlorobenzene	2	3.00E+02	1.42E-03	5.82E-02	4.01	3.25	1.78E+03	252	17
71-55-6	1,1,1-Trichloroethane (1,1,1-TCA)	2	1.33E+03	1.72E-02	7.05E-01	2.48	2.04	1.10E+02	175	-30
79-00-5	1,1,2-Trichloroethane (1,1,2-TCA)	2	4.42E+03	9.13E-04	3.74E-02	2.05	1.70	5.01E+01	197	-37
79-01-6	Trichloroethylene (TCE)	2	1.10E+03	1.03E-02	4.22E-01	2.71	2.22	1.66E+02	183	-85
67-66-3	Trichloromethane (chloroform)	2	7.92E+03	3.67E-03	1.50E-01	1.92	1.60	3.98E+01	168	-64
75-01-4	Vinyl chloride	2	2.76E+03	2.70E-02	1.11E+00	1.50	1.27	1.86E+01	126	-154
108-38-3	m-Xylene	2	1.61E+02	7.34E-03	3.01E-01	3.20	2.61	4.07E+02	211	-48
95-47-6	o-Xylene	2	1.78E+02	5.19E-03	2.13E-01	3.13	2.56	3.63E+02	214	-25
106-42-3	p-Xylene	2	1.85E+02	7.66E-03	3.14E-01	3.17	2.59	3.89E+02	211	13
Source: Adapted from USEPA, 1996, Soil Screening Guidance: Technical Background Document, Office of Emergency and Remedial Response, Washington, DC, EPA/540/R95/128.
$^a$ Group 1: Semivolatile nonionizing organic compounds. Fitted to $log K_{oc} = 0.983 log K_{ow} + 0.00028$ . Group 2: Volatile organic compounds, chlorobenzenes, and certain chlorinated pesticides. Fitted to $log K_{oc} = 0.7919 log K_{ow} + 0.0784$ .
$^b$ Compounds solid at soil temperature are defined as those with a melting point >20°C. Compounds liquid at soil temperature are defined as those with a melting point <20°C

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For tetrachloroethene, $K_{oc} = 155$
Since no measured value for $f_{oc}$ is available, a value from Table 5.4 can be used. For a silty clayey loam soil, $f_{oc}\approx 0.03$ .
$K_{d} = 155\times 0.03 = 4.7$ and $R = 1 + \frac{2.5\times 4.7}{0.31} = 38$
Tetrachloroethene has a $K_{oc} = 155$ nearly 10 times that of 1,2-DCA, which means that it is much less water-soluble. Thus, it is less mobile and has a higher retardation factor.

TABLE 5.4 Typical Values of Fraction of Organic Carbon in Different Soils
Type of Soil		Typical $f_{oc}$ (wt. fraction)
Coarse soil		0.04
Silty loam		0.05
Silty clayey loam		0.03
Clayey silty loam		0.005
Clayey loam		0.004
Sand		0.0005
Glaciofluvial		0.0001
Note: These typical values were collected from many sources. They should only be used as crude estimates when site-specific measurements cannot be obtained. The range of measured values for a single soil type can span a factor of 100.