1

Characterization of Organic Matter in

Soil and Aquifer Solids

M.J. Barcelona,a M.E. Caughey,

b

 R.V. Krishnamurthy,

c

 D.M. Shaw,c and K. Maasc

National Risk Management

Research Laboratory

Ada, OK 74820

United States

Environmental Protection

Agency

Research and Development

ENVIRONMENTAL

RESEARCH BRIEF

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. , HCl, 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 (H2

SO3) showed sensitivity to

several factors. These factors include: operator care, acid strength

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

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 processlevel hydrogeological investigations.

aDepartment of Civil and Environmental Engineering, University of Michigan, Ann

Arbor, MI 48109-2099.

bOffice of Environmental Chemistry, Illinois State Water Survey, Champaign, IL

61820.

cDepartments of Geology and Chemistry, Western Michigan University,

Kalamazoo, MI 49008.

EPA/600/S-97/001 April 1997
2

Figure 1. Operational categories of subsurface carbon.

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 (NVOCp

) 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 VOCp 

and NVOCp 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 vs natural

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 or fluvioglacial 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.
3

Table 1. Separation and Analytical Methods Corresponding to Selected Particulate Carbon Fractions

Category Carbon Fraction Subfraction Separation Analysis

1 TIC CO2

 removal by acidification of CO2 by infrared spectroTC1,2 metry or coulometry

2 POC Combustion of residue on (as above)

acidification of TC to release

CO2

1,2

3 VOCPInfield preservation of

NVOCP

sub-cores3,4

a) VOCP Volatilization at >40OC Combustion of off-gases

 (elemental) O2

 to CO2 (CO2 as above)

b) VOCP Volatilization at >40OC Dynamic or static head-

 (specific compounds) space GC with selective

detectors

a) NVOCP POC as above POC as above

 (elemental)

b) NVOCP Extraction of solid sub-core Various gas or liquid

 (specific compounds) with organic solvents5 chromatographic methods

4 NVOCP

i) weakly-sorbed H2O Combustion of dried

 room temperature sample extract at

 (extraction 950OC to CO2

 with CO2

 solvent) as determined in 1 above

ii) weakly-sorbed/ 0.01NKCl solution

 ion-exchangeable

iii) strongly sorbed/ Methanol

 Hydrogen-bonded

iv) bound/occluded5,6 0.01NKOH in Methanol:Toluene

(1:1 v/v)

5 VOCP

 (a) Volatilization at >40OC off-gas Isotope-ratio mass

(elemental) combustion in O2

 to CO2spectrometry of CO2

NVOCP (a) Combustion of residue from Isotope-ratio mass

(elemental) volatilization in O2

 to CO2spectrometry of CO2

 7

VOCP (b) GC separation of off-gas from Isotope-ratio mass

(specific compound) volatilization step followed by spectrometry of CO2

on-line combustion in O2 to CO2

NVOCP (b) GC separation of solvent Isotope-ratio mass

(specific compound) extraction from 3 or 4 above spectrometry of CO2

followed by on-line combustion

in O2

 to CO2

GC = Gas Chromatography

1Powell et al. (1989).

2Caughey et al. (1995).

3Hewitt et al. (1992).

4Siegrist and Jenssen (1990).

5Barcelona et al. (1995).

6Modified from Cheng (1990).

7Waasenaar et al. (1991).
4

Table 2. Description of Study Sites

Site/(Location) Contaminant Mixture Geologic Materials

Asylum Lake None Glacial outwash sand/gravel-

 (Kalamazoo, MI) postglacial alluvium1

Beardstown/Sand Ridge Meat processing Glacial sands with some

State Park treatment interbedded gravels2

(Central Illinois) impoundment

Leachate

Kalamazoo-Battle Creek Fuels and solvents from aircraft Glacial sands and gravels

Airport maintenance with fill material1

Service Station Sites Motor fuels from underground Low permeability silty

(Houston, TX) tanks sands/clays3

Sleeping Bear Motor/heating fuels from under- Coastal lacustrine sandDunes State Park ground tanks dunes4

(Empire, MI)

Wurtsmith AFB Jet fuel, chlorinated solvents Fluvioglacial sands/gravels

(Oscoda, MI) from fire-training exercises 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.

4West et al., 1994.

5Cummings and Twenter, 1986.

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 (UST) 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 UST 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 4oC after collection and water samples were

preserved by adjustment to pH 10 with KOH. Samples for BTEX

determinations were preserved in the field with HCl 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

NVOCp

 were straightforward applications of U.S. EPA Methods

601/602 (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 88bDolomite, the ground solid samples were distributed to eight

laboratories. These test materials are described in Table 3.
5

Table 3. Test Material Descriptions

Approximate Values

Major Mineral

Test Description by x-ray Diffraction TC TOC TIC

Material (depth interval) XRD (Percentages) (mg g-1) (mg g-1) (mg g-1)

1 NIST SRM 88b Dolomite, 99.5; quartz, 0.5 126.5 0.5 125.9

2 Aquifer material core A Quartz, 63.1; dolomite, 18.0; 28.8 1.7 27.2

 (76-98 cm) feldspars, 13.6; calcite, 5.2

3 Aquifer material core A Quartz, 87.0; feldspars, 5.9; 12.8 2.1 10.0

 (262-284 cm) dolomite, 5.5; calcite, 1.6

4 Aquifer materials core SC Quartz, 54.5; dolomite, 28.9; 48.2 0.6 46.9

 (317-415 cm) calcite, 9.4; feldspars, 7.2

5 Aquifer material core 40 Quartz, 91.6; feldspars, 5.2; 19.6 13.5 4.6

 (60-125 cm) dolomite, 2.6; calcite, 0.5

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% H2

SO3 from the same lot was also

sent to each lab after the carbon content of the acid was measured

and confirmed to be less than 1 μg-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

(polytetrafluoroethylene) 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 CO3

2-

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 et al., 1996) commends

the use of strong non-oxidizing mineral acid (e.g., H3

PO4, HCl

etc.) for TIC removal from aquifer solids. The grinding of samples

to grain sizes less than 0.063 mm and below is also recommended,

provided a shatterbox rather than a high speed rotary grinder can

be used. The principal journal publication from this work (Caughey
6

 Table 4. Method Details for Seven Participating Laboratories

Replicate Total Acid TOC

Lab ID Weight (mg) Used (ml) Instrument Comments

A 30-90 9 UIC 5000 Samples were acidified before

transfer to combustion boats

B 20-30 12 LECO WR-112 Porous combustion crucibles

leaked acid

C 20-50 3-18 UIC 5000

D 20-30 3-18 UIC CM 120 Salt crust hindered sample acidification

E 400-800 5-9 LECO CS-225; Used 2M HNO3

 for acidification;

 Dohrmann DC1800 determined TOC as ASOC + AIOC

F 250-500 9-12 LECO CS-444 Did not determine TIC

G 80-130 9 UIC

 Table 5. Pooled Round-Robin Test Results for Carbon Determinations

Parameter Test Material

(units) TM 1 TM 2 TM 3 TM 4 TM 5

Pooled TOC mean 50.99* 5.07* 2.75 11.87* 13.52

 (mg C g-1) (35.85) (5.79) (2.04) (13.84) (2.16)

[70%] [114%] [74%] [117%] [16%]

Pooled TC mean 126.70 28.84 12.83 48.54 19.63

 (mg C g-1) (1.84) (1.43) (0.78) (2.17) (0.96)

[1.5%] [4.9%] [6.1%] [4.4%] [4.9%]

Pooled TIC mean 125.67 27.18 9.97 46.91 4.55

 (mg C g-1) (0.37) (0.74) (0.45) (1.00) (0.92)

[0.3%] [2.7%] [4.5%] [2.1%] [20.3%]

TOCEST 1.03 1.66 2.86 1.63 15.08

(mg C g-1)

TIC/TOCEST 122 16 3.5 29 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.
7

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 input to 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 et al., 1993 and Barcelona

et al., 1995 should be consulted for complete details.

Extractability of NVOC 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 Leachability Fraction

1. Distilled H2O Weakly Sorbed

2. 0.01N KCl Weakly Sorbed/Ion Exchangeable

3. Methanol (MeOH) Strongly Sorbed/Hydrogen Bonded

4. MeOH-0.01N Bound/Occluded

(KOH/Toluene)

(1:1 V/V)

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 KCl

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 d

13C values of ~0

o/oo relative to the Pee Dee Belemnite standard. Organic carbon

from fossil fuels and plants exhibit d

13C values -20 to -28 o/oo. In

the d notation, this reflects depletion of 13C relative to the standard

in parts per thousand 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 d

13C 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 Landmeyer et al. (1996) should be consulted for the use

of d

13C 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
8

Table 6. Average Organic Carbon In Parallel Extracts of Aquifer Solids

 Extracts

KOH/ Total

Total C KCl methanol Extract Percent

Sample (mg/g) H2O (mg C/g) Methanol toluene (mg C/g) Extractable

1001 SB Background 54E 770 82.3 47.9 114 187 431 56

5.5-6.0

1002 WMU AP/NPWH 1730 180 123 377 326 1006 58

Airport Spill

2 SB-40' Cluster 4.9-7.4' 4600 54.7 15.0 146 230 446 10

3 Carson City Ref. 16' 722 21.3 32.0 80.2 201 335 46

4 SB-90' Cluster 5.0-7.8' 1111 31.0 18.7 48 135 233 21

5 SB-90' Cluster 2.0-4.7' 2433 73.6 47 <1.0 <1.0 121 5

6 SB-40' Cluster 4.8-6.9' 658 45.1 110 31.3 37.9 224 34

7 SB-40' Cluster 2.0-4.1' 8322 87 43.5 45.9 229 405 5

8 SB-Source Cluster 10.6-13.6' 1020 14.7 <1.0 129 21.0 165 16

9 SB-Source Cluster 7.4-10.5 1162 <1.0 57 12.5 37.6 107 9

ASYLUM LAKE

10 AL-5' 1223 2.7 <1.0 11.7 51.2 66 5

0 5.8 5.9 61.2 72.9 6*

11 AL-15' 615 11.4 28.6 31.4 119 190 31

34.8 51.3 65.7 163 314 51*

12 AL-25' 317 16.6 61.3 37.8 116 37

13 AL-35' 806 - - - - - -

14 AL-45' 123 - - - - - -

15 AL-55' 123 17.2 112 36.4 34.0 199.6 162

- = samples too low for quantitation

* replicate determinations (other chemists)

SB samples = Sleeping Bear Dunes, Empire, Michigan

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.

range between -24 to -30 o/oo d

13C. 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 et al. (1990) incorporated 14C

determinations into the interpretation of stable carbon ratios and
9

Table 7. Average Organic Carbon In Sequential Extractions of Aquifer Solids

 Extracts

KOH/ Total

Total C KCl methanol Extract Percent

Sample (mg/g) H2O (mg C/g) Methanol toluene (mg C/g) Extractable

1001 SB Background 54E 770 91.7 13.9 104 4.6 214 27.8

5.5-6.0'

1002 WMU AP/NPWH 1730 60.6 59.1 75.2 66.4 261 15.1

Airport Spill

2 SB-40' Cluster 4.9-7.4' 4600 0 6.4 17.2 7.5 31.1 0.7

3 Carson City Ref. 16' 722 5.7 0 6.0 0 11.7 1.6

4 SB-90' Cluster 5.0-7.8' 1111 30.5 6.2 65.2 57.4 159 14.3

5 SB-90' Cluster 2.0-4.7' 2433 22.6 64.7 82.4 36.5 206 8.5

6 SB-40' Cluster 4.8-6.9' 658 4.0 0 32.4 30.2 66.6 10.1

7 SB-40' Cluster 2.0-4.1' 8322 9.3 0 46.0 24.2 79.5 1.0

8 SB-Source Cluster 10.6-13.6' 1020 0 35.6 53.5 41.0 130 12.8

9 SB-Source Cluster 7.4-10.5 1162 16.6 82.5 45.0 60.3 204 17.6

ASYLUM LAKE

10 AL-5' 1223 - - - - - -

11 AL-15' 615 - - - - - -

12 AL-25' 317 52.6 58.6 67.1 53.4 232 73.0

13 AL-35' 806 0.9 6.8 44.4 16.6 68.7 8.5

14 AL-45' 123 11.7 22.5 110 31.7 175.9 143

15 AL-55' 123 25.6 162 54.5 51.6 294 239

 - = 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., HCl, 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 (H2

SO3) showed sensitivity to

several factors. These factors 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 organicenriched environments were found to be quite sensitive to the

stable isotopic signatures of natural organic matter.
10

Table 8. Summary of Average 13C/12C (d o/oo) Ratios in Non-Volatile Carbon Fractions

 (parentheses denote relative standard derivations)

 Organic Carbon n Inorganic Carbon n

Uncontaminated

Unsaturated Zone SR -21.5 (17%) 4 -15.7 (25%) 3

BTU -22.5 (11%) 2 -19.2 1

BTD -22.1 (5%) 6 -22.1 (9%) 6

Saturated Zone SR -27.6 (1.5%) 3 0.8 1

BTU -28.2 (1.4%) 10 -14.1 (28%) 3

Contaminated

Saturated Zone BTD -27.1 (6.3%) 4 0.5 1

SB -25.5 (0.1%) 6 0.0 1

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.

SR Sand Ridge.

SB Sleeping Bear.

BTU Beardstown Upgradient.

BTD Beardstown Downgradient.

ORG. CARBON (μg/g)
11

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Acknowledgement

The authors wish to thank Ms. Bonnie Dube, 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.
12

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