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