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
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
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
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..
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
-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
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..
-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.
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
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
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
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.