Gas Monitoring by QMSGas Monitoring by QMS Present Situation and Future Prospects Fumiaki Tsunomori...

Gas Monitoring by QMSPresent Situation and Future Prospects

Fumiaki Tsunomori1), Sanae Koizumi1),Koji Shimada2), Tomohiko Saito3), Hidemi Tanaka3)

Kenji Notsu1)

1) Laboratory for Earthquake Chemistry, Graduate School of Science,University of Tokyo

2) Tono Geoscience Center, JAEA3) Department of Earth & Planetary Science, Graduate School of Science,

University of Tokyo

The 6th Taiwan - Japan Joint Workshop on Hydrological and Geochemical Research for Earthquake Prediction

Colleagues

Dr. ShimadaMs. Koizumi

Mr. Saito Prof. Tanaka Prof. Notsu


Outline

• Mass Spectrometry

• Gas Monitoring for Earthquake Research

• Gas Monitoring for Elemental Process Research

• Next Stage of Gas Monitoring by QMS


Mass Spectrometry

Magnetic Field

m+

2

21 mv

+

z

y

x

x-z planeheavy

light

Electric Field

Principle: Trajectory of a cation is determined by mass weight

m+

S

heavy

light

2

21 mv

z

y

x

y-z plane

N

Gas composition can be analyzed by mass weight of molecules


Quadrupole Mass Spectrometer (QMS)

Quadrupole: Motion of a cation is governed by Mathieu’s equation

0)cos(22

02

2

=−+ xtVUmr

Zedt

xd ω

x

y

)cos( tVURFy ω−−=

tVURFx ωcos−=

0

1

2

3

4

5

0 1 2 3 4 5

-a0b1

-b1

a1

b2

a

q

220

220

4,8ωω mr

ZeVqmr

ZeUa ==

a-q stability diagram of Mathieu’s equation

Quadrupole behaves as a mass filter under stated electronic condition


QMS as Gas Monitor

Advantage: Isotope analysis, High sensitivity, High time resolution

Quadrupole mass spectrometer is useful for a long-term observation

Yang, et al. (2006)Tsunomori, et al. (submitted)

Shimada, et al. (in preparation)

Gas monitoring using a QMS was realized by Takahata et al. in 1997.


Gas Composition Change in Spring Water

Sugisaki, et al. (1996)

coseismic

preseismic

preseismic?

Spring water gathers chemical substances from wide area

Monitored by a gas chromatograph with oxygen carrier.


Gas Composition Change in Mud-Pool Bubble

Chung-lun mud-pool

T.F. Yang, et al. (2006)

Gas concentration in groundwater can be perturbated by many causes

Monitoring subsurface gas must be helpful for earthquake prediction


Spike-like Methane Concentration Change

Groundwater flow affect methane concentration in groundwater, too

Tsunomori, et al. (submitted)

Gas concentration in groundwater can be perturbated by many causes

0

10

20

30

40

C methene[a

.u.]

0

10

20

30

40

0 336 672 1008 1344Mass

Cu

rren

t/1

0-9[A

]

Time [h]

( ))(exp1 0

max

wwrC

C−−+

=

VP


Spring Water of Active Fault

Deep subsurface gas is included in fault gas

Active fault is connected to a focal region

Shimada, et al. (in preparation)

ppm Miya-kawa rv.

SpringWater

Na 3.3 333.1NH4 0.0 0.0K 1.5 4.5Mg 1.0 4.2Ca 15.2 14.9Cl 2.3 199.2NO3 0.3 0.0SO4 3.9 3.5HCO3 53.2 610.8

Air Spring Water #1 Spring Water #23He/4He /10-6 1.4 2.42 2.394He (ppm) 5.6 778 763


3He/4He and Low Frequency Tremor

Low frequency tremor is thought to be related to fluid generation in the crust

Spatio-temporal monitoring of 3He/4He will be a powerful tool for constraining the underground structure

Dogan, et al. (2007)

Deep Tremor, Obara (2002)> 1.2 RA


Gas Monitoring for Earthquake Research

• Monitoring subsurface gas must be helpful for earthquake prediction

• Groundwater flow also affect methane concentration in groundwater

• Deep subsurface gas is included in fault gas

• Spatio-temporal monitoring of 3He/4He will be a powerful tool for constraining the underground structure


Methane Emission under Compressive Force

Cylindrical granite is uni-axially compressed in a vacuum chamber

Inada Granite (Ibaragi, Japan)Size: 0.5-4.0mmQuartz 31%, Feldspar 63%, Biotite 4%

CCG

RP

PG

TMP

QMS

101 Pa10-7 Pa

0

20

40

0 1 2 3Time/103 [s]

Load

/[ton

]


Methane Emission and Compressive Rate

Methane concentration in the chamber is analyzed by a QMS

Temporal change of methane concentration seems to depend on compressive rateTime

0 0.25 0.5 1.00.75

Tota

l Gas

[Pa]

0

200

400

600

800

CH

4co

nc.[

%]

0

0.4

0.8

1.2

22 kPa/s11 kPa/s

22 kPa/s11 kPa/s

Koizumi, et. al (in preparation)


-20

0

20

40

60

80

100

1200 1500 1800 2100 2400 2700 3000Wavenumber [cm-1]

Intensity [a.u.]

Methane Concentration in a Rock

Methane source is thought to be minerals

Methane concentration may reflect the amount of cracks generated in a rock

CCG

RP

PG

TMP

QMS

101 Pa

10-7 Pa

Whole rock

Qz

Fd

Bt

mixture

CH4 conc.[cm3STP/g]

Qz 0.20 ±0.06

Fd 0.08 ±0.05

Bt 0.4 ±0.1

0.9 g

CH4 conc.[cm3STP/g]

Granite 0.17 ±0.06

Mixture 0.14 ±0.05

Calc.* 0.14 ±0.06* Inada Granite: Qz 31%, Fd 63%, Bt 4%


Methane Included in a Rock

Granitic rocks of Atotsugawa active fault were grinded in a closed cell

Methane is not reaction product but included in a rock

Saito, et. al (in preparation)

Gas

/µm

ol

Surface Increase ∆S /m2

( ))exp(1)( SkASC ∆−−=∆

SBSC ∆=∆ )(

Mechano-chemical reaction

Emission phenomenon


Gas Monitoring for Elemental Process Research

• Emission behavior of methane from a granite seems to depend on compressive rate.– The dependency is being confirmed now.

• The methane source is inclusions in minerals

• The amount of methane emitted may indicate degrees of crack generation.


Next Stage of Gas Monitoring by QMS

• Spatio-temporal monitoring of 3He/4He must be important for earthquake prediction research.– Active fault zone– Area above focal region of low frequency tremor– Hot spring

• High performance mass spectrometer is definitely required.


Development of High Resolution QMS

QMS should be driven in the second stability region

Mass weight of 3He is very close to that of HD

M∆

M 'M

Molecule Weight [u]

3 3He+

T+

HD+

H3+

3.0160303.0160503.0218253.023475

4 4He+

HT+

D2+

H2D+

4.0026004.0238754.0282044.029650

( ) 500-0.16784

126.0≥=

∆ VUMM

336.0≥qa

168.02

≥=qa

VU

0

1

2

3

4

5

0 1 2 3 4 5

-a0b1 -b1

a1

b2

q

a


Requirement for High Resolution QMSa

a

2.5

2.7

2.9

3.1

2.7 2.8 2.9 3 3.1 3.2 3.3

-a0

-b1

a1

b2

q

Second Stability Region

Quadrupole must be driven in the second stability region

220

4ωmr

eVq =

53.2,81.2 == aq

（2.81530433,2.521000064） -1910491.60217733 ×=e-27101.66053873×=u

5~1:m

29.23~66.4:U220

8ωmr

eUa =

74.51~35.10:V

f = 5 [MHz]

r0 = 1.5 [mm]

0r

Problem is only to make an electric circuit for RF voltage generation


Summary

• Gas monitoring is powerful tool for groundwater (geochemical) research related to earthquakes

• Laboratory experiments are important for understanding mechanism of observation results

• Spatio-temporal monitoring of 3He/4He must be important for earthquake prediction research.

Gas Monitoring by QMSGas Monitoring by QMS Present Situation and Future Prospects Fumiaki Tsunomori...

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