THE EMERGENCE OF STABLE ISOTOPES IN ENVIRONMENTAL AND FORENSIC GEOCHEMISTRY STUDIES

Transcription

1 TE EMERGENE OF STABLE ISOTOPES IN ENVIRONMENTAL AND FORENSI GEOEMISTRY STUDIES R. Paul Philp, School of Geology and Geophysics, University of Oklahoma, Norman, OK

2 Forensic Geochemistry Environmental forensic studies generally involve a product, typically organic, released into some type of environment, such as lakes, rivers, oceans, or groundwater. owever with any incident the questions asked are almost always the same.

3 SO WO DID IT? Important questions: What is it? Where did it come from? Who did it? Bottom line: Who is going to pay to clean it up?

4 Forensic Geochemistry Techniques commonly used to answer these questions: Gas hromatography (G) Gas hromatography-mass Spectrometry (GMS)

5 Minutes Fingerprinting by Gas hromatography ondensate JP Minutes Minutes Gasoline Diesel

6 rude Oil hromatogram 17 Pristane Phytane 35 0

7 Processes acting on spilled products

8 Weathering Effects of rude a INITIAL OIL Oils b EVAPORATED OIL c WATER-WASED OIL d BIODEGRADED OIL AFTER 1 MONT e BIODEGRADED OIL AFTER 2 MONTS f BIODEGRADED OIL AFTER 4 MONTS 15

9 STEROL/STERANE BIOMARKERS O STEROL STERANE

10 M/z 217 Sterane hromatogram

11 M/z 191 Terpane hromatogram Tricyclics opanes

12 Biomarker Distributions

13 Forensic Geochemistry G and GMS-powerful, well established, used extensively in litigation. Additional evidence required when G and GMS are of limited, or no, use- (i.e.. single components or refined products.) In these situations stable isotopes are being used to provide additional information.

14 What are Isotopes? Atoms of same element with differing masses; same # of protons, different # of neutrons p e - p n e - p n n e - ydrogen, 1 Lighter Deuterium, 2, D Tritium, 3, T eavier Sum of protons and neutrons is the atomic mass

15 What are Stable Isotopes? arbon exists as two stable isotopes, 12 and 13 which differ in the number of neutrons they contain. 12 has 6 electrons, 6 protons and 6 neutrons; 13 has 7 neutrons. 1 has 1 electron and 1 proton and 2 has 1 electron, 1 proton and 1 neutron.

16 Other Isotopes of Environmental Interest hlorine ( 35 / /24.47) Sulfur ( S/ S-94.02/3.21) Nitrogen ( N/ N-99.64/0.36)

17 Data Output-Isotope Scale R R 1 13 sample = R = 13 / 12 standard 1000 PDB Standard Isotopically lighter Isotopically depleted More negative

18 Forensic Geochemistry Stable isotopes utilized in geochemical applications for more than 50 years.

19 Single omponent ontaminants G-FID or GMS Source A Toluene Source B Toluene When the contaminant is a single componenthow can you distinguish one from another? G and GMS no help. Isotopes may be different

20 Allocation 2 Sources Toluene 13 or 2 : 2 sources, single tracer Source A: Source B: Plume Plume = 80% Source A, 20% Source B

21 Prince William Sound Residues Exxon Valdez Oil

22 Terpanes in Prince William Sound Residues R

23 Forensic Geochemistry More recently the combination of gas chromatography with isotope ratio mass spectrometry (GIRMS) has lead to a significant increase in the number of isotopic applications.

24 Refined Products For example diesel derived from different crude oils can be differentiated using carbon and hydrogen isotopic compositions. Isotope data can be supported by various biomarkers not commonly used in environmental studies: sesquiterpanes; adamantanes; ; and degraded steranes.

25 Diesel Fingerprints

26 Isoprenoid Isotope Fingerprints 14i 15i 16i 18i PR P alifornia Oklahoma arbon Isotope Value

27 Forensic Geochemistry Site A B MW 1 Groundwater flow direction MW6 Site B

28 Weathered and Unweathered Diesel Diesel MW 1 Pr Ph Diesel MW 6 17

29 arbon Isotope Values for Isoprenoids 14i 15i 16i 18i PR P MW 6 MW

30 Adamantanes in Diesel Fuels Diesel MW 1 Diesel MW

31 Gasolines Gasolines from different sources often have very similar chromatograms. Gasolines are devoid of biomarkers, further limiting correlation possibilities. One solution is to use GIRMS for both the hydrocarbons and additives.

32 omparison of Gasolines by G

33 arbon Isotopic omposition of Gasolines from Oklahoma (FOK, GOK) and the East oast (LE, OE) Peak Number ( ) LE OE FOK GOK This figure shows the carbon isotopic fingerprint of gasolines sampled from Oklahoma and from the East oast and demonstrates that these gasolines are significantly different in terms of isotopic composition and can be discriminated from each other on this basis. The peak numbers are identified in the section above.

34 oal Tar-PAs

35 PAs and Stable Isotopes urrent interest is in discriminating PAs derived from former manufactured gas plant (MGP) wastes versus those from general urban background aromatics Urban backgrounds have a fairly narrow range and small differences may be related to source differences

36 PAs-ombined G and GIRMS 08 Data D 16D 24D Peak ID 7 8 arbon isotope value

37 omparison of MT Soil and NAPL SIR Results nap mn2 mn1 acy ace dbf flu phe ant fly pyr baa chr bbkf bap ip_dba bp ompound MT03 MT07 MT09 MT10 MT NAPL?13 ( )

38 hlorinated Solvents hlorinated Solvents-Source Source Structures Structures PE TE cis-1,2-de 1,1,2,2-PA trans-1,2-de 1,1-DE

39 Reductive dechlorination Dechlorination Dehydrohalogenation Degradation of hlorinated Solvents Degradation of hlorinated Solvents

40 hlorinated Solvents Source differentiation of chlorinated solvents-limited limited success due to small range of source values. Monitoring natural attentuation significant success-isotopic enrichment Differentiation of abiotic v. biotic transformation-promising laboratory results now being applied to field studies

41 - information TE DOW92 PPG93 II Stanchem DOW95 PPG95 Each compound from each manufacturer show a specific isotopic composition on and. The variations between years are due to changes in the isotopic composition of products used in the synthesis of PE and TE. The idea was to conduct this kind of survey study with TE and PE coming from different manufacturers (DOW, PPG, II) PE DOW92 DOW95 PPG93 PPG95 II93 From Beneteau et al., 1999; Warmerdarm et al., 1995

42 TE Degradation Site Study unkeler et al., J. ontaminant ydrology, 74, ,2004.

43 TE Degradation Site Study unkeler et al., J. ontaminant ydrology, 74, ,2004.

44 Source Discrimination of PE TE and B A Other possible sources?

45 Source Discrimination of PE and TE omposite plot of all isotope data Source B -26 Swan Swan** PE Biodegradation Trend 2004 Dimitri Mixed2002 April Source A Source May TE

46 MTBE MTBE-octane enhancer and oxygenate MTBE may represent 11-15% 15% of gasoline volume in some cases MTBE relatively calcitrant and very water soluble Isotopes utilized for monitoring natural attenuation

47 omparison of Gasolines by G O 3

48 Monitored Natural Attenuation

49

50 Anaerobic Plume New Jersey, BP site Material for microcosms collected plume footprint, determined by threshold 4 concentration 10 Meters Pumps Source Station Sampling well

51 Stable Isotopic Fractionation Rayleigh Model Increasing 13 Intercept = 13 o Nat log of remaining MTBE fraction MTBE concentration decreases Slope = 13 t = * lnf + 13 o

52 Anaerobic Plume New Jersey, BP ppb 10 ppb -20 field = -8.1 MTBE Yr. 1 MTBE Yr. 2 MTBE Yr LN F MTBE

53 Biodegradation Graph Minimum % MTBE degraded MTBE in-situ If the observed 13 is 18, at least 50 % of MTBE has been degraded in the sampled volume (Rayleigh Eqn) 13 t = * lnf + 13 o

54 hlorine-perchlorate

55 Perchlorate Perchlorate taints water in 22 states. Main sources: Military bases, aerospace installations, and defense contractors that build rockets. A small amount of perchlorate pollution in the U.S. is believed to have stemmed from a sodium nitrate fertilizer made in hile.

56 TOXI ROKET FUEL FOUND IN MILK SAMPLES FROM TEXAS SUPERMARKETS Studies released last week finding perchlorate in lettuce have focused attention on a struggle between EPA and the Pentagon over cleanup standards for the chemical. Perchlorate O 4, a component of solid rocket fuel disrupts thyroid uptake of iodine and taints water supplies in 20 states. A study sponsored by the Press Enterprise of Riverside, alif., found perchlorate ion in all 18 samples of lettuce analyzed, and a test sponsored by the Environmental Working Group (EWG) detected the substance in four of 22 lettuce samples purchased in alifornia. The source is thought to be irrigation water from the lower olorado River, which carries perchlorate from a former industrial plant near Las Vegas. LUBBOK, TX, Sept 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..

57 Are Perchlorate Sources Isotopically Distinct? 5 0 ANTROPOGENI KO 4 so 4 (2 batches) NaO 4. 2 O NaO 4 Edwards AFB groundwater -5 NaO 4. 2 O offman (fertilizer) AT-74-1 (Atacama) -15 offman-2 (fertilizer) sqm-7791 (Atacama) NATURAL O

58 Summary The concept of environmental forensics is a rapidly expanding. onventional analytical techniques such as G and GMS are used extensively but in some cases provide limited useful data. The emergence of GIRMS has lead to numerous applications for both source determinations and, perhaps more importantly, monitoring natural attenuation.