AWMA 2010 methane forensics in urban setting

Source and Fate of
Methane Within an Urban
Setting
Court D. Sandau, PhD, PChem
(csandau@chemistry-matters.com)
Presented at AWMA Conference 2010
© 2015
Chemistry Matters Inc.

• Thank you to the City of Calgary for
support on this project
• Work presented was published in the
following citation:
• O’Sullivan et al. 2010, Forensics Geo-Gas Investigation of
Methane: Characterization of Sources within an Urban
Setting, Environmental Forensics, 11, 108-116.
Acknowledgements
www.chemistry-matters.com
2© 2015

Outline
• Introduction
• Methane Reference Library
– Project Background
– Sites & Sampling Locations
– Forensic Analytical Program
• Case Study
– Project Background
– Site & Sampling Locations
– Forensic Analytical Program
3© 2015

Methane
• Colorless, odorless, flammable gas
which is typically classified by the
process by which it is formed
• Thermogenic (aka petrogenic):
Abiotic thermal cracking of buried
organic material
• Bacterial: Anaerobic microbial
degradation of organic matter
• CO2 +8H++8e- → CH4 + 2H2O
(Carbonate Reduction)
• CH3COOH → CH4 +CO2
(Acetate Fermentation)
www.cartoonstock.com
4© 2015

Fugitive Methane Emissions
Risk = Asphyxiation and Potential for Explosion
5© 2015

Issues of Concern
The City of Calgary has identified fugitive methane
gas in the subsurface soils of several different areas
of the city
– Unknown source
– Concerned residents
– Possible health risks
– Potential legal action
6© 2015

Forensic GEO-Gas Investigation (FGI)
• Collect gas
samples from
various origins
• Characterize each
source and create a
reference library
• Establish the
composition and
source of the
fugitive gases
through
comparisons with
the reference library 3 Landfills
2 Sewage Treatment
Facilities
2 Natural Gas
4 Sedimentary
Organic Matter*
7© 2015

Investigation
• Historical Review
• Field Measurements,
Fixed Gases e.g. CH4
• Gas samples were
collected in 1-litre gas
bag and CarbotrapTM
• Tiered Forensic
Approach adopted to
identify potential
sources
8© 2015

Tiered Forensic Approach
Hydrocarbon
Content
Volatile Organic Carbon
Content
Level1 Fixed Gas
Radio Active Isotope
(14C)
Stable Isotope Analysis of CH4
Level2
9© 2015

Results of Level 1
10© 2015

Results: Fixed Gas
0
10
20
30
40
50
60
70
80
90
100
Volume(%)
H2S
CH4
CO
N2
CO2
O2
Ar
H2
He
* *
11© 2015

Fixed Gas
0
5
10
15
20
25
30
35
40
45
0 10 20 30 40 50 60 70 80 90
Nitrogen (volume %)
CarbonDioxide(volume%)
Landfill and Sewage
Suspected
Sedimentary
Organic Matter
Thermogenic
Similar to
Atmospheric
Distribution =
OM4 and OM3
Ruled out of
Library
12© 2015

Fixed Gases
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35 40 45
Carbon Dioxide (% volume)
Methane(%volume) Thermogenic
Landfill and Sewage
Suspected Organic
Material
CH4 → Biomass
CH3COOH → CH4 + CO2
CO2 + 8H+ + 8e- → CH4 +
2H2O
CO2 + water → CaCO3 (s)
13© 2015

Results: VOC Fingerprinting
0
10
20
30
40
50
60
Landfill: Chlorinated
Compounds
Sewage: Sulfide
Compounds
Natural Gas: Alkanes
and Alkenes
Volatile Organic Compounds
Concentrationmg/m3
Although CH4 and CO2 dominant: trace gases may
also be present
14© 2015

Results: VOC Fingerprinting
1
0
2
Concentration(mg/m3)
OM3: Acetone; potential to be
mixed source
OM1: BTEXs and
Alkybenzenes; potential to be
mixed source
OM2
15© 2015

0
10
20
30
40
50
60
C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15
Alkanes
Concentrationmg/m3
Natural Gas
Results: HC Fingerprint
16© 2015

0
10
20
30
40
50
60
C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15
Alkanes
Concentrationmg/m3
Landfill
17© 2015

0
10
20
30
40
50
60
C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15
Alkanes
Concentrationmg/m3
Sewage
18© 2015

Summary- Level 1
Source CH4/CO2 Carbon Analysis VOC
Natural Gas + CH4 Low C1 /C1 – C5 Odorants
Landfill CO2 = CH4 High C1 /C1 – C5 Chlorinated compounds
Sewage CO2 = CH4 High C1 /C1 – C5 Sulfur Containing
Natural Organics CO2< CH4 High C1 /C1 – C5 Low
19© 2015

Results of Level 2
20© 2015

Radio Carbon Isotope 14C
Naturally occurring
isotope with a half life of
5730 yrs
Measure in percent
Modern Carbon (pMC)
21© 2015

Radio Carbon Dating
Relies on the radioactive nature and
influence of events such as nuclear
testing and fossil fuel burning
22© 2015

Results: 14C
Post 1950’s
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
14C-CH4 pMC
Landfill (this study)
Sewage
Sedimentary Organic Soil
Natural Gas
Glacial Drift Gas
Landfill (Coleman et al 1995)
Swamp and Marsh
23© 2015

Stable Isotope Fingerprinting
• Atoms of same element with differing masses; same # of
protons, different # of neutrons
• Highly variable in nature and generally endemic of every
organic compound
• Ratio of a pair of isotopes e.g. 13C/12C produces a useful
tracer
p
e-
Hydrogen,1H
n
p
e-
Deuterium,2H, D
n
p n
e-
Tritium,3H, T
99% ~1% <1%
24© 2015

Stable Isotope Analysis
Bacterial MF
13C vs 2H on CH4 Fingerprinting
2H-CH4 (‰)
13C-CH4(‰)
Bacterial
Carbonate
Reduction
Bacterial
migration
after Whiticar, M.J., 1999
Organic matter
25© 2015

Summary of Library
Source CH4/CO2
Carbon
Analysis
VOC
14C –
pMC
δ13C and δ2H of CH4
Thermogenic + CH4
Low C1 /C1 –
C5
Odorants 0 pMC
δ13C = -48‰ to -
40‰
δ2H = -250‰ to -
200‰
Landfill
CO2 =
CH4
High C1 /C1 –
C5
chlorinated
compounds
>100
pMC
δ13C = -60‰ to -52‰
δ2H = -400‰ to -
350‰
Sewage
CO2 =
CH4
High C1 /C1 –
C5
sulfur
containing
>100
pMC
δ13C = -52‰ to -
48‰
δ2H = -425‰ to -
375‰
Natural
Organics
CO2< CH
4
High C1 /C1 –
C5
Low
<100
pMC
δ13C = -63‰ to -50‰
δ2H = -345‰ to -
322‰
Level 1 Level 2
26© 2015

FGI Investigation:
Former Nuisance Grounds
27© 2015

Case History
Pre 1940’s 1950’s 1960’s 1970’s 1980’s 1990’s 2000’s
1953:
nuisance ground
operation began
1963:
nuisance ground
operation closed
2001-2005:
Phase I&II indicate
elevated CH4 Levels
Borrow Pit/
Natural
Vegetation
28© 2015

1969
30© 2015

0.01
0.10
1.00
Concentration(mg/m
3
)
Concentrationmg/m3
Alkane, alkene, cycolalkenes,
alkylbenzene, and BTEXs
TWO SOURCES?
or degradation and one source
32© 2015

Bacterial MF
Clarke Diagram for fingerprinting
2H-CH4 (‰)
13C-CH4(‰)
Bacterial
Carbonate
Reduction
Bacterial
after Whiticar, M.J., 1999
33© 2015

Bacterial MF
Clarke Diagram for well MW03-001
2H-CH4 (‰)
13C-CH4(‰)
Bacterial
Carbonate
Reduction
Bacterial
after Whiticar, M.J., 1999Date CH4 (%)
June 2007
December 2007
May 2009
February 2010
44.12
23.36
27.08
13.24
34© 2015

Results: 14CH4
0
20
40
60
80
100
120
140
160
MW04-006-D MW04-011 MW03-001-D MW04-013 MW03-001-J MW04-006-J
14C-CH4(pMC)
Winter Summer
35© 2015

Two bacterial methane sources of different
ages
Post 1950’s
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
14C-CH4 pMC
Landfill (this study)
Sewage
Sedimentary Organic Soil
Natural Gas
Glacial Drift Gas
Landfill (Coleman et al 1995)
Swamp and Marsh
36© 2015

Three out of four wells analyzed showed methane oxidation was
occurring, suggesting that conditions were naturally present to control
the concentration of methane, therefore, no need to go in and dig out
whole area
Good News for Client
37© 2015

Results of Study:
– Two potential sources identified, landfill and
organic material
– Use of stable and radio isotope not only
indicated source but also gave information
pertaining to the risk associated with the fate
and behavior of elevated methane which
helps client to make decision regarding action
needed
– Tiered Forensic approach required to
confidently identify sources
38© 2015

Contact Info:
Court Sandau
Cell: 1.403.669.8566
Email: csandau@chemistry-matters.com
URL: chemistry-matters.com
Twitter: @Chem_Matters
Slideshare: www.slideshare.net/csandau
© 2015

AWMA 2010 methane forensics in urban setting

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