&EPA
                             United States
                             Environmental Protection
                             Agency
                                     National Risk Management
                                     Research Laboratory
                                     Ada, OK 74820
                             Research and Development
                                     EPA/600/S-97/001   April 1997
ENVIRONMENTAL
RESEARCH   BRIEF
                         Characterization of Organic Matter in
                                  Soil  and Aquifer Solids

             M.J. Barcelona,3 M.E. Caughey,b R.V. Krishnamurthy,c D.M. Shaw,cand K. Maasc
Abstract
The focus of this work was the evaluation of analytical methods
to determine and characterize fractions of subsurface organic
matter. Major fractions of total organic carbon (TOC) include:
particulate organic carbon (POC) in aquifer material, dissolved
organic carbon (DOC) and both volatile (VOC) and non-volatile
(NVOC) organic carbon sub-fractions.

POC makes up the bulk of  TOC in  contaminated and
uncontaminated subsurface soils and aquifer materials. The
volatile subfraction of POC can be determined quantitatively
when minimally disturbed sub-cores are preserved immediately
in the field. Methanol and acid addition (i.e., HCI, NaHSO4) to pH
2 are adequate  preservatives for specific volatile organic
compound determinations. An interlaboratory round-robin test to
improve acidification and removal methods for carbonates in
total carbon using sulfurous acid (H2SO3) showed sensitivity to
several factors. Thesefactors include: operator care, acidstrength
and carbon content, and particularly, the incomplete removal of
inorganic carbon at high total carbon to organic carbon ratios.

Stable isotopic characteristics of NVOC from fuel contaminated
and organic-enriched  environments were found to be quite
sensitive to the stable isotopic  signatures of natural organic
matter. The extractability of POC by a range of high to medium
Department of Civil and Environmental Engineering, University of Michigan, Ann
Arbor, Ml 48109-2099.
'Office of Environmental Chemistry, Illinois State Water Survey, Champaign, IL
61820.
Departments of Geology and Chemistry, Western Michigan University,
Kalamazoo, Ml 49008.
                      polarity solvents resulted in the observations that relatively little
                      POC was extractable and water extracted comparable amounts
                      to 1:1 mixtures of 0.01M KOH in methanol:toluene.

                      Introduction
                      Organic matter in subsurface systems is a complex mixture of
                      natural organic substances, fossil fuels and a variety of synthetic
                      compounds. The transport and fate of organic contaminants is
                      quite dependent on the nature and distribution of organic carbon
                      in general.

                      Dispersion, sorption and degradation are processes which affect
                      organic compound  transport and  fate. The estimation of the
                      influence of these processes depends heavily on the quantitative
                      determination  of fractions of organic carbon in soils and aquifer
                      materials (Powell  et al., 1989).  Conventional contaminant
                      analytical methods  have focused on constituents in  fuels and
                      synthetic mixtures (e.g., solvents,  plasticizers and other
                      chemicals)  (Keith, 1991). Methods for determining volatile and
                      non-volatile organic carbon (i.e., VOC and NVOC) in  dissolved
                      (DOC) and  particulate (POC) fractions have seen relatively little
                      attention in the literature or practice of subsurface environmental
                      chemistry (Thurman, 1985).

                      Methods for the determination of major carbon subfractions, as
                      well  as the specific organic compounds of which  they are
                      composed, must be based on  quantitative preservation,
                      separation, and analytical methods which lend themselves to
                      routine practice. In this way, the  roles,  identity, and fates of
                      specific organic contaminants may be incorporated into process-
                      level hydrogeological investigations.

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The present study  was organized  around  the  analytical
determination of organic carbon fractions. Each fraction  was
related to the matrix  it was associated with given its volatility,
extractability/ polarity and its probable origin as identified by the
stable isotopic characteristics of the carbon.

This operational categorization  of total carbon is shown  in
Figure 1. Corresponding separation and  analytical methods  to
selected categories in Figure  1 are shown in Table 1.

The primary objectives of the study address aspects of Figure 1
and Table 1 which are central to the routine application of carbon
fractionation methods. These  objectives were:

1)  Refinement of the  acidification step  (i.e.,  TIC removal)
    techniques for  the quantitative determination of non-volatile
    organic carbon (NVOC ) in aquifer materials. Testing of the
    methodology in  an  interlaboratory round-robin trial.  This
    objective addresses problems associated with Category 1
    and 2 analyses.
2)  Evaluation of in-field preservation techniques for sub-cores
    of split-spoon or piston cores of subsurface materials coupled
    with methods to determine VOCpandNVOCp at the elemental
    and specific compound level. This objective  addresses
    issues involved in Category 3.
                                3)   Initial development of an  extractability procedure to
                                    characterize the leachability of various fractions of organic
                                    matter by varying polarity solvents as shown in Category 4.
                                and,

                                4)   Evaluation of established stable carbon isotope methods to
                                    determine their potential to distinguish contaminant vsnafura/
                                    organic carbon in subsurface materials on the basis of 13C/
                                    12C ratios. These experiments pertain to the origin of organic
                                    fractions in Category 5.
                                The approach to these objectives focused on aquifer materials
                                from reasonably well  characterized  fuel, solvent or organic
                                leachate contaminated as well as uncontaminated sites. Most of
                                these sites exhibited glacial orfluvioglacial geologic materials of
                                low organic carbon content. Volatile organic  compounds are
                                among the most common  ground-water contaminants  and
                                represent  significant  problems in quantitative sampling  and
                                analysis.

                                Experimental Procedures

                                Site Descriptions
                                The sites from which aquifer solid or ground-water samples were
                                collected are listed in Table 2.  Most of the samples were collected
                                by opportunity in the course of collaboration with other researchers.
                                                               Total Carbon (TC)
             Category


           1 INORGANIC/ORGANIC




           2 MATRIX
                        TIC
                Total Inorganic Carbon
                               POC
                     Particulate Organic Carbon
       TOC
Total Organic Carbon
                  DOC
        Dissolved Organic Carbon
           3 VOLATILITY
              (~40°C)
           4 EXTRACTABILTY
           5 ORIGIN
                                                                 1
                                                  VOCD           NVOCrj
       [ a) elemental, and b) specific compounds]    Volatile Dissolved Organic Carbon
                                        Solvent Extraction
                                            I)   H2O
                                            ii)   0.01 NKCI Solution
                                            Mi)  Methanol
                                            iv)  0.01 N KOH in Methanol: Toluene
                                                    (1:1 v/v)
            13Q/12Q ratios
[ a) elemental, and b) specific compounds]
Figure  1. Operational categories of subsurface carbon.

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Table 1. Separation and Analytical Methods  Corresponding to Selected Particulate Carbon Fractions
Category
                Carbon Fraction
                                             Subtraction
                           Separation
                                   Analysis
1 TIC

2 POC


3 VOCp
A/VOCp
a) VOCp
(elemental)
b) VOCp
(specific compounds)
CO2 removal by acidification of
TC1>2
Combustion of residue on
acidification of TC to release
CO/2
Infield preservation of
sub-cores3'4
Volatilization at >40°C
Volatilization at >40°C
CO2 by infrared spectro-
metry or coulometry
(as above)



Combustion of off-gases
O2 to CO2 (CO2 as above)
Dynamic or static head-
space GC with selective
                                                                                                  detectors
                a) A/VOCp
                 (elemental)
                b) A/VOCp
                 (specific compounds)
                       POC as above

                       Extraction  of solid sub-core
                       with organic solvents5
                                   POC as above

                                   Various gas or liquid
                                   chromatographic methods
                A/VOCD
                VOCp (a)
                (elemental)

                A/VOCp (a)
                (elemental)

                VOCp (b)
                (specific compound)
                A/VOCp (b)
                (specific compound)
i) weakly-sorbed
 room temperature
 (extraction
 solvent)
ii)  weakly-sorbed/
 ion-exchangeable
Hi) strongly sorbed/
 Hydrogen-bonded
iv) bound/occluded5'6
H20
0.01NKCI solution

Methanol

0.01 NKOH in Methanol:Toluene
(1:1  v/v)

Volatilization at >40°C off-gas
combustion in O2 to CO2

Combustion of residue from
volatilization in O2 to CO2

GC separation of off-gas from
volatilization step followed by
on-line combustion in  O2 to CO2

GC separation of solvent
extraction from 3 or 4 above
followed by on-line  combustion
in O2 to CO2
Combustion of dried
sample extract at
950°C to CO2 with CO2
as determined in 1 above
                                                          Isotope-ratio mass
                                                          spectrometry of CO2

                                                          Isotope-ratio mass
                                                          spectrometry of CO2 7

                                                          Isotope-ratio mass
                                                          spectrometry of CO2
                                                          Isotope-ratio mass
                                                          spectrometry of CO2
GC = Gas Chromatography
1Powell et al. (1989).
2Caughey et al.  (1995).
3Hewitt et al. (1992).
4Siegrist and Jenssen (1990).
Barcelona et al. (1995).
^Modified from Cheng (1990).
7Waasenaar et al. (1991).

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Sampling Methods
Samples of aquifer solids and ground water were collected from
six sites contaminated with mixed organic wastes or petroleum
fuel  mixtures.  Water samples were collected  by pumping  or
bailing existing monitoring wells at three underground storage
tank (LIST) sites in Houston, Texas; the former site of Casey's
Canoe Livery  at Sleeping Bear Dunes State Park in  Empire,
Michigan;  an anaerobic  treatment impoundment  of  meat
processing wastes in Beardstown, Illinois; a clean site at Sand
Ridge State  Park in  Illinois;  and,  a fire-training  area  at
decommissioned Wurtsmith AFB in  Oscoda,  Michigan. The
sampling sites were all in shallow unconfined aquifers which had
experienced contamination over extended  time  periods (i.e.,
>minimum 5 years). With the exception of the Beardstown and
Sand Ridge sites, the other  sites had  known BTEX (benzene,
toluene, ethylbenzene and xylenes) contamination in the ground
water.

The water samples at the LIST sites were collected by  a private
consultant  under the direction of Dr.  Joseph Salanitro,  Shell
Development Co. Aquifer solid samples were subsampled from
rig drilled cores  at the  Sleeping Bear Dunes site. All  samples
were refrigerated at 4°C after collection and water samples were
preserved by adjustment to pH 10 with KOH. Samples for BTEX
determinations were preserved in the field with HCI to pH 2 prior
to refrigeration and transported to the laboratory.
                Analytical Methods
                The common elements in analytical determinations which were
                accomplished on categories 1, 2, 3a NVOCp, 4, and 5a, are that
                they could be referenced to verifiable primary standards. These
                include: National Institute  of  Standards Dolomite  Standard
                Reference Material (SRM) #88 and potassium hydrogen
                phthalate. The determinations of volatile fractions 3b) VOCp and
                NVOC were straightforward applications of U.S. EPA Methods
                601/6d2 (Keith,  1991) for  which there are  well-referenced
                standards. Elemental carbon determinations on VOC fractions
                were done on a compound specific basis (i.e., carbon content per
                compound) by static headspace capillary gas  chromatography
                using EPA 601/602 methods with simultaneous photoionization
                and electrolytic conductivity detectors. Unknown  compounds
                were quantified as dichloroethylene for chlorinated aliphatics or
                benzene for aromatic compounds. In  all cases VOCp samples
                were collected as cut-off syringe subcores (Hewitt, 1995) preserved
                with 50:50 methanol:H2O  or 1% NaHSO4 solution.

                The details of  the acidification and analysis steps for NVOCp
                determinations were modified from Acton and Barker (1992) and
                are reported in Caughey et al. (1995).  Four  aquifer material
                standards  of varying TOC/TC ratios were ground to pass 200
                mesh. Along with National  Institute of Standards SRM 88b-
                Dolomite, the ground  solid  samples were  distributed to  eight
                laboratories. These  test  materials  are described  in Table 3.
     Table 2. Description of Study Sites
     Site/(Location)
                                              Contaminant Mixture
                                 Geologic Materials
     Asylum Lake
      (Kalamazoo, Ml)

     Beardstown/Sand Ridge
     State Park
     (Central Illinois)
       Leachate

     Kalamazoo-Battle Creek
     Airport

     Service Station Sites
     (Houston,  TX)

     Sleeping Bear
     Dunes State Park
     (Empire, Ml)

     Wurtsmith  AFB
     (Oscoda,  Ml)
                                              None
Meat processing
treatment
impoundment
Fuels and solvents from aircraft
maintenance

Motor fuels from underground
tanks

Motor/heating fuels from under-
ground  tanks
Jet fuel,  chlorinated solvents
from  fire-training exercises
Glacial outwash sand/gravel-
postglacial alluvium1

Glacial sands with some
interbedded  gravels2
Glacial sands and gravels
with fill material1

Low permeability silty
sands/clays3

Coastal lacustrine sand-
dunes4
Fluvioglacial sands/gravels
with aeolian dune deposits5
     1Hydrogeology Field Course, Western Michigan University, Summer, 1992.
     2 Barcelona et al., 1989.
     3Personal  Communication, Dr. Joseph Salanitro, Shell Research, Houston, TX.
     "Westetal., 1994.
     5Cummings and Twenter,  1986.

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Overall, they covered a wide range of TIC at low TOC contents.
The TIC in the samples was contributed by dolomite (e.g., 99.5%
for Test Material  #1  (TM1)  to  mixed calcite  and dolomite
mineralogy. Reagent grade 6% H2SO3from the same lot was also
sentto each lab afterthe carbon content of the acid was measured
andconfirmedtobelessthan 1 |ig-C/ml. Round-robin participating
laboratories  were instructed to use the identical acidification
procedure employing  individual  samples of >0.1g for five
replicates on each  of the five test materials.

Solid samples  for parallel (i.e., duplicate solid portions for each
solvent) or sequential (i.e., one set of duplicate solid portions for
successive extraction by  all  solvents)  extraction by  the four
solvents were air dried,  and extracted at a  2:1  ratio of
solid:extractant(i.e., ~100g/50ml) in amber glass jars with PTFE
(polytetrafluoroethyiene)  lids. Extractions  were conducted at
room temperature for eight hours on a reciprocating shaker. The
slurries were then centrifuged at ~2000g for an hour and then
decanted. The extractions were  repeated, combined with the
previous decantate, volume  adjusted  and handled as water
samples for NVOC or specific organic compound determinations.

Stable carbon isotope determinations on NVOCp and TIC samples
were done by  the  method of Epstein et al.,  (1987) and CO32'
equilibration methods, respectively. Results were expressed in
conventional per mille (0/00) del (d) notation relative to the Pee
Dee Belemnite standard.

Results and Discussions
The full details of the results on each of the primary objectives of
the  work  are  contained  in literature publications.  The major
                       highlights of the results are discussed below with reference to the
                       publications.

                       Quantitative Determination of Non-Volatile
                       Organic Carbon  (NVOC)
                       Seven of the eight laboratories (designated A through G) fully
                       participated in the round-robin study of TIC removal methods of
                       NVOC determinations (Caughey et al., 1995). The details of their
                       execution of the round-robin  procedures are summarized in
                       Table 4. Initially  it was planned that mean reported TOC values
                       would be used as the target values with which laboratory accuracy
                       would  be compared. However, the errors in the datasets were
                       systematically biased rather than random and this was not
                       possible.  The pooled Total  Carbon (TC), TIC and  TOC  (i.e.,
                       NVOC) results for the study are shown in Table 5. Interlaboratory
                       agreement was  best for TC and TIC for all five test materials.
                       These results underscore the excellent accuracy and precision
                       of combustion and coulometric endpoints for CO2 quantitation.
                       The TOC results showed significant scatter, however, particularly
                       at high TIC to TOC ratios.

                       This study confirmed the results of previous literature contributions
                       citing incomplete TIC  removal as the most significant source of
                       error in NVOC determinations. Clearly, the use of commercial
                       sulfurous acid does not represent the answer to this problem.
                       This work and more recent efforts (Heron etal., 1996) commends
                       the use of strong non-oxidizing mineral acid  (e.g., H3PO4, HCI
                       etc.) for TIC removal from aquifer solids. The grinding of samples
                       to grain sizes less than  0.063 mm and belowis also recommended,
                       provided a shatterbox  ratherthan a high speed rotary grinder can
                       be used. The principal journal publication from this work(Caughey
Table 3. Test Material Descriptions
                                                                                  Approximate Values

Test
Material

Description
(depth interval)
Major Mineral
by x-ray Diffraction
XRD (Percentages)

TC
(mg g-1)

TOC
(mg g-1)

TIC
(mg g-1)
      1     NIST SRM 88b

      2     Aquifer material core A
             (76-98 cm)

      3     Aquifer material core A
             (262-284 cm)

      4     Aquifer materials core SC
             (317-415 cm)

      5     Aquifer material core 40
             (60-125 cm)
Dolomite, 99.5; quartz, 0.5

Quartz, 63.1; dolomite, 18.0;
 feldspars, 13.6; calcite, 5.2

Quartz, 87.0; feldspars, 5.9;
 dolomite, 5.5; calcite, 1.6

Quartz, 54.5; dolomite, 28.9;
 calcite, 9.4; feldspars, 7.2

Quartz, 91.6; feldspars, 5.2;
 dolomite, 2.6; calcite, 0.5
126.5

 28.8


 12.8


 48.2


 19.6
 0.5

 1.7


 2.1


 0.6


13.5
125.9

 27.2


 10.0


 46.9


  4.6

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 Table 4. Method Details for Seven Participating Laboratories
             Replicate
 Lab ID      Weight (mg)
                    Total Acid
                    Used  (ml)
                      TOO
                    Instrument
                                                   Comments
    C

    D
30-90


20-30


20-50

20-30


400-800
12


3-18

3-18


5-9
UIC 5000


LECO  WR-112


UIC 5000

UIC CM 120
                                                    LECO  CS-225;
                                                     Dohrmann DC1800
                                                                               Samples were acidified before
                                                                               transfer to combustion boats

                                                                               Porous combustion crucibles
                                                                               leaked acid
                                                                               Salt crust hindered sample acidi-
                                                                               fication
                                                                Used 2M HNO3 for acidification;
                                                                determined TOC as ASOC + AIOC
F
G
250-500
80-130
9-12
9
LECO CS-444
UIC
Did not determine TIC
 Table 5. Pooled Round-Robin Test Results for Carbon Determinations
Parameter
(units)
Pooled TOC mean
(mg C g-1)
Pooled TC mean
(mg C g-1)
Pooled TIC mean
(mg C g-1)
TOCEST
(mg C g-1)
TIC/TOCEST
TM 1
50.99*
(35.85)
[70%]
126.70
(1.84)
[1.5%]
125.67
(0.37)
[0.3%]
1.03
122
TM 2
5.07*
(5.79)
[114%]
28.84
(1.43)
[4.9%]
27.18
(0.74)
[2.7%]
1.66
16
Test Material
TM 3
2.75
(2.04)
[74%]
12.83
(0.78)
[6.1%]
9.97
(0.45)
[4.5%]
2.86
3.5
TM 4
11.87*
(13.84)
[117%]
48.54
(2.17)
[4.4%]
46.91
(1.00)
[2.1%]
1.63
29
TM 5
13.52
(2.16)
[16%]
19.63
(0.96)
[4.9%]
4.55
(0.92)
[20.3%]
15.08
0.30
NOTE:  Asterisks indicate biased values where the estimated error was greater than 100%.  Values in parentheses are standard
        deviations;  values in brackets are relative standard deviations.

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et al., 1995) provides a detailed description of the procedural
recommendations.

It should be noted that TOC errors of a factor of two or more would
have a significant impact on the value of Koc inputto an estimation
of retardation coefficients. This level of error may  be routinely
observed in samples with high TIC to TOC ratios (i.e., >10) and
dolomite percentages above  15%.  Practically, these analytical
problems  may  be expected in studies involving glacial or
carbonate aquifer solid  samples.

Evaluation of In-field Aquifer Solid Preservation
Techniques for VOC Determinations
There has been a great deal  of recent concurrent  work on the
preferred means of preservation of VOC samples. The results of
this work reported along with those of other groups (Siegrist and
van Ee, 1994) and (Wisconsin DNR, 1994) strongly support the
following:

1)  Immediate field preservation of core material  in 40  ml of
    headspace  vials with mineral  acid,  methanol, or sodium
    bisulfate  is  necessary  to   perform accurate  VOC
    determinations;

2)  Syringe sub-sample collection from cores minimizes sample
    disturbance and handling time  which leads to higher and
    more  reproducible  recoveries;

3)  Negative bias (i.e., low results) levels are  greater  for
    compounds which are more volatile and less strongly sorbed;
    and

4)  Bulk jar sampling of core materials without  preservation
    other than refrigeration leads to  gross negative bias in VOC
    determinations.

The limited results of the present study were  in close agreement
with those of more systematic investigations reported above. The
primary references including Barcelona etal., 1993 and Barcelona
et al., 1995 should be consulted for complete details.

Extractability ofNVOC by Solvents of High to
Medium Polarity
Fifteen samples  of aquifer materials from  several sites  were
taken in parallel (i.e., individual solid samples for each extraction
solution) and sequentially (i.e., single solid samples taken through
the series of extractions). The extracting  solutions and the
operational leachability fraction they represent included:
   Extractant

 1. Distilled H2O

 2. 0.01 N KCI

 3. Methanol (MeOH)

 4. MeOH-0.01N
   (KOH/Toluene)
   (1:1 V/V)
     Leachability Fraction

Weakly Sorbed

Weakly Sorbed/lon Exchangeable

Strongly Sorbed/Hydrogen Bonded

Bound/Occluded
The results of these extractions are shown in Tables 6 and 7 for
the parallel and sequential methods, respectively.  In general,
MeOH and the MeOH-KOH/toluene extracted more of the total
extractable carbon than the aqueous solvents (e.g., H2O and KCI
solution). For both contaminated and uncontaminated solids, the
percent carbon extractable  by the aqueous  based solvents,
which might be leached easily, was less than 50% of the total.
Parallel extraction tended to extract more total carbon than the
sequential method. This might be explained by the full rehydration
of the solid samples by the preceding aqueous extractions in the
sequential  case which reduced  the effectiveness of stronger
solvents.

The  extractability of carbon from the Sleeping Bear  Dunes
samples is shown graphically in Figure 2. There was a clear trend
in apparent leachability as a function of position in the flow field.
That is, source zone organic matter was less extractable than
background or downgradient samples.  This may be expected
due to lower hydraulic conductivity and perhaps interconnected
pore space near fuel product  masses.  It was unresolved why
methanol and the alkaline methanol:toluene differed greatly in
their extractability of the  hydrocarbon contaminants.

Evaluation of Stable Carbon Isotope
Characteristics of Major Carbon Fractions
In this portion of the work  it  was anticipated that significant
differences could be observed in the stable carbon isotopic ratios
(i.e., 13C/12C) between TIC and TOC fractions. This was because
of their likely carbonate mineral and  plant matter origins,
respectively. Mineral carbonates typically show d13C values of ~0
o/oo relative to the Pee Dee Belemnite standard. Organic carbon
from fossil fuels and plants exhibit d13C values -20 to -28 o/oo. In
the d notation, this reflects depletion of 13C relative to the standard
in parts perthousand and  is termed isotopically depleted (lighter).
It was also hoped that petroleum contaminated samples would
differ significantly in  13C/12C ratios from both of the above end
members and isotopic shifts (Suchomel et al., 1990) or in  PIC or
POC fractions from transformation of the contaminants.

The samples for this part of the  study were collected from the
Sleeping Bear Dunes, Beardstown and Sand Ridge sites which
were  petroleum or meat  processing contaminated and
uncontaminated, respectively.

The limited selection of sampling sites and types of contamination
did not permit a comprehensive conclusion to  be drawn  on the
utility  of stable carbon isotope determinations to  differentiate
natural organic carbon from fuel hydrocarbons in aquifer  solids.
A summary of the overall data set (Table 8) suggests that distinct
differences in the d13C signatures of NVOC and PIC exist between
both the saturated and unsaturated zones at contaminated and
uncontaminated sites. Unsaturated zone d13C natural  NVOC
was ~6 o/oo heavier than that in the saturated zone possibly
reflecting transformation of the  original organic mixture. A recent
study by Landmeyeretal. (1996) should be consulted for the use
of d13C signatures as a function  of the redox environment in which
transformations proceed.

The petroleum contaminated samples from the Sleeping Bear
site were intermediate between these values. This indicated that
the weathered fuels at this site were quite close to plant-derived
organic matter in stable carbon isotope characteristics. In general,
fossil  liquid hydrocarbon mixtures as well  as  refined products

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 Table 6. Average Organic Carbon In Parallel Extracts of Aquifer Solids
                                                            Extracts
Sample
1001
1002
2
3
4
5
6
7
8
9

10
11
12
13
14
15
SB Background 54E
5.5-6.0
WMU AP/NPWH
Airport Spill
SB-40' Cluster 4.9-7.4'
Carson City Ref. 16'
SB-90' Cluster 5.0-7.8'
SB-90' Cluster 2.0-4.7'
SB-40' Cluster 4.8-6.9'
SB-40' Cluster 2.0-4.1'
SB-Source Cluster 10.6-13.6'
SB-Source Cluster 7.4-10.5
ASYLUM LAKE
AL-5'
AL-15'
AL-25'
AL-35'
AL-45'
AL-55'
Total C
(mg/g)
770
1730
4600
722
1111
2433
658
8322
1020
1162

1223
615
317
806
123
123
H20
82.3
180
54.7
21.3
31.0
73.6
45.1
87
14.7
<1.0

2.7
0
11.4
34.8
16.6
-
-
17.2
KCI
(mg C/g)
47.9
123
15.0
32.0
18.7
47
110
43.5
<1.0
57

<1.0
5.8
28.6
51.3
61.3
-
-
112
Methanol
114
377
146
80.2
48
<1.0
31.3
45.9
129
12.5

11.7
5.9
31.4
65.7
37.8
-
-
36.4
KOH/
methanol
toluene
187
326
230
201
135
<1.0
37.9
229
21.0
37.6

51.2
61.2
119
163

-
-
34.0
Total
Extract Percent
(mg C/g) Extractable
431
1006
446
335
233
121
224
405
165
107

66
72.9
190
314
116
-
-
199.6
56
58
10
46
21
5
34
5
16
9

5
6*
31
51"
37
-
-
162
 - = samples too low for quantitation
 * replicate determinations (other chemists)
 SB samples = Sleeping Bear Dunes, Empire, Michigan
range between -24 to -30 o/oo d13C. Contaminated ground water
and soil gas samples from this site were somewhat heavier -22.3
o/oo (n=1) and -22.9 + 0.1 (n=4),  respectively. These samples
reflect an isotopic shift towards heavier isotopic signatures which
could be expected from microbial remineralization  of  either
natural plant or petroleum-related organic carbon.

It was clear from these  data that though the stable isotopic
differences between plant  and weathered-petroleum product
organic carbon were not overwhelming they were significant and
measurable. The work of Suchomel etal. (1990) incorporated 14C
determinations into the interpretation of stable carbon ratios and
the origin of organic matter. Their approach should be valuable
in  identifying the  contribution of recent or synthetic carbon in
NVOC mixtures in aquifer solids.

Conclusion
The focus of this work was the evaluation of analytical methods
to  determine and characterize fractions of subsurface organic
matter. Major fractions of total  organic carbon (TOC)  include:
particulate organic carbon (POC) in aquifer material, dissolved
organic carbon (DOC) and both volatile (VOC) and non-volatile
(NVOC) organic carbon subfractions.

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 Table 7. Average Organic Carbon In Sequential Extractions of Aquifer Solids
                                                        Extracts
Sample
1001 SB Background 54E
5.5-6.0'
1002 WMU AP/NPWH
Airport Spill
2 SB-40' Cluster 4.9-7.4'
3 Carson City Ref. 16'
4 SB-90' Cluster 5.0-7.8'
5 SB-90' Cluster 2.0-4.7'
6 SB-40' Cluster 4.8-6.9'
7 SB-40' Cluster 2.0-4.1'
8 SB-Source Cluster 10.6-13.6'
9 SB-Source Cluster 7.4-10.5
ASYLUM LAKE
10 AL-5'
11 AL-15'
12 AL-25'
13 AL-35'
14 AL-45'
15 AL-55'
Total C
(mg/g)
770
1730
4600
722
1111
2433
658
8322
1020
1162

1223
615
317
806
123
123
H20
91.7
60.6
0
5.7
30.5
22.6
4.0
9.3
0
16.6

-
-
52.6
0.9
11.7
25.6
KCI
(mg C/g)
13.9
59.1
6.4
0
6.2
64.7
0
0
35.6
82.5

-
-
58.6
6.8
22.5
162
Methanol
104
75.2
17.2
6.0
65.2
82.4
32.4
46.0
53.5
45.0

-
-
67.1
44.4
110
54.5
KOH/
methanol
toluene
4.6
66.4
7.5
0
57.4
36.5
30.2
24.2
41.0
60.3

-
-
53.4
16.6
31.7
51.6
Total
Extract
(mg C/g)
214
261
31.1
11.7
159
206
66.6
79.5
130
204

-
-
232
68.7
175.9
294
Percent
Extractable
27.8
15.1
0.7
1.6
14.3
8.5
10.1
1.0
12.8
17.6

-
-
73.0
8.5
143
239
   - = samples too low for quantitation.
 SB = Sleeping Bear Dunes, Empire, Michigan.
POC makes  up the  bulk of TOC in contaminated  and
uncontaminated subsurface soils and  aquifer materials. The
volatile subfraction  of POC can be  determined  quantitatively
when minimally disturbed subcores are preserved immediately
in the field. Methanol and acid addition (i.e., HCI, NaHSO4) to
pH 2 are adequate preservatives for specific volatile organic
compound determinations. An interlaboratory round-robin test to
improve acidification and  removal  methods for carbonates in
total carbon using sulfurous acid (H2SO3) showed sensitivity to
several factors. Thesefactors include: operator care, acid strength
and carbon content, and particularly, the incomplete removal of
inorganic carbon at high total carbon to organic carbon ratios.

The extractability of POC by a range of high to medium polarity
solvents resulted in the observations that relatively little POC was
extractable and water  extracted comparable amounts to  1:1
mixtures of 0.1M  KOH in  methanol:toluene. Stable  isotopic
characteristics of  NVOC  from fuel  contaminated and organic-
enriched environments were found to be quite sensitive to the
stable isotopic signatures of natural organic matter.

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                                                                   ORG. CARBON
                                H2O

                                0.1 NKCL


                                MeOH

                                MeOH-0.01NKOH/TOL
                                             Q.
                                             UJ
                                             Q
                                             O
                                             o
                                                    BKGRD-54E
                                                       (0.1)
SOURCE (1.0)
                                                   SOURCE (1.8)
                                                       12m (0.4)
   12m (1.3)
   12m (1.5)
                                                      27m (0.5)
                                                      27m (2.0)   §
                                                                     50    100   150     200    250
     Figure 2. Average Extractable Organic Carbon for Selected Sleeping Bear Dunes Samples (mg/g). Locations are designations: background,
              in source area, and 12m and 27m downgradient from source, respectively. Parentheses denote depth in meters below land surface
              at each location.


Table 8. Summary of Average 13C/t2C (d o/oo)  Ratios in Non-Volatile Carbon Fractions
                                    (parentheses denote relative standard derivations)
                                         Organic Carbon     n	Inorganic Carbon   n
Uncontaminated
Unsaturated Zone


Saturated Zone


SR
BTU
BTD
SR
BTU
-21.5
-22.5
-22.1
-27.6
-28.2
(17%) 4
(11%) 2
(5%) 6
(1.
(1.
,5%) 3
,4%) 10
-15.7 (25%) 3
-19.2 1
-22.1 (9%) 6
0.8 1
-14.1 (28%) 3
Contaminated
Saturated Zone

SR
SB
BTU
BTD

Sand Ridge.
BTD
SB

-27.1
-25.5

(6.
(0.

,3%) 4
.1%) 6

0.5 1
0.0 1

Sleeping Bear.
Beardstown
Beardstown
Upgradient.
Downgradient.
                                                               10

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Acknowledgement
TheauthorswishtothankMs. BonnieDube, Ms. Carolyn Virkhaus,
and Mrs. Debbie  Patt for their assistance in the work. The
guidance and support of Candida C.  West, the EPA Project
Officer, is very much appreciated.

Disclaimer
The U.S. Environmental Protection Agency through its Office of
Research and Development partially funded and collaborated in
the research described here under Cooperative Agreement No.
CR-817287 to Western Michigan University. It has been subjected
to the Agency's peer and administrative review and has been
approved for publication as an EPA document. Mention of trade
names or commercial products does not constitute endorsement
or recommendation for use.
                                                         11

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