Toluene in Peatlands and Wetlands Mary Mayes and Sheila Luther October 2015

Transcription

1 Toluene in Peatlands and Wetlands Mary Mayes and Sheila Luther October 2015 Matrix Solutions Inc. 1

2 Overview Peatland and wetland characteristics Reason for studies Sources of petrogenic and biogenic toluene in the environment Proposed forensic approach Case studies Next steps and conclusions Matrix Solutions Inc. 2

3 Peatlands and Wetlands Highly saturated (> 75% moisture) High in organic matter and biogenic hydrocarbons are common Sensitive ecosystem Peat-forming wetlands can take up to 10,000 years to form, so reducing the disturbance in these areas is important. Cost of remediation high, both financially and environmentally. Matrix Solutions Inc. 3

4 Why did Matrix do these studies? Toluene measured at concentrations greater than guidelines in soil and water from peatlands and wetlands Areas of potential impact extended off-lease into undisturbed areas Matrix Solutions Inc. 4

5 Literature Search - Sources of Toluene Petrogenic Deep subsurface - Petroleum generation Biogenic Surface and near-surface - Plant growth (atmosphere) - Microbial metabolism (hydrosphere) Pyrogenic Thermal - Combustion of organic matter Ambient - Combustion of fuels from urban areas Matrix Solutions Inc. 5

6 Literature Search - Sources of Biogenic Toluene Plant Growth Toluene emitted to atmosphere by plants under stress New England study demonstrates that summer pattern of atmospheric toluene does not follow benzene Biogenic toluene up to 7% of total toluene measured in air Microbial Metabolism A bacterium isolated from anoxic lake waters produces toluene from phenyl precursor Biogenic toluene documented in sludge bioreactor Matrix Solutions Inc. 6

7 Routine Analytical Approach Analysis of BTEX, F1 using GC/MS in selective ion mode Analysis of F2 to F4 PHCs using GC/FID Method also extracts biogenic organic compounds (BOCs) Soil extract subjected to silica gel clean-up to remove contribution from biogenic hydrocarbons present in organic soils Matrix Solutions Inc. 7

8 New Approach Needed Contacted lab: Was there a way to determine if the toluene measured in samples is biogenic or petrogenic? Could they come up with an analytical approach to solve the problem? Matrix Solutions Inc. 8

9 Forensic Approaches Forensic approaches to date most forensic approaches look only at extractable hydrocarbons Forensic approach taken for this work In conjunction with an extractable hydrocarbon evaluation, applied a forensic approach looking at the volatile organic carbon (VOC) fraction C13:C12 isotope characterization Matrix Solutions Inc. 9

10 Determination of True Biogenic Samples - F3 Fraction Obvious unresolved complex mixture (UCM) present Largest n-alkane within C13-C18 True Biogenic Yes All false? One or more are true? Yes Petrogenic Impact Elevated sulphur C10-C19 alkanes with Carbon Preference Index (CPI) ~1 or C19-C32 alkanes with CPI ~1 Matrix Solutions Inc. Adapted from Harris and Bright

11 Pre-screening Pre-screening requires chromatogram interpretation expertise Does the contamination source have an F2:F3b ratio of 0.10? Yes No Do not proceed with evaluation Does the GC-FID pattern in the peat sample match the GC-FID pattern(s) in the contamination source and/or background soil? No Exclude sample from evaluation Yes Tier 1 Evaluation Do the F2 and/or F4 concentrations in the soil sample exceed soil standards? No Does the F3 concentration in the soil sample exceed the soil standard? No Management not required Yes Management required Yes Tier 2 Evaluation Is the F2:F3b ratio in the soil sample 0.10? Yes No Management not required Decision Process for Biogenic F3 Encountered in Organic Soil Does the soil sample biomarker and/or PAH analysis indicate PHC presence? Yes Management required No Management not required Matrix Solutions Inc. Adapted from Kelly-Hooper et al

12 Proposed Decision Process for Biogenic Toluene Process indicates petrogenic? If F2 to F4 exceedances use Harris and Bright (2006) and/or Kelly Hooper et al. (2013) processes Process indicates biogenic? Petrogenic Impact True Petrogenic markers present? VOC markers Biogenic organic compounds (BOCs) present? Petrogenic markers absent or trace? True True Biogenic Conclusions need to be consistent with field observations True For selected samples and only if required for burden of proof True Matches contaminated source? Isotopic carbon δc13 analysis Matches biogenic material? Requires specialized testing lab services Matrix Solutions Inc. 12

13 Carbon Isotopes Isotopes: atoms of the same element with different amount of neutrons, but equal number of protons in their nuclei Carbon isotopes include: C12 stable and predominant C13 stable C14 radioisotope The approximate ratio of C13 to C12 is 1:99 Matrix Solutions Inc. 13

14 Carbon Isotope Analysis Analysis of stable isotopes for specific compounds is done by Isotope Ratio, Mass Spectrometer (IRMS) known as Compound Specific Isotope Analysis (CSIA) Results expressed relative to a benchmark standard of C13 Matrix Solutions Inc. 14

15 Case Study Applications Selected sites that had the following: Toluene in organic soils from remedial excavations Toluene measured in soil and surface water from peatlands and wetlands from undisturbed areas In collaboration with local laboratories, tested analytical process to distinguish between petrogenic and biogenic toluene Case Study 1 Peatland Case Study 2 Boreal Forest Wetlands Matrix Solutions Inc. 15

16 Case Study 1: Assessment, delineation and remediation of hydrocarbon impacts within peatlands at an abandoned well site Matrix Solutions Inc. 16 NE

17 Site Plan Matrix Solutions Inc. 17

18 West East Cross Section Clay Pad Silty Clay Organic Sump Mix Zone Weathered Sandstone Matrix Solutions Inc. 18

19 Soil Quality Results Toluene, LEPH, HEPH (Background) Xylenes, VPH, LEPH, Benzene, Toluene, LEPH, HEPH Benzene, Toluene Matrix Solutions Inc. 19

20 Soil Quality Results Contaminants of concern benzene toluene LEPH (C 10 -C 19 ) HEPH (C 19 -C 32+ ) Toluene concentration range 1 to 22.8 mg/kg Extent of impact large if lab results were used as received (no interpretation) Matrix Solutions Inc. 20

21 Soil Quality Results Contaminants of concern benzene toluene LEPH (C 10 -C 19 ) HEPH (C 19 -C 32+ ) Offsite Toluene Impacted Area Toluene concentration range 1 to 22.8 mg/kg Extent of impact large if lab results were used as received (no interpretation) Matrix Solutions Inc. 21

22 Soil Quality Results Contaminant of concern benzene Extent of impact much smaller Minimizes disturbance to sensitive undisturbed peat land Matrix Solutions Inc. 22

23 VOC scan Petrogenic Markers Petrogenic Markers m, p-xylenes C3-benzenes ethyl toluenes other aromatic hydrocarbons Matrix Solutions Inc. 23

24 VOC Biogenic Markers Toluene major VOC detected Matrix Solutions Inc. 24

25 VOC Biogenic Markers VOC Scans Example Biogenic Markers camphene pinene carene Matrix Solutions Inc. 25

26 Case Study 1 Carbon Isotopes Petrogenic Flare Pit -20 Refined Gasoline or Crude δc13 toluene signature in petrogenic source range from -22 to Petrogenic Toluene Spikes -30 δc13 Peatlands and Wetlands Suspected Biogenic Toluene -35 Biogenic -40 Matrix Solutions Inc. 26

27 Case Study 2: Background Wetlands Study Former Gas Plant and Active Compressor Station in green zone, west Alberta Gas Plant (south part of site) is part of a regulatory decommissioning project as per the EPEA Approval requirements Decade-long soil remedial program nearly complete Surface water monitoring program at site (9 locations) Matrix Solutions Inc. 27

28 Site Wetlands Monitoring Applied Environmental Quality Guidelines for Alberta Surface Waters (ESRD 2014) Regulatory exceedances encountered: Acidic ph (one location) Toluene (five locations) Total metals As, Cd, Cr, Co, Cu, Pb, Ag, Zn Dissolved metals Al, Fe Question: Are exceedances natural or introduced? Matrix Solutions Inc. 28

29 Marsh Deciduous Swamp Toluene Site Surface Water Monitoring Matrix Solutions Inc. 29

30 Background Wetland Study 15 sites from area sampled Sites classified by Alberta Wetland Inventory classification system Matrix Solutions Inc. 30

31 Background Wetland Study - Methods Field Wetland descriptions and classification In situ water chemistry (temperature, disssolved oxygen, ph, conductivity and turbidity) Lab Analysis Routine chemistry Dissolved hydrocarbons by headspace analysis 5 of 15 samples had detectable toluene These 5 samples - open scan purge and trap dissolved hydrocarbon analysis including full VOC scan 1 of the 5 samples submitted for toluene carbon isotope analysis Matrix Solutions Inc. 31

32 Background Wetlands Study - Results Marsh Deciduous Swamp Shallow Open Water Toluene Matrix Solutions Inc. 32

33 Toluene Concentration (mg/l) Toluene Concentrations at Site and Background Surface Water Active Site Deciduous Swamp Active Site Marsh Background Deciduous Swamp Background Marsh Background Shallow Open Water Linear (Aquatic Life Guideline) Toluene Aquatic Life Guideline: mg/l Sample Series Matrix Solutions Inc. 33

34 Results (cont.) VOC chromatograms indicated both compounds understood to be biogenic (BOCs) and those potentially anthropogenic (?) toluene (?) hexanal (BOC) heptanal (BOC) trimethylbenzene (?) 3-octanone (BOC) o/m/p-cymene (BOC) eucalyptol (BOC) Matrix Solutions Inc. 34

35 VOCs Biogenic Markers VOC Scan Example Biogenic Markers Hexanal O/M/P Cymene Eucalyptol spiking solution contains: nc6, benzene, toluene, ethylbenzene and xylenes Toluene Spike Sample + Spike Abundance Toluene Hexanal O/M/P - Cymene Eucalyptol Sample Blank Time Matrix Solutions Inc. 35

36 Case Study 2 Carbon Isotope Result Petrogenic Flare Pit -20 Refined Gasoline or Crude δc13 toluene signature in petrogenic source range from -22 to Petrogenic Toluene Spikes -30 δc13 Peatlands and Wetlands Suspected Biogenic Toluene Case Study 2 Result -35 Biogenic -40 Matrix Solutions Inc. 36

37 Proposed Decision Process for Biogenic Toluene Process indicates petrogenic? If F2 to F4 exceedances use Harris and Bright (2006) and/or Kelly Hooper et al. (2013) processes Process indicates biogenic? Petrogenic Impact True Petrogenic markers present? VOC markers Biogenic organic compounds (BOCs) present? Petrogenic markers absent or trace? True True Biogenic Conclusions need to be consistent with field observations True Matches contaminated source? Isotopic carbon δc13 analysis For selected samples and only if required for burden of proof Matches biogenic material? True Both case studies were able to establish presence of true biogenic toluene Matrix Solutions Inc. 37

38 Challenges Presence of both petrogenic and biogenic markers More work is required to develop approaches for addressing this Need better characterization of source and background materials Lab analysis packages for biogenic toluene evaluations are needed Matrix Solutions Inc. 38

39 Conclusions If you are doing work in peatlands and wetlands, and suspect that you need to do these evaluations: Need extra sample bottles Always run two or more background samples in open scan mode to determine biomarkers for your site In BC, you should also do silica gel clean up for extractable hydrocarbons (done automatically in Alberta) If you anticipate needing additional evidence (i.e. biomarkers, carbon isotopes) plan in advance Use targeted analyses for characterization - no need to analyze all samples Talk to the lab in advance Matrix Solutions Inc. 39

40 Thank You Exova Maxxam Apache Further information: Sheila Luther Mary Mayes Matrix Solutions Inc. 40

41 References Faubert, P. et al Non-methane Biogenic Volatile Organic Compound Emissions From A Subarctic Peatland Under Enhanced UV-B Radiation. Ecosystems 13, p Fischer-Romero, B. et al., Tolumonas auensis gen. nov., sp. nov., a toluene-producing bacterium from anoxic sediments of a freshwater lake. Int. J. Syst. Bact., 46(1), Guenther, A Biological and Chemical Diversity of Biogenic Volatile Organic Emission In The Atmosphere. ISRN Atmos. Sciences, Article ID , Hindawi Publishing Corp. 27 p. Harris, C. and Bright, D., Hydrocarbon Delineation in Muskeg: Distinguishing Biogenic from Petrogenic Sources. AECOM and UMA Engineering Ltd. Presented at ESSA RemTech Symposium, Banff Alberta. Heiden, A.C. et al Toluene Emissions from Plants. Geoph. Res. Let., 26(9), p Jüttner, F. and Henatsch, J.J., Anoxic hypolimnion is a significant source of biogenic toluene. Nature, 323, Matrix Solutions Inc. 41

42 References Kelly-Hooper, F., Farewell, A.J., Pike, G., Kennedy, J., Wang, Z., Grunsky, E.C., and Dixon, D.G Is it Clean or Contaminated Soil? Using Petrogenic Versus Biogenic GC-FID Chromatogram Patterns to Mathematically Resolve False Petroleum Hydrocarbon Detections in Clean Organic Soils: A Crude Oil-Spiked Peat Microcosm Experiment. Pages 2197 to 2206 in Environmental Toxicology and Chemistry, Vol. 13, No. 10. McKenzie R.C., Mathers H.M., and Woods S.A Salinity and Cold Tolerance of Ornamental Trees and Shrubs. Soil and Water Agronomy, 1993 Research Report. Alberta Special Crops and Horticultural Research Centre. ASCHRC Pamphlet McKenzie, R.C. and H.G. Najda Salinity Tolerance of Turf and Forage Grasses. Soil and Water Agronomy, 1993 Research Report. Alberta Special Crops and Horticultural Research Centre. ASCHRC Pamphlet Mrowiec, B. et al., Formation and Biodegradation of Toluene in the Anaerobic Sludge Digestion Process. Water Environment Research, 77(3), White, M.L. et al Are biogenic emissions a significant source of summertime atmospheric toluene in the rural northeastern United States? Atmos. Chem. Phys. 9, p Matrix Solutions Inc. 42