Table 1. Soil characteristics.
tent with that described in the Draft Statement of
Work for Quick Turnaround Analysis (U.S. EPA 1993),
Soil
% organic
while the Aq-NaCl sat'd-HS (salting-out) method
Description
Abbreviation
type
carbon*
was recommended in the initial draft of Method
Ottawa sand
Ott
>99% sand
0.035
5021 (U.S. EPA 1986).
Ft. Edwards
Ft. E
>90% clay
0.5
For each comparison, all of the samples were
CRREL
CR-A
silty/sand
1.5
handled in a manner that prevented volatization
Pt. Barrow, Alaska
Pt. B
silty/clay
7.1
losses prior to and during headspacegas chroma-
CRREL
CR-B
silty/sand
0.90
tography (HS/GC) analysis. In addition, many of
* Leco CR-12 furnace analysis (Merry and Spouncer 1988).
the samples extracted with a solvent were ana-
lyzed over time to assess extraction kinetics and
long term analyte concentration stability. The pre-
pared laboratory samples included five soils of
Table 2. Octanolwater partition coefficients and
various organic carbon and clay contents, spiked
boiling points of analytes.
with benzene (Ben), toluene (Tol), ethylbenzene
Boiling
(E-Ben), p-xylene (p-Xyl), o-xylene (o-Xyl), trans-
Log of octanolwater point
1,2-dichloroethene (TDCE), cis-1,2-dichloroethene
(C)
Compound (abbreviation)
partition coefficient
(CDCE), trichloroethene (TCE) and tetrachloroet-
trans-1,2-dichloroethene (TDCE)
2.09
47.2
hene (PCE). Two laboratory-spiking methods were
cis-1,2-dichloroethene (CDCE)
--
55.0
used--an aqueous treatment with a 2-day sample
benzene (Ben)
2.13
80.1
equilibration, and vapor fortification with a 4- to
trichloroethene (TCE)
2.53
87.2
6-week sample equilibration. Longer analyte
tetrachloroethene (PCE)
2.60
121.0
matrix equilibration periods were not used with
toluene (Tol)
2.65
110.6
o-xylene (o-Xyl)
2.95
144.0
the aqueous spiking method, since under these
ethylbenzene (E-Ben)
3.13
136.2
conditions biodegradation of aromatic compounds
p-xylene (p-Xyl)
3.18
138.4
is likely (Hewitt 1995a,b; Hewitt 1997).
EXPERIMENTAL METHODS
Table 3. Experimental designs: soil types, sample
replicates, and methods of sample preparation for
Two laboratory sample spiking procedures, six
analysis.
sample preparation methods, and one analysis
method are described below. Characteristics of the
No. of rep. Soil types
Methods of sample preparation*
various soil matrices studied and the octanolwa-
I. Aqueous spike
ter partition coefficients and boiling points of the
15
Ott
a. Heated HS
analytes are presented in Tables 1 and 2 respec-
15
Ft. E
b. Aqueous solution acidified with
tively.
15
CR-A
NaHSO4
15
Pt. B
c. Aqueous solution NaCl-saturated
and acidified with H3PO4
Soil subsample preparation
d. MeOH extraction
e. Tetraglyme extraction
Aqueous treatment--experiment I
An aqueous spiking solution was prepared by
II. Vapor fortification treatment
adding microliter volumes (3.15.8 L) of reagent
6
Ott
a. MeOH extraction
6
Ft. E
b. Tetraglyme extraction
grade Ben, Tol, E-Ben, p-Xyl, o-Xyl, TDCE, CDCE,
6
CR-A
TCE, and PCE to a 100-mL volumetric flask con-
6
Pt. B
taining about 103 mL of groundwater. Once all the
III. Vapor fortification treatment
analytes had been transferred using a microliter
18
CR-B
a. Heated HS
syringe (Hamilton), the solution was mixed for 48
b. Aqueous solution acidified with
NaHSO4
hours with a stirring bar. The target concentration
c. Aqueous solution NaCl saturated
of each analyte was 50 mg/L; however, there were
and acidified with H3PO4
some volatilization losses.
d. MeOH extraction
Four different air-dried soils were spiked with
e. Tetraglyme extraction
this aqueous solution (Table 3). Fifteen 2.00 0.01-
f. PPG extraction
g subsamples of each soil type were transferred to
* Triplicates of a soil type were used for each method of sam-
ple preparation.
1-mL glass ampoules using a funnel and spatula.
2
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