J. Brian Leen

Los Gatos Research67 East Evelyn Avenue, Suite 3

Mountain View, CA 94041

b.leen@lgrinc.com650-965-7772

1

About Los Gatos Research

Motivation

Incoherent Cavity Ring-Down Spectroscopy(iCRDS)

Measurement of TCE and PCE

MEW and NAS Moffett Field Superfund Site

Conclusion

Outline

2

About LGR

3

H2O

N2OCO

CO2

NO

NH3O3

VOCs

OCS

CH4HF

HClC2H2

H2O

HONO

C2H4

H2S

NH3

CO2

NO2

Aerosols

• Use optical spectroscopy to make trace gas measurements (ppm, ppb, ppt)

• Operate from the visible to the mid-infrared

• Precise and accurate; also portable, robust and low power

Isotopes

Research Deployments

Deep Sea

UAV

Manned Airborne

Portable Field Station

Why Detect VOCs?

5

BacterialDetection/TypingIndustrial Pollution

Benzene Formaldehyde Acetaldehyde SarinTetrachloroethylene

Chemical WeaponsDetection

USEPA Superfund sitesActive (red), Proposed (yellow), Deleted (green)

MIR Spectra: Molecular “Fingerprint”

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C-HO-H

stretch

C=Cstretch

CH2

bend

Single Laser Scanning Range

External Cavity-QCL (EC-QCL):• Broadly tunable (~2.5 µm)• ~1 cm-1 spectral width• Good for large molecules

Out-of-planebending

C-Ostretch

Incoherent Cavity Ring DownSpectroscopy (iCRDS)

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• High reflectivity mirrors → multiple reflections

• Multiple reflections → very long path

• Long path → high sensitivity

• Light ‘leaks’ out of cavity at measurable rate

• Changes in ‘leak’ rate quantify gas absorption

TCE and PCE Absorption Spectra

8

• PCE and TCE are measurable at ppb concentrations

• Use linear fit to PNNL Spectroscopic Database

• Amplitude ↔ Concentration

• Spectra add linearly

(a) 97.5 ppb PCE (b) 88.7 ppb TCE

Freon-134a

Measurement Linearity

9

• Measurement is linear (R2 = 0.9971)

• Accurate to a few ppb

(a) PCE (b) TCE

Summary of Performance

10

• Field portable

• 50-100’ Teflon sniffing tube

• Robust to H2O, CO2 and other common interferences

• Measurement period: 20 min average

• Precision (1σ):

• PCE – 2.32 ppb (15.9 µg/m3)

• TCE – 1.96 ppb (10.6 µg/m3)

• Limit of Detection:

• PCE < 8 ppb (55 µg/m3)

• TCE < 4 ppb (22 µg/m3)

MEW and Moffett Field

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• Middlefield-Ellis-Whisman(MEW)

• Moffett Field

• Primary contamination:PCE and TCE

o Dry cleaning

o Engine degreasing

o Semiconductormanufacture

Building 10

Previous Measurements

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Sample Location Sample Type

TCE

(µg/m3)

PCE

(µg/m3)

cis-1,2-DCE

(µg/m3)

1,1-DCA

(µg/m3)

1,1-DCE

(µg/m3)

manhole Pathway – Grab 400 300 80J 9 6J

manhole-concrete Pathway – Grab 1,000 900 200 20 10

In B10 near electrical panel Pathway 700 200 100 10 9

In B10 near offices Pathway 1,100 800 200 20 20

In B10 beneath floor Pathway 30 20 6J ND ND

on table in center of B10 Indoor - 24 hr 50 30 8 ND ND

Previous TO-15 measured values (Feb, 2012)

BZ

Mediation Depressurization

Steam TunnelRoute

Steam Gen

Field Setup

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Measurement Protocol:

• Continuous monitoring: Aug. 6-13

• Automatic switching between:

o Tunnel air

o Breathing zone air

o Zero air

o PCE standard

• Remediation fans off Aug 10-13(weekend!)

Building 10 Sample Locations

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Sample Locations:

• Breathing Zone

• 3 Tunnel Locations:

I: Aug 6 – 8

II: Aug 8 – 10

III: Aug 10 –13

BZ

Mediation Depressurization

Steam TunnelRoute

Steam Gen

PCE Standard Repeatability

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• Calculated from first principles

→ No calibration!

• Measured value closely matchesactual value (97.5 ppb)

• Dropouts from liquid nitrogenrefilling

• 1σ precision = 2.9 ppb (19.81 µg/m3)

Breathing Zone:Measured Spectra

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• Recorded sample spectrum every 20 min avg. (each line is a measurement)

• Narrow vertical lines are H2O

• iCRDS accommodates unexpected species

• E.g., characteristic absorption from Freon-152a

Steam Tunnel:Measured Spectra

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• PCE, TCE and cis-1,2-DCE increase visibly when remediation is turned off (8/10)

• TCE & PCE decrease when remediation turned on

• Buildup time constant is about 14 hrs

• Can immediately evaluate remediation efficacy!

ON

OFF

Quantitative PCE and TCE

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• Levels are low with remediation on

• Tunnel air shows consistently higher concentrations

• Huge increase in tunnel concentration with remediation off

• Results match TO-15 measured values (esp. for TCE)

(b) TCE(a) PCE

Practical Implications

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• High resolution site mapping

• Data immediately available

• On site decision making – rapid in, rapid out

• Mobile monitoring

• Minimizes sample handling artifacts

• Potential for measuring reactive species(e.g., acrolein)

• Reduced cost of sampling

Next Steps

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Improved sensitivity

• Optical configuration

• Data processing

• Thermal stability

• Preconcentration

Non-cryogenic detector

• Stirling cooled

• Thermo-electrically cooled

Reduced instrument size

• Improved cavity mirrors

ே

ୀଵ

Spectral acquisition

• Rapid laser scanning

• Improved laser stability

Conclusions

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MIR spectra uniquely identify pollutants inambient air

iCRDS provides sensitivity at the low ppb level

Successfully measured TCE & PCE at MoffettField

Continuous and autonomous for 1 week

iCRDS results agree with TO-15

Observed site remediation dynamics

Doug BaerManish GuptaRobert ProvencalFeng DongElena BermanTom OwanoJim Liem

Acknowledgments

Funding Agencies: DOE, DOD, EPA, NASA, CARB, NIH

Joe HsuCristina Vasquez-Guillamet

Russell DickersonJeffrey W. StehrPatricia CastellanosWinston T. Luke PaulKelleySheryl H. EhrmanLacey Brent

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Marc FisherKen Reichl

Xiao-Ying YuCeline KluzekJohn Hubbe

Alana LeeJoe LukasDaniel MendollaGreg Nagle

Heather Henry

Supplemental Material

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CompoundLOD (3s)

[ppb]Measured Office Levels†

[ppb]

Acetone 0.60 21.8

Benzene 3 0.3 – 18.9

Formaldehyde 4 25.8 – 52.5

Methanol 0.3 ND

Toluene 7 2.6 – 76.9

Acrolein 0.5 ND

Styrene 0.75 0.4 – 18.4

Trimethyl Benzene 5 0.4 – 8.51

m-Xylene 3 3.2 – 75

o-Xylene 3.6 0.7 – 15.5

Trichloroethylene 0.14 0.02 – 23.7

Tetrachloroethylene 0.11 0.1 – 67.8

Simulated Sensitivity Analysis:VOCs in Office Air

†L. C. Holcomb, et al., "Review : Indoor Concentrations of Volatile Organic Compounds: Implications for Comfort, Health andRegulation," Indoor and Built Environment 4, 7-26 (1995). 24

Lab Precision

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TCE Repeated MeasurementsPCE Repeated Measurements

Minimum DetectableConcentration

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PCE MDC TCE MDC

Previous Measurements (ppb)

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Sample Location Sample Type

TCE

(ppb)

PCE

(ppb)

cis-1,2-DCE

(ppb) 1,1-DCA (ppb) 1,1-DCE (ppb)

manhole Pathway - Grab 74 44 20 2.2 1.5

manhole-concrete Pathway - Grab 185 132 50 5 2.5

In B10 near electrical panel Pathway 129 29 25 2.5 2.2

In B10 near offices Pathway 203 117 50 5 5

In B10 beneath floor Pathway 6 3 1.5 ND ND

on table in center of B10 Indoor - 24 hr 9 4 2 ND ND

Previous TO-15 measured values (Feb, 2012)

BZ

Remediation suction

Steam TunnelRoute

Steam Gen

Cost Estimates

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Cost Category Portable GC/MS iCRDSPurchase $75,000 – 175,3751, 2 $45,000 – 110,000Daily Operation $200 – 2502,3 $4 – 10*Personnel (per day) $380 – 540† $0‡ – 230Per Sample Cost - -Total 1st Year $214,200 – 364,975 $45,960 – 165,210

* Includes pump rebuild, electricity, periodic calibration gas, and drying agents ($1-2k/year)† Loaded labor for skilled technician (e.g., BS in Chemistry)‡ Assumes a one in 10 day visitation for data transfer. This may be performed remotely by researches.

(1) C. M. Harris, "Product Review: GC To Go," Analytical Chemistry 74, 585 A-589 A (2002).(2) USEPA, “ENVIRONMENTAL TECHNOLOGY VERIFICATION PROGRAM: FIELD-PORTABLE GC/MS” (Washington, D.C., 1998).(3) USEPA, “Innovations in Site Characterization: Technology Evaluation: Real-Time VOC Analysis Using a Field Portable GC/MS”, Aug 2001.