J. Brian LeenLos Gatos Research67 East Evelyn Avenue, Suite 3   Mountain View, CA 94041     b.leen@lgrinc.com        650-9...
Outline About Los Gatos Research Motivation Incoherent Cavity Ring-Down Spectroscopy  (iCRDS) Measurement of TCE and P...
About LGR            VOCs                                                Aerosols         O3    NH3            OCS        ...
Research Deployments                                                UAVManned Airborne            Deep Sea                ...
Why Detect VOCs?                                                               Bacterial          Chemical Weapons        ...
MIR Spectra: Molecular “Fingerprint”                              Single Laser Scanning Range                          C=C...
Incoherent Cavity Ring Down                 Spectroscopy (iCRDS)• High reflectivity mirrors → multiple reflections• Multip...
TCE and PCE Absorption Spectra(a) 97.5 ppb PCE                      (b) 88.7 ppb TCE      Freon-134a• PCE and TCE are meas...
Measurement Linearity(a) PCE                                   (b) TCE  • Measurement is linear (R2 = 0.9971)  • Accurate ...
Summary of Performance• Field portable• 50-100’ Teflon sniffing tube• Robust to H2O, CO2 and other common interferences• M...
MEW and Moffett Field• Middlefield-Ellis-Whisman  (MEW)• Moffett Field• Primary contamination:  PCE and TCE    o Dry clean...
Previous Measurements                        Previous TO-15 measured values (Feb, 2012)                                   ...
Field SetupMeasurement Protocol:• Continuous monitoring: Aug. 6-13• Automatic switching between:    o Tunnel air    o Brea...
Building 10 Sample LocationsSample Locations:• Breathing Zone• 3 Tunnel Locations:     I: Aug 6 – 8       II: Aug 8 – 10...
PCE Standard Repeatability• Calculated from first principles    → No calibration!• Measured value closely matches  actual ...
Breathing Zone:                     Measured Spectra• Recorded sample spectrum every 20 min avg. (each line is a measureme...
Steam Tunnel:                        Measured Spectra• PCE, TCE and cis-1,2-DCE increase visibly when remediation is turne...
Quantitative PCE and TCE      (a) PCE                                     (b) TCE• Levels are low with remediation on• Tun...
Practical Implications• High resolution site mapping• Data immediately available• On site decision making – rapid in, rapi...
Next Steps                 ே                       ௞                ௞ୀଵImproved sensitivity                               ...
Conclusions MIR spectra uniquely identify pollutants in  ambient air iCRDS provides sensitivity at the low ppb level Su...
Acknowledgments                                   Alana Lee                                   Joe LukasDoug Baer          ...
Supplemental Material                        23
Simulated Sensitivity Analysis:                                                      VOCs in Office Air                   ...
Lab PrecisionPCE Repeated Measurements    TCE Repeated Measurements                                                       ...
Minimum Detectable        ConcentrationPCE MDC            TCE MDC                             26
Previous Measurements (ppb)                        Previous TO-15 measured values (Feb, 2012)                             ...
Cost Estimates                     Cost Category                     Portable GC/MS                        iCRDS          ...
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Laser based Spectrometer for VOCs Monitoring

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Presentation to the Moffett Restoration Advisory Board on November 29, 2012.

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Laser based Spectrometer for VOCs Monitoring

  1. 1. J. Brian LeenLos Gatos Research67 East Evelyn Avenue, Suite 3 Mountain View, CA 94041 b.leen@lgrinc.com 650-965-7772 1
  2. 2. Outline About Los Gatos Research Motivation Incoherent Cavity Ring-Down Spectroscopy (iCRDS) Measurement of TCE and PCE MEW and NAS Moffett Field Superfund Site Conclusion 2
  3. 3. About LGR VOCs Aerosols O3 NH3 OCS NO2 CO2 H2O H2O HF CO2 CH4 CO N2O NO HCl C2H4 C2H2 NH3 HONO H2S Isotopes• 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 3
  4. 4. Research Deployments UAVManned Airborne Deep Sea Portable Field Station
  5. 5. Why Detect VOCs? Bacterial Chemical Weapons Industrial Pollution Detection/Typing DetectionUSEPA Superfund sitesActive (red), Proposed (yellow), Deleted (green) Benzene Formaldehyde Tetrachloroethylene Acetaldehyde Sarin 5
  6. 6. MIR Spectra: Molecular “Fingerprint” Single Laser Scanning Range C=C C-O Out-of-plane C-H stretch stretch bending O-H stretch CH2 bend External Cavity-QCL (EC-QCL): • Broadly tunable (~2.5 µm) • ~1 cm-1 spectral width • Good for large molecules 6
  7. 7. Incoherent Cavity Ring Down Spectroscopy (iCRDS)• 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 7
  8. 8. TCE and PCE Absorption Spectra(a) 97.5 ppb PCE (b) 88.7 ppb TCE Freon-134a• PCE and TCE are measurable at ppb concentrations• Use linear fit to PNNL Spectroscopic Database• Amplitude ↔ Concentration• Spectra add linearly 8
  9. 9. Measurement Linearity(a) PCE (b) TCE • Measurement is linear (R2 = 0.9971) • Accurate to a few ppb 9
  10. 10. Summary of Performance• 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) 10
  11. 11. MEW and Moffett Field• Middlefield-Ellis-Whisman (MEW)• Moffett Field• Primary contamination: PCE and TCE o Dry cleaning o Engine degreasing o Semiconductor manufacture Building 10 11
  12. 12. Previous Measurements Previous TO-15 measured values (Feb, 2012) TCE PCE cis-1,2-DCE 1,1-DCA 1,1-DCESample Location Sample Type (µg/m3) (µg/m3) (µg/m3) (µg/m3) (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 Mediation Depressurization BZ Steam Tunnel Route Steam Gen 12
  13. 13. Field SetupMeasurement 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!) 13
  14. 14. Building 10 Sample LocationsSample Locations:• Breathing Zone• 3 Tunnel Locations:  I: Aug 6 – 8  II: Aug 8 – 10  III: Aug 10 –13Mediation Depressurization BZ Steam Tunnel Route Steam Gen 14
  15. 15. PCE Standard Repeatability• Calculated from first principles → No calibration!• Measured value closely matches actual value (97.5 ppb)• Dropouts from liquid nitrogen refilling• 1σ precision = 2.9 ppb (19.81 µg/m3) 15
  16. 16. Breathing Zone: Measured Spectra• 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 16
  17. 17. Steam Tunnel: Measured Spectra• 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 17
  18. 18. Quantitative PCE and TCE (a) PCE (b) TCE• 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) 18
  19. 19. Practical Implications• 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 19
  20. 20. Next Steps ே ௞ ௞ୀଵImproved sensitivity Non-cryogenic detector • Optical configuration • Stirling cooled • Data processing • Thermo-electrically cooled • Thermal stability • Preconcentration Spectral acquisitionReduced instrument size • Rapid laser scanning• Improved cavity mirrors • Improved laser stability 20
  21. 21. Conclusions MIR spectra uniquely identify pollutants in ambient air iCRDS provides sensitivity at the low ppb level Successfully measured TCE & PCE at Moffett Field  Continuous and autonomous for 1 week  iCRDS results agree with TO-15  Observed site remediation dynamics 21
  22. 22. Acknowledgments Alana Lee Joe LukasDoug Baer Daniel Mendolla Heather HenryManish Gupta Greg NagleRobert ProvencalFeng DongElena Berman Russell DickersonTom Owano Jeffrey W. StehrJim Liem Patricia Castellanos Winston T. Luke Paul Marc Fisher Kelley Ken Reichl Sheryl H. Ehrman Lacey Brent Joe Hsu Cristina Vasquez-Guillamet Xiao-Ying Yu Celine Kluzek John Hubbe Funding Agencies: DOE, DOD, EPA, NASA, CARB, NIH 22
  23. 23. Supplemental Material 23
  24. 24. Simulated Sensitivity Analysis: VOCs in Office Air LOD (3s) Measured Office Levels† Compound [ppb] [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†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
  25. 25. Lab PrecisionPCE Repeated Measurements TCE Repeated Measurements 25
  26. 26. Minimum Detectable ConcentrationPCE MDC TCE MDC 26
  27. 27. Previous Measurements (ppb) Previous TO-15 measured values (Feb, 2012) TCE PCE cis-1,2-DCESample Location Sample Type (ppb) (ppb) (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 Remediation suction BZ Steam Tunnel Route Steam Gen 27
  28. 28. Cost Estimates Cost Category Portable GC/MS iCRDS Purchase $75,000 – 175,3751, 2 $45,000 – 110,000 Daily Operation $200 – 2502,3 $4 – 10* Personnel (per day) $380 – 540† $0‡ – 230 Per 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. 28
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