toluene in peatlands and wetlands · matrix solutions inc. 3 peatlands and wetlands • highly...
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Matrix Solutions Inc. 1
Toluene in Peatlands and Wetlands
Mary Mayes and Sheila Luther October 2015
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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
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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.
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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
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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
Literature Search - Sources of Toluene
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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
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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
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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?
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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
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Determination of “True Biogenic” Samples - F3 Fraction
Adapted from Harris and Bright 2006
Obvious unresolved complex mixture (UCM) present
Largest n-alkane within C13-C18
Elevated sulphur
C10-C19 alkanes with Carbon Preference Index (CPI) ~1
or C19-C32 alkanes with CPI ~1
All false?True Biogenic YesOne or
more are true?
Petrogenic ImpactYes
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Pre
-scr
ee
nin
gT
ier
1 E
va
lua
tio
nT
ier
2 E
va
lua
tio
n
Does the GC-FID pattern in the
peat sample match the GC-FID pattern(s) in the contamination source and/or
backgroundsoil?
No
Yes
No
Yes
Pre-screening requires chromatogram interpretation
expertise
Does the contamination source have an F2:F3b ratio of ≥0.10?
No
Yes
Do the F2 and/or F4 concentrations in the
soil sample exceed soil standards?
Yes
Management required
Management not required
Yes
No
Does the F3 concentration in the soil
sample exceed the soil standard?
Is the F2:F3b ratio in the soil sample
≥0.10?
Does the soil sample biomarker and/or PAH
analysis indicate PHC presence?
Yes
No
No
Do not proceed with evaluation
Exclude sample from evaluation
Management not required
Management required
Management not required
Adapted from Kelly-Hooper et al. 2013
Decision Process for Biogenic F3 Encountered in Organic Soil
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Proposed Decision Process for Biogenic Toluene
Requires specialized testing lab services
VOC markers
Isotopic carbon δC13 analysis
Petrogenic Impact True Biogenic
Process indicates petrogenic?
True
Petrogenic markers present?
Process indicates biogenic?
Biogenic organic compounds
(BOCs) present? Petrogenic markers
absent or trace?
True
Matches contaminated source?
True
Matches biogenic material?
True
If F2 to F4 exceedances use Harris and Bright (2006) and/or
Kelly Hooper et al. (2013) processes
For selected samples and only if required for burden of proof
Conclusions need to be consistent with field observations
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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
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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
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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
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Case Study 1: Assessment, delineation and remediation of hydrocarbon impacts within peatlands at an abandoned well site
NE
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Site Plan
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West – East Cross Section
Organic
Clay Pad
Silty Clay
Weathered Sandstone
Sump Mix Zone
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Soil Quality Results
Toluene, LEPH, HEPH
(Background) Xylenes, VPH, LEPH,
Benzene, Toluene, LEPH, HEPH
Benzene, Toluene
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Soil Quality Results
Contaminants of concern • benzene • toluene • LEPH (C10-C19) • HEPH (C19-C32+)
• Toluene concentration
range 1 to 22.8 mg/kg Extent of impact large if lab results were used as received (no interpretation)
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Soil Quality Results
Contaminants of concern • benzene • toluene • LEPH (C10-C19) • HEPH (C19-C32+)
• Toluene concentration
range 1 to 22.8 mg/kg Extent of impact large if lab results were used as received (no interpretation)
Offsite Toluene
Impacted Area
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Soil Quality Results
Contaminant of concern • benzene
Extent of impact much smaller
Minimizes disturbance to sensitive undisturbed peat land
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VOC scan – Petrogenic Markers
Petrogenic Markers • m, p-xylenes • C3-benzenes • ethyl toluenes • other aromatic hydrocarbons
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VOC Biogenic Markers
Toluene major VOC detected
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VOC Scans – Example Biogenic Markers • camphene • pinene • carene
VOC Biogenic Markers
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Biogenic
Petrogenic
δC13 toluene signature in petrogenic source
range from -22 to -30‰
δC
13
Refined Gasoline or Crude
Peatlands and Wetlands
-30‰
-25‰
-35‰
-40‰
-20‰
Flare Pit
PetrogenicToluene Spikes
SuspectedBiogenic Toluene
Case Study 1 – Carbon Isotopes
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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)
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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?
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Site Surface Water Monitoring
Toluene
Marsh
Deciduous Swamp
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Background Wetland Study
• 15 sites from area sampled
• Sites classified by Alberta Wetland Inventory classification system
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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
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Marsh
Deciduous Swamp
Shallow Open Water
Toluene
Background Wetlands Study - Results
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0.0001
0.001
0.01
0.1
Active Site Deciduous Swamp
Active Site Marsh
Background Deciduous Swamp
Background Marsh
Background Shallow Open Water
Linear (Aquatic Life Guideline)
Sample Series
To
luen
e C
on
cen
trat
ion
(m
g/L)
Toluene Aquatic Life Guideline: 0.0005 mg/L
Toluene Concentrations at Site and Background Surface Water
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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)
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Ab
und
ance
spiking solution contains: nC6, benzene, toluene, ethylbenzene and xylenes
Sample
Blank
Sample S + pike
T Soluene pike
Toluene
Hexanal
O/M/P - Cymene
Eucalyptol
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
VOCs Biogenic Markers VOC Scan – Example Biogenic Markers • Hexanal • O/M/P – Cymene • Eucalyptol
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Biogenic
Petrogenic
δC13 toluene signature in petrogenic source
range from -22 to -30‰
δC
13
Refined Gasoline or Crude
Peatlands and Wetlands
-30‰
-25‰
-35‰
-40‰
-20‰
Flare Pit
PetrogenicToluene Spikes
SuspectedBiogenic Toluene
Case Study 2 Carbon Isotope Result
Case Study 2 Result
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Proposed Decision Process for Biogenic Toluene
Both case studies were able to establish presence of true biogenic toluene
VOC markers
Isotopic carbon δC13 analysis
Petrogenic Impact True Biogenic
Process indicates petrogenic?
True
Petrogenic markers present?
Process indicates biogenic?
Biogenic organic compounds
(BOCs) present? Petrogenic markers
absent or trace?
True
Matches contaminated source?
True
Matches biogenic material?
True
If F2 to F4 exceedances use Harris and Bright (2006) and/or
Kelly Hooper et al. (2013) processes
For selected samples and only if required for burden of proof
Conclusions need to be consistent with field observations
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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
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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
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Thank You Exova
Maxxam
Apache
Further information: Sheila Luther [email protected] 780-989-8335 Mary Mayes [email protected] 403-206-0490
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References Faubert, P. et al. 2010. Non-methane Biogenic Volatile Organic Compound Emissions From A
Subarctic Peatland Under Enhanced UV-B Radiation. Ecosystems 13, p. 860–873.
Fischer-Romero, B. et al., 1996. Tolumonas auensis gen. nov., sp. nov., a toluene-producing bacterium from anoxic sediments of a freshwater lake. Int. J. Syst. Bact., 46(1), 183-188.
Guenther, A. 2013. Biological and Chemical Diversity of Biogenic Volatile Organic Emission In
The Atmosphere. ISRN Atmos. Sciences, Article ID 786290, Hindawi Publishing
Corp. 27 p.
Harris, C. and Bright, D., 2006. 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. 1999. Toluene Emissions from Plants. Geoph. Res. Let., 26(9), p. 1283-
1286.
Jüttner, F. and Henatsch, J.J., 1986. Anoxic hypolimnion is a significant source of biogenic
toluene. Nature, 323, 797-798.
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References
Kelly-Hooper, F., Farewell, A.J., Pike, G., Kennedy, J., Wang, Z., Grunsky, E.C., and Dixon, D.G. 2013. 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. 1994. 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 94-16.
McKenzie, R.C. and H.G. Najda. 1994. Salinity Tolerance of Turf and Forage Grasses. Soil and Water Agronomy, 1993 Research Report. Alberta Special Crops and Horticultural Research Centre. ASCHRC Pamphlet 94-16.
Mrowiec, B. et al., 2005. Formation and Biodegradation of Toluene in the Anaerobic Sludge Digestion Process. Water Environment Research, 77(3), 274-278.
White, M.L. et al. 2009. Are biogenic emissions a significant source of summertime atmospheric toluene in the rural northeastern United States? Atmos. Chem. Phys. 9, p. 81-92.