R. Paul Philp, School of GeologyR. Paul Philp, School of Geologyand Geophysics, University ofand Geophysics, University ofOklahoma, Norman, OK. 73019.Oklahoma, Norman, OK. 73019.

THE EMERGENCE OF STABLETHE EMERGENCE OF STABLEISOTOPES IN ENVIRONMENTALISOTOPES IN ENVIRONMENTALAND FORENSIC GEOCHEMISTRYAND FORENSIC GEOCHEMISTRY

STUDIESSTUDIES

Forensic GeochemistryForensic Geochemistry•• Environmental forensic studiesEnvironmental forensic studiesgenerally involve a product,generally involve a product,typically organic, released intotypically organic, released intosome type of environment, such assome type of environment, such aslakes, rivers, oceans, orlakes, rivers, oceans, orgroundwater. However with anygroundwater. However with anyincident the questions asked areincident the questions asked arealmost always the samealmost always the same..

SO WHO DID IT?SO WHO DID IT?

Important questions:Important questions: What is it?What is it?Where did it come from? Who didWhere did it come from? Who didit?it?

Bottom line:Bottom line: Who is going to pay toWho is going to pay toclean it up?clean it up?

Forensic GeochemistryForensic Geochemistry

•• Techniques commonly used toTechniques commonly used toanswer these questions:answer these questions:

Gas Chromatography (GC)Gas Chromatography (GC)

Gas ChromatographyGas Chromatography--MassMassSpectrometry (GCMS)Spectrometry (GCMS)

Minutes

0 7 14 21 28 35 42 49 56 63

700 7 14 21 28 35 42 49 56 63 70

Minutes0 7 14 21 28 35 42 49 56 63 70

Minutes

0 7 14 21 28 35 42 49 56 63 70

Gasoline

Condensate JP4

Diesel

Fingerprinting by Gas Chromatography

Crude Oil ChromatogramCrude Oil Chromatogram

0

C17

C35

Pristane

Phytane

Processes acting on spilledproducts

Weathering Effects of CrudeWeathering Effects of CrudeOilsOils

C18

C12

C26

C15EVAPORATED OILb

C18

C28

C26

BIODEGRADED OILAFTER 1 MONTH

d

C12

C15

C18

C26

WATER-WASHED OILc

C18

C15

C31C26

BIODEGRADED

2 MONTHS

e

OIL AFTER BIODEGRADED OILAFTER 4 MONTHS

f

C18

C15

C12

C26

INITIAL OILa

STEROL/STERANE BIOMARKERSSTEROL/STERANE BIOMARKERS

STEROL STERANE

HO

M/z 217 Sterane Chromatogram

M/z 191 Terpane Chromatogram

Tricyclics Hopanes

Biomarker Distributions

Forensic GeochemistryForensic Geochemistry•• GC and GCMSGC and GCMS--powerful, wellpowerful, wellestablished, used extensively inestablished, used extensively inlitigation.litigation.

•• Additional evidence required when GCAdditional evidence required when GCand GCMS are of limited, or no, useand GCMS are of limited, or no, use--((i.ei.e. single components or refined. single components or refinedproducts.)products.)

•• In these situations stable isotopes areIn these situations stable isotopes arebeing used to provide additionalbeing used to provide additionalinformation.information.

What are Isotopes?What are Isotopes?Atoms of same element with differing masses;Atoms of same element with differing masses;

same # of protons, different # of neutronssame # of protons, different # of neutrons

ppee--

Hydrogen,1H

nnpp

ee--

Deuterium,Deuterium,22H, DH, D

nnpp nn

ee--

Tritium,Tritium,33H, TH, T

Sum of protons and neutrons is the atomic massSum of protons and neutrons is the atomic mass

Lighter HeavierLighter Heavier

What are Stable Isotopes?What are Stable Isotopes?

•• Carbon exists as two stable isotopes,Carbon exists as two stable isotopes,1212C andC and 1313C which differ in theC which differ in thenumber of neutrons they contain.number of neutrons they contain. 1212CChas 6 electrons, 6 protons and 6has 6 electrons, 6 protons and 6neutrons;neutrons; 1313C has 7 neutrons.C has 7 neutrons. 11H hasH has1 electron and 1 proton and1 electron and 1 proton and 22H has 1H has 1electron, 1 proton and 1 neutron.electron, 1 proton and 1 neutron.

Other Isotopes ofOther Isotopes ofEnvironmental InterestEnvironmental Interest

•• Chlorine (Chlorine (3535Cl/Cl/3737ClCl-- 75.53/24.47)75.53/24.47)

•• Sulfur (Sulfur (3232S/S/3434SS--94.02/3.21)94.02/3.21)

•• Nitrogen (Nitrogen (1414N/N/1515NN--99.64/0.36)99.64/0.36)

Data OutputData Output--Isotope ScaleIsotope Scale

-50.00 -40.00 -30.00 -20.00 -10.00 0.00 10.00

PDB Standard

δ13CIsotopically lighter

Isotopically depleted

More negative

10001RRCδ

standard

sample13 ×

−= R = 13C/12C

Forensic GeochemistryForensic Geochemistry

•• Stable isotopes utilized inStable isotopes utilized ingeochemical applications for moregeochemical applications for more

than 50 years.than 50 years.

Source A

Source B

Toluene

Toluene

GC-FID

or

GCMS

Single Component ContaminantsSingle Component Contaminants

When thecontaminant is asingle component-how can youdistinguish onefrom another? GCand GCMS no help.

Isotopes may bedifferent

AllocationAllocation –– 2 Sources2 Sources

TolueneToluene δδ1313C orC or δδ22H: 2 sources, single tracerH: 2 sources, single tracer

Source B:δ13C -25‰δ2H -150‰

Source A:δ13C -30‰δ2H -200‰

Plumeδ13C -29‰δ2H -190‰

Plume = 80% Source A, 20% Source B

Prince William Sound Residues

Exxon Valdez Oil

Terpanes in Prince WilliamSound Residues

-24.5

-28.7-24.1

-29.1R

Forensic GeochemistryForensic Geochemistry

•• More recently the combination ofMore recently the combination ofgas chromatography with isotopegas chromatography with isotope

ratio mass spectrometry (GCIRMS)ratio mass spectrometry (GCIRMS)has lead to a significant increase inhas lead to a significant increase inthe number of isotopic applications.the number of isotopic applications.

Refined ProductsRefined Products

•• For example diesel derived fromFor example diesel derived fromdifferent crude oils can bedifferent crude oils can bedifferentiated using carbon anddifferentiated using carbon andhydrogen isotopic compositions.hydrogen isotopic compositions.

•• Isotope data can be supported byIsotope data can be supported byvarious biomarkers not commonly usedvarious biomarkers not commonly usedin environmental studies:in environmental studies:sesquiterpanessesquiterpanes;; adamantanesadamantanes; and; anddegraded steranesdegraded steranes..

Diesel Fingerprints

Isoprenoid Isotope Fingerprints

California

Oklahoma

-32

-30

-28

-26

-24

-22

-20

C14

i

C15

i

C16

i

C18

i

PR PH

Car

bon

Isot

ope

Val

ue

Forensic Geochemistry

Site A

Site B

Groundwater flow direction

MW 1

B

C

MW6

Weathered and Unweathered Diesel

Diesel MW 6

Diesel MW 1 Pr

Ph

C17

-27

-26

-25

-24

-23

-22

-21

-20C

14i

C15

i

C16

i

C18

i

PR PH

MW 6

MW 1

Carbon Isotope Values for Isoprenoids

Adamantanes in Diesel Fuels

C13C12C11

Diesel MW 1

Diesel MW 6

GasolinesGasolines•• Gasolines from differentGasolines from differentsources often have very similarsources often have very similarchromatograms.chromatograms.

•• GasolinesGasolines are devoid ofare devoid ofbiomarkers, further limitingbiomarkers, further limitingcorrelation possibilities.correlation possibilities.

•• One solution is to use GCIRMSOne solution is to use GCIRMSfor both the hydrocarbons andfor both the hydrocarbons andadditivesadditives..

Comparison of Gasolines by GC

-35.00

-33.00

-31.00

-29.00

-27.00

-25.00

-23.00

-21.00

LECOECFOKGOK

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45

δ13 C

(‰)

Peak Number

Carbon Isotopic Composition of Gasolines fromCarbon Isotopic Composition of Gasolines fromOklahoma (FOK, GOK) and the East Coast (LEC, OEC)Oklahoma (FOK, GOK) and the East Coast (LEC, OEC)

This figure shows the carbon isotopic fingerprint of gasolines sampled from Oklahoma andfrom the East Coast and demonstrates that these gasolines are significantly different interms of isotopic composition and can be discriminated from each other on this basis.The peak numbers are identified in the section above.

Coal Tar-PAHs

PAHs and Stable IsotopesPAHs and Stable Isotopes

•• Current interest is in discriminatingCurrent interest is in discriminatingPAHs derived from formerPAHs derived from formermanufactured gas plant (MGP) wastesmanufactured gas plant (MGP) wastesversus those from general urbanversus those from general urbanbackground aromaticsbackground aromatics

•• Urban backgrounds have a fairlyUrban backgrounds have a fairlynarrow range and small differencesnarrow range and small differencesmay be related to source differencesmay be related to source differences

07

08

-35.00-33.00-31.00-29.00-27.00-25.00-23.00-21.00

14 16 18 20 22 24 26 29 32 9D 16D

24D

Peak ID

Car

bon

isot

ope

valu

e

78

PAHs-Combined GC and GCIRMSData

Comparison of MT Soil andNAPL CSIR Results

-30.00

-29.00

-28.00

-27.00

-26.00

-25.00

-24.00

-23.00

-22.00

nap mn2mn1

acy

ace dbf flu phe ant fly pyr baa chr

bbkf bapip_d

ba bp

Compound

?13C

(‰)

MT03

MT07MT09MT10MT NAPL

Chlorinated SolventsChlorinated Solvents--SourceSourceStructuresStructures

C C

Cl

Cl

Cl

ClC C

H

Cl

H

Cl

ClCl

C C

Cl

H

Cl

Cl

C C

Cl

H

Cl

H

PCE

TCE

cis-1,2-DCE

1,1,2,2-PCA

C C

Cl

Cl

H

Htrans-1,2-DCE

C C

Cl

H

H

Cl1,1-DCE

Reductivedechlorination

Dechlorination

Dehydrohalogenation

C CCl

Cl

Cl

Cl

C CCl

H

Cl

Cl

C CCl

Cl

H

HC C

Cl

H

Cl

HC C

Cl

H

H

Cl

C CCl

H

H

H

C CH

H

H

H

C CH

H

H

ClClCl

C CH

H

H

HClCl

C CH H

HHCl

C CH

H

H

HHH

C CH

Cl

H

ClClCl

H

Degradation of Chlorinated SolventsDegradation of Chlorinated Solvents

Chlorinated SolventsChlorinated Solvents•• Source differentiation of chlorinatedSource differentiation of chlorinatedsolventssolvents--limited success due to smalllimited success due to smallrange of source values.range of source values.

•• Monitoring naturalMonitoring natural attentuationattentuation ––significant successsignificant success--isotopic enrichmentisotopic enrichment

•• Differentiation ofDifferentiation of abioticabiotic v. bioticv. biotictransformationtransformation--promising laboratorypromising laboratoryresults now being applied to fieldresults now being applied to fieldstudiesstudies

CC--ClCl informationinformation

TCE

-33

-32

-31

-30

-29

-28

-27

-26

-4 -2 0 2 4 6δ37Cl

δ13C

DOW92PPG93ICIStanchemDOW95PPG95

PCE

-40

-35

-30

-25

-20

-15

-10

-5

0

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5δ37Cl

δ13C

DOW92DOW95PPG93PPG95ICI93

Each compound from eachmanufacturer show a specific

isotopic composition on C and Cl.

The variations between yearsare due to changes in theisotopic composition of

products used in the synthesisof PCE and TCE.

The idea was to conduct this kind ofsurvey study with TCE and PCE

coming from different manufacturers(DOW, PPG, ICI)…

From Beneteau et al., 1999; Warmerdarm et al., 1995

TCE Degradation Site Study

Hunkeler et al., J. Contaminant Hydrology, 74, 265-282,2004.

Hunkeler et al., J. Contaminant Hydrology, 74, 265-282,2004.

TCE Degradation Site Study

A

B

C

Other possiblesources?

Source Discrimination of PCE andTCE

Composite plot of all isotope data

-34

-32

-30

-28

-26

-24

-22

-30 -28 -26 -24 -22 -20

TCE

PCE

SwanSwan**2004DimitriMixed2002April 2005May-05

Source B

Source C

Source A

BiodegradationTrend

Source Discrimination of

PCE and TCE

MTBEMTBE•• MTBEMTBE--octane enhancer andoctane enhancer andoxygenateoxygenate

•• MTBE may represent 11MTBE may represent 11--15%15%of gasoline volume in some casesof gasoline volume in some cases

•• MTBE relativelyMTBE relatively calcitrantcalcitrant andandvery water solublevery water soluble

•• Isotopes utilized for monitoringIsotopes utilized for monitoringnatural attenuationnatural attenuation

Comparison of Gasolines by GC

OCH3

CH3

CH3

H3C

Monitored Natural AttenuationMonitored Natural Attenuation

Anaerobic PlumeAnaerobic PlumeNew Jersey, BP siteNew Jersey, BP site

Station

PumpsSource

10Meters

plume footprint,determined bythreshold CH4concentration

Samplingwell

Material formicrocosms

collected

Stable Isotopic FractionationStable Isotopic FractionationRayleigh ModelRayleigh Model

-1 -2 -3 -4

Incr

easing

δ13 C

Nat log of remaining MTBE fraction

δ13Ct = ε* lnF + δ13Co

MTBE concentration decreases

Slope = ε

Intercept = δ13Co

420 ppb10 ppb

-30

-20

-10

0

10

-5-4-3-2-10

MTBE Yr. 1

MTBE Yr. 2

MTBE Yr. 3

LN F MTBE

δ13 C

ε field = -8.1

Anaerobic Plume New Jersey, BPAnaerobic Plume New Jersey, BP

Biodegradation Graph

0

20

40

60

80

100

-35 -25 -15 -5 5 15 25 35δ13C MTBE in-situ

Min

imum

% M

TBE

degr

aded If the observed

δ13C is –18, at

least 50 % of

MTBE has been

degraded in the

sampled volume

(Rayleigh Eqn)

δ13Ct = ε* lnF + δ13Co

Chlorine-Perchlorate

Perchlorate taints water in 22states. Main sources: Militarybases, aerospace installations,and defense contractors thatbuild rockets.A small amount of perchloratepollution in the U.S. is believedto have stemmed from a sodiumnitrate fertilizer made in Chile.

Perchlorate

Studies released last week findingperchlorate in lettuce have focusedattention on a struggle between EPA andthe Pentagon over cleanup standards forthe chemical.Perchlorate—ClO4

–, a component ofsolid rocket fuel—disrupts thyroiduptake of iodine and taints water suppliesin 20 states.

A study sponsored by the Press Enterprise ofRiverside, Calif., found perchlorate ion in all 18samples of lettuce analyzed, and a test sponsoredby the Environmental Working Group (EWG)detected the substance in four of 22 lettucesamples purchased in California. The source isthought to be irrigation water from the lowerColorado River, which carries perchlorate from aformer industrial plant near Las Vegas.

LUBBOCK, TX, Sept. 19 - A toxic component of rocket fuel has been found in supermarket milk at levels exceeding the federal governments currently recommended safe dose (1ppb currently) for drinking water………………………..

TOXIC ROCKET FUEL FOUND IN MILKSAMPLES FROM TEXAS SUPERMARKETS

Are Perchlorate Sources Isotopically Distinct?

-20

-15

-10

-5

0

5

-30 -25 -20 -15 -10 -5 0

δ18O

δ37C

lCsClO4 (2 batches)

NaClO4

NaClO4.H2OKClO4

NaClO4.H2O

Hoffman (fertilizer)

Hoffman-2 (fertilizer) sqm-7791 (Atacama)

AT-74-1 (Atacama)

Edwards AFB groundwater

ANTHROPOGENIC

NATURAL

SummarySummary•• The concept of environmentalThe concept of environmentalforensics is a rapidly expanding.forensics is a rapidly expanding.

•• Conventional analytical techniques suchConventional analytical techniques suchas GC and GCMS are used extensivelyas GC and GCMS are used extensivelybut in some cases provide limitedbut in some cases provide limiteduseful data.useful data.

•• The emergence of GCIRMS has leadThe emergence of GCIRMS has leadto numerous applications for bothto numerous applications for bothsource determinations and, perhapssource determinations and, perhapsmore importantly, monitoring naturalmore importantly, monitoring naturalattenuation.attenuation.