Torsten C. SchmidtTorsten C. Schmidt
StableStable Isotope Analysis in Isotope Analysis in WaterWaterScience: A Science: A PowerfulPowerful Tool to Tool to Track Track SourcesSources of Pollutionof Pollution
Department of ChemistryChair of Instrumental Analysis
OutlineOutline
Introduction: a few highlights
Use of isotope variation
Case Study 1: Nitrate in groundwater
Case Study 2: Chlorinated hydrocarbons in groundwaterSourcesFate
Conclusions
Analytical Analytical Information Information from from a a SampleSample
Identification: What?
Quantification: How much?
Analysis of isotope composition:Source? Fate?
Doping Doping ControlControl: : Steroid AbuseSteroid Abuse
Date courtesy of Francois Fourel, GV Instruments
Authenticity Authenticity ControlControl: : OriginOrigin of White of White Wine Wine
Data courtesy of Dr Ian Begley (Iso-Analytical, UK)
Source AllocationSource Allocation of of ContaminantsContaminants
Erika oil spill 1999: Did it cause oiling of birds (300000 killed)?Ref.: Mazeas and Budzinski (2002), Environ. Sci. Technol. 36, 130
Erika OilNorth Atlantic
Arcachon Bay
Bird Feathers
Crohot
NaturalNatural Isotope VariationIsotope Variation
12C 98.9 %
13C 1.11 %
1000⋅⎟⎟⎠
⎞⎜⎜⎝
⎛ −=
reference
referencesamplex R
RRδ
R = ratio of heavy to light isotope (e.g., 13C/12C)
[‰]
Reference
Compound
ImportantImportant Stable Isotopes in Stable Isotopes in NatureNature
Stable Isotopes
Natural abundance heavier isotope [%]
2H / 1H 0.01557
13C / 12C 1.11140
15N / 14N 0.36630
18O / 16O 0.20004
34S / 32S 4.21500
Here is the information we are looking for in stable isotope analysis
CSIA CSIA PrinciplePrinciple ((CarbonCarbon))
Environmental ForensicsEnvironmental Forensics: : Source AllocationSource Allocation of of CompoundsCompounds
Prerequisites:• Isotope composition of various sources differs• Isotope composition is stable
Adapted from: S. A. Stout et al., ES&T 32 (1998), 260A
The Nitrate DilemmaThe Nitrate Dilemma
Use of nitrate to improve agricultural yields, BUT:
Adverse effects including
Methemoglobinemia = “blue baby syndrome”
Eutrophication of lakes and rivers
Groundwater pollution (current limit EU: 50 mg/L)
Remediation hardly feasible
MajorMajor SourcesSources of Nitrateof Nitrate
Animal manure spreading
Sewage effluentFertilizers
The Alsace aquiferThe Alsace aquifer
Strasbourg
• Sedimentary rocks.• NO3 close to 50 mg L-1.• No natural denitrification.
Data courtesy of Dr. David Widory, BRGM
Pollution Sources:Pollution Sources:Isotopic CharacterizationIsotopic Characterization
Widory et al. (2004), J. Contam. Hydrol. 72, 165
δ15N mainly discriminates fertilizers from sewage and animal manure.
δ11B mainly discriminates animal manure from sewage and fertilizers.
Non-pollutedend-member
Results: Nitrogen IsotopesResults: Nitrogen Isotopes
• One non-polluted end-member.
• No natural denitrificationso nitrogen is controlled by mixing processes.
• Identification of at least 2 pollution sources.
Data courtesy of Dr. David Widory, BRGM
Results: Boron IsotopesResults: Boron Isotopes
• Same non-polluted end-member.
• Identification of at least 2 pollution sources.
Data courtesy of Dr. David Widory, BRGM
DualDual--Isotope ApproachIsotope Approach
Data courtesy of Dr. David Widory, BRGM
Further Isotope OpportunitiesFurther Isotope Opportunities
Data courtesy of Dr. Carol Kendall, USGS
Hydrocarbons
Other organic compounds 1.0 %
Non-classified 4.5 %
Heavy Metals 1.0%Other inorganics 0.4%
8.0%
20.3%
64.8%
After LfU, Baden-Wuerttemberg, 1996
Chlorinated Hydrocarbons Mono- and Polycyclic Aromatic Hydrocarbons
Important Important PointPoint--Source Source Groundwater ContaminantsGroundwater Contaminants
Isotope Isotope SignaturesSignatures of Industrial of Industrial Chlorinated HydrocarbonsChlorinated Hydrocarbons
After Warmerdam, E. M. v et al. (1995), Applied Geochemistry 10, 547
ClCl
Cl Cl
HCl
Cl Cl
Cl
Cl
Cl
PCE
TCE
TCA
Degradation of Degradation of ChlorinatedChlorinatedEthenesEthenes
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
ClCl
Cl
Cl
Cl
Vinylchloride (VC)
1,1-DCE cis-DCE trans-DCE
Perchloroethene (PCE)
Trichloroethene (TCE)
strongly anoxic only
anaerobic and aerobic conditions
anaerobic and aerobic conditions
Chlorinated Hydrocarbons Chlorinated Hydrocarbons at a at a ComplexComplex Industrial SiteIndustrial Site
Stuttgart Zoo
Primary Contamination
Secondary Contamination
Chlorinated Hydrocarbons Chlorinated Hydrocarbons at a at a ComplexComplex Industrial SiteIndustrial Site
Problems: • Fractured rock system with preferential flow• Multiple sources possible
Total CHC conc.:< LOD< 0.01 mg/L (guideline value)0.01-0.10.1-1> 1not investigated
Chlorinated HydrocarbonsChlorinated Hydrocarbons at a at a ComplexComplex Industrial SiteIndustrial Site
Total CHC conc.:< LOD< 0.01 mg/L (guideline value)0.01-0.10.1-1> 1not investigated
Constant Source Signature Constant Source Signature Epple?Epple?
Slightly anaerobic, PCE: -26.8 ‰
Aerobic, PCE: -24.0 ‰
Total CHC conc.:< LOD< 0.01 mg/L (guideline value)0.01-0.10.1-1> 1not investigated
Contribution FumyContribution Fumy??
Strongly anaerobic, PCE: -23.4 ‰, heavily degraded, accumulation of DCE and VC
Aerobic, PCE: -24.0 ‰
Total CHC conc.:< LOD< 0.01 mg/L (guideline value)0.01-0.10.1-1> 1not investigated
Separate Separate Source forSource for Northern Northern Plume BoundaryPlume Boundary??
Aerobic, PCE: -24.4 ‰
Total CHC conc.:< LOD< 0.01 mg/L (guideline value)0.01-0.10.1-1> 1not investigated
Separate Separate Source for Source for Southern Southern Plume BoundaryPlume Boundary??
Aerobic, constant source signature PCE: -27.5 ‰TCE, DCE further degraded (up to + 15 ‰)
Total CHC conc.:< LOD< 0.01 mg/L (guideline value)0.01-0.10.1-1> 1not investigated
SummarySummary SourcesSources
Fundamentals of Isotope Fundamentals of Isotope FractionationFractionation
Difference of bond strength between light and heavy isotopes leads to fractionation
12C 13C
12C 12C
13C 13C
Quantification Quantification of Biodegradation of Biodegradation Southern Southern PlumePlume
-30-25-20-15-10-505101520
050100150200250300
CHC Conc. in µg/L
δ13
C in
per
mil
PCETCEcis-DCE
Quantification Quantification of Biodegradationof BiodegradationSouthern Southern PlumePlume
y = -9.0x - 20.7R2 = 0.9684
y = -20.1x - 9.2R2 = 0.9103
-25-20-15-10-505101520
-2.5-2-1.5-1-0.50
ln C/C0
δ13
C in
per
mil
TCEcis-DCELinear (cis-DCE)Linear (TCE)
Reported ε for anaerobic TCE degradation: -4 to -14 (Hunkeler 2005)aerobic TCE degradation: -18.2 to -20.7 (Barth 2002)
AssesmentAssesment of of transformation transformation reactionsreactions: 2D: 2D--Isotope AnalysisIsotope Analysis
Isotopic shifts during aerobic degradation of benzene by two different bacteria
Ref.: Hunkeler et al. (2001), Environ. Sci. Technol. 35, 3462
TakeTake--Home MessagesHome Messages
Isotope analysis provides unique information that you CANNOT achieve with other kinds of instrumental analysis
Environmental investigations without isotope analysis will often miss crucial information or are less cost-effective
Isotope analysis is ONE powerful tool in your toolbox, oftenMULTIPLE lines of evidence are necessary
Some isotope analyses nowadays can be performed on a routine base – but there is much more still to develop
AcknowledgementsAcknowledgementsEAWAG/ETH Zurich (CH)
Michael BergLuc Zwank
Center for Applied Geoscience, University Tuebingen (D)
Michaela BlessingMaik Jochmann
BRGM, Orleans (F)David Widory
Department of ChemistryChair of Instrumental Analysis
Department of ChemistryChair of Instrumental Analysis
Thanks for your attentionThanks for your attention!!
AssessmentAssessment of of degradation degradation reactionsreactions
Prerequisite:Isotope composition changes over course of reaction
Elements Elements measuredmeasured onlineonline
Stable Isotopes
Natural abundance of heavier isotope [%]
Conversion gas
Measured m/z
D/H 0.015 H2 2,3
13C/12C 1.11 CO2 44, 45, 46
15N/14N 0.366 N2 28, 29, 30
18O/16O 0.204 CO 28, 30
Further Isotope OpportunitiesFurther Isotope Opportunities
Data courtesy of Dr. David Widory, BRGM
Compound On Column [μg/L]
SPME [μg/L]
P&T [μg/L]
trans-1,2-dichloroethene 75’000 130 1.5
cis-1,2-dichloroethene 71’000 92 1.1 trichloroethene 84’000 94 1.4 tetrachloroethene 74’000 66 2.2 methyl tert-butyl ether 24’000 16 0.6 benzene 19’000 22 0.3 toluene 9’000 9 0.2
CSIA CSIA DetectionDetection Limits Limits for for VOCVOC
=> Improved detection limits of online P&T-GC/IRMS open new fields of applications for CSIA
Zwank, Berg, Schmidt, Haderlein (2003), Anal. Chem. 75, 5575
Why not usingWhy not using GCGC--MS?MS?
=> Only possible with simultaneous measurement of ion current ratios on fixed collectors
Example: δ13C value of compound X: +10 ‰, -> Isotope ratio 1 % higher than that of internat. standard
VPDB: 13C/12C = 0.011180X: 13C/12C = 0.011292
Small natural variation of isotope composition require very high precision
That‘s where the information is
ExampleExample 2: 2: Methyl Methyl terttert--butylbutyl Ether (MTBE)Ether (MTBE)
Used as oxygenate in gasoline (up to 15 % Vol.)
High production volume chemical (ca 20 Mio tons/year)
High aqueous solubility (ca. 50 g/L) + limited degradability
=> High groundwater pollution potential
Field Field Site: MTBE Site: MTBE DisposalDisposal SiteSite
MTBE Removal: MTBE Removal: Possible Possible ProcessesProcesses
FieldField Site: MTBE Isotope Site: MTBE Isotope DataData
Zwank, Berg, Elsner, Schmidt, Schwarzenbach, Haderlein (2005), Environ. Sci. Technol., in press
Hydrogen Fractionation Hydrogen Fractionation vs. vs. Relative Relative ConcentrationConcentration of MTBEof MTBE
Literature:
Aerobic: -29 to -66 ‰
Anaerobic: -11.5 ‰
Zwank, Berg, Elsner, Schmidt, Schwarzenbach, Haderlein (2005), Environ. Sci. Technol., in press
Possible Reaction Mechanisms Possible Reaction Mechanisms of MTBE Degradation of MTBE Degradation
Zwank, Berg, Elsner, Schmidt, Schwarzenbach, Haderlein (2005), Environ. Sci. Technol., in press
DecipheringDeciphering MTBE Degradation: MTBE Degradation: Using KineticUsing Kinetic Isotope Isotope EffectsEffects
Expected 13C KIE
1 1.02 1.04 1.06 1.08 1.1
Oxidation
SN2
SN1
Expected 2H KIE
1 1.5 2 2.5 3 3.5
Oxidation
SN2
SN1
Observed KIEs1.05 1.05
=> SN2 mechanism most likely anaerobic transformation pathway
Zwank, Berg, Elsner, Schmidt, Schwarzenbach, Haderlein (2005), Environ. Sci. Technol., in press