1. Chemical Fingerprinting of Groundwater Plumes: Concepts and Case Studies David S. Lipson, CPG Blasland, Bouck & Lee, Inc. Golden, CO

2. Premise Sources of chemicals impart unique physical- chemical characteristics (also known as “fingerprints”) on the chemicals. When chemicals are released and contaminate environments (e.g., air, groundwater), their fingerprints can be used to help establish the timing of the release and allocate between different sources in many cases.

3. Outline Situations where chemical fingerprinting of groundwater plumes may be useful Fingerprinting methods: 1.Concentration ratios 2.Isotopes 3.Single, or unique chemicals Strengths and weaknesses Case studies

4. One Situation Where Fingerprinting May Be Useful: Co-Mingled Plumes From Multiple Sources Oil Terminal A Oil Terminal B Oil Terminal C Pipelines

5. A Second Situation Where Fingerprinting May Be Useful: Co-Mingled Plume From A Single Source 60s Release Big Defense Contractor Late 70’s Release Ongoing Release From Mid-80s

6. Chemical Concentration Ratios Used when chemical mixtures are present in a plume, which includes most contaminant plumes of interest. Most chemical sources involve mixtures. For example: –Gasoline and other petroleum fuels (100s of compounds) –Coal tar and creosote (100s of compounds) –Solvents (multiple solvents often used) –Acid mine drainage (multiple metals often present) –Dielectric fluids (PCBs are mixtures of many congeners) It is rare when a single chemical is released to the environment due to widespread use of chemical mixtures, chemical additives, and impurities. Even if a single chemical were released to the environment, in many cases chemicals degrade forming intermediate byproducts that add to the chemical mixture.

7. Chemical Concentration Ratios: Transport of a Two-Component Solvent Mixture 0 feet 500 feet1000 feet 1500 feet 2000 feet 3000 feet 4000 feet 5000 feet 6000 feet

8. Conclusion: Fingerprint changes with time and distance due to degradation 0 feet250 feet500 feet750 feet1000 feet 1500 feet2000 feet2500 feet3000 feet Chemical Concentration Ratios: Transport of a Three-Component Solvent Mixture

9. State of Arkansas vs. Diamond Lakes Oil Co.

10. MW5-5R Diamond Lakes Oil Co. (Station A) Station B GW Flow Direction Contaminated Residence

11. Ternary Diagram Showing Concentration Ratios of Benzene, Toluene, and Xylenes From All Groundwater Samples Collected at Station A and Station B Monitor Wells 50 100 % Benzene 100% Xylenes 100% Toluene 25 MW-5/5R Station A Groundwater Samples (N = 121) Station B Groundwater Samples (N = 62) Fresh Gasoline

12. 100% Toluene100% Xylenes 100% Benzene 50 E H M F N L K 1 2 3 4 5 6 25 < 1 ppm 1 - 10 ppm > 10 ppm Circle Size Indicates Total BTX Concentration Station A Groundwater Samples (N = 11; non-detects not shown) Station B Groundwater Samples (N = 6) J 2 Ternary Diagram Showing BTX Concentration Ratios - June 1998 Data Fresh Gasoline

13. 100% Toluene 100% Xylenes 100% Benzene 50 Circle Size Indicates Total BTX Concentration < 1 ppm 1 - 10 ppm > 10 ppm Station A Groundwater Samples (N = 11) Station B Groundwater Samples (N = 6) D E F H I J K L M N O 1 2 3 4 5 6 25 Ternary Diagram Showing BTX Concentration Ratios - June 1999 Data Fresh Gasoline

14. 100% Benzene 50 Circle Size Indicates Total BTX Concentration < 1 ppm 1 - 10 ppm > 10 ppm Station A Groundwater Samples (N = 11) Station B Groundwater Samples (N = 6) H D E F K M L I J N O 1 2 3 4 5 6 25 100% Toluene 100% Xylenes Ternary Diagram Showing BTX Concentration Ratios - August 1999 Data Fresh Gasoline

15. 100% Toluene100 % Xylenes 100 % Benzene 50 Circle Size Indicates Total BTX Concentration < 1 ppm 1 - 10 ppm > 10 ppm Station B groundwater samples from MW-5/MW-5R 50 1/99 8/00 6/98 4/99 8/99 6/99 12/99 6/00 2/00 4/00 25 UST Excavation (Station B) Ternary Diagram Showing BTX Concentration Ratios – MW5/MW-5R With Time Fresh Gasoline

16. State of Arkansas vs. Diamond Lakes Oil Co. Findings of the Case: Concentration ratios demonstrated that gasoline chemicals from Station B had a fingerprint different than gasoline chemicals from Station A. The BTX concentration ratios also showed that fresh releases (slugs) of gasoline were emanating from Station B. The jury found in Station A’s favor, awarding damages of $300,000. The ruling, and expert testimony, survived on appeal to the Supreme Court of Arkansas.

17. Chemical Isotopes Nuclear Structure of Atoms: Protons and neutrons Protons = atomic number Protons + neutrons = atomic weight Isotopes: Different forms of the same element that have the same atomic number but different molecular weights. Example: Oxygen Most oxygen atoms have 8 protons and 8 neutrons Atomic weight 16: 16 O About 0.2% of oxygen atoms have 10 neutrons Atomic weight 18: 18 O About 0.04% of oxygen atoms have 9 neutrons Atomic weight 17: 17 O

18. Molecular weight is important in environmental studies because it influences the fate and transport of chemicals Example: Evaporation of water Chemical Isotopes

20. Stable chemical isotopes useful in environmental forensics: ChemicalIsotope RatioNatural Abundance (%) Carbon 13 C 13 C / 12 C 1.11 Hydrogen 2 H 2 H / 1 H 0.015 Oxygen 18 O 18 O / 16 O 0.204 Chlorine 37 Cl 37 Cl / 35 Cl24.23 Sulfur 34 S 34 S / 32 S 4.21 Bromine 81 Br 81 Br / 79 Br 49.31 There are numerous other isotopes that exist, and can be evaluated depending on the site-specific application.

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22. Chemical Isotopes Because isotopes have different molecular weights, certain processes can select for different isotopes. Examples: Evaporation selects for lighter isotopes, resulting in heavier residue. Biodegradation reactions select lighter isotopes, resulting in heavier residue. Chemical manufacturing processes can select for different isotopes Therefore, these processes can impart a unique isotopic fingerprint to a chemical plume undergoing transport and degradation in the environment.

23. Standard analytical methods (e.g., GC-IRMS) allow compound-specific detection of isotopes at ppm and ppb levels. Applications: Fingerprint hydrocarbons and solvents Identify/allocate sources of pollution Examine fate and transport processes Evaluate remedial measures Forensic Isotope Geochemistry

24. Crude Oil and Refined Products

25. BTEX in Gasoline Samples

26. Chlorinated Solvents -32 -31 -30 -29 -28 -27 -26 -25 -4-3-2012345  37 Cl (per mil)  13 C (per mil) TCE TCA Isotopic composition of solvents from different manufacturers Adapted from Shouakar-Stash et al. (2003)

27. TCE  13 C or  37 Cl, 2 sources, single tracer Source B:  13 C -25‰  37 Cl +3‰ Source A:  13 C -30‰  37 Cl -2‰ Plume  13 C -29‰  37 Cl -1‰ Plume = 80% Source A, 20% Source B Allocation – 2 Sources

28. Single, or Unique Chemicals That Can Be Used to Fingerprint Plumes in Some Cases Gasoline Additives Methyl tertiary butyl ether (MTBE) Tertiary butyl alcohol (TBA) Lead anti-knocks (e.g., tetraethyl lead) Talloamines 1,2-Dichloroethane (DCA) Solvent stabilizers 1,4-Dioxane Dimethyl amine (DMA) Tetrahydrofuran (THF) Others: chrome, nickel, copper

29. Strengths and Weaknesses Of These Plume Fingerprinting Methods  Demonstrative  Strong visual impact  Easily explained  Proven in court  Powerful if conditions permit  Excellent where there are distinct differences in compounds  Demonstrative  Powerful where present  Concentration Ratios  Isotopic Analysis  Unique Chemicals Subject to misapplication Success is site-specific Data do not always exist Subject to misapplication & faulty interpretation Weathering of compounds can limit viability Success is site-specific Data do not always exist Strengths Weaknesses

30. Conclusions The state of the science has progressed significantly in the past several years to permit fingerprinting of contamination plumes in many cases. There are several, proven plume fingerprinting methods that can be used. Multiple lines of evidence supporting the same conclusion provides the strongest position.