The miniDOAS    a low-cost ammonia sensor    using UV spectrometry1   09 October 2012
Contents    1.   Why measure ammonia?    2.   Why use an optical method?    3.   What is DOAS?    4.   How we built a low-...
About RIVMRijksinstituut voor Volksgezondheid en MilieuDutch National Institute for Public Health and the Environment:a le...
Ammonia in the environment: a problem!● Eutrophication and loss of biodiversity● Soil acidification● Source of particulate...
Ammonia sourcesIn the Netherlands: 90% from agriculture5                                The miniDOAS | 09 October 2012
The ammonia life cycleemission         emission                deposition              deposition                         ...
Measuring ammonia in the atmosphere (1)                       Atmospheric ammonia                       concentrations:   ...
Measuring ammonia in the atmosphere (2)                       Ammonia deposition and                       emission:      ...
Ammonia concentrations – difficult to measure● Traditional sensors suck in air to measure.● Ammonia is “sticky”; ammonia s...
DOAS: an optical measurement techniqueDOAS: Differential Optical Absorption SpectroscopyMeasures concentrations using spec...
DOAS measurement technique  telescope and xenon lamp           open path                        reflector085123428110     ...
DOAS measurement techniquetelescope and xenon lamp                                            reflector                Xe-...
DOAS measurement techniquetelescope and xenon lamp                                            reflector                Xe-...
DOAS measurement techniquetelescope and xenon lamp                                            reflector                Xe-...
DOAS measurement techniquetelescope and xenon lamp                                            reflector                Xe-...
DOAS measurement techniquetelescope and xenon lamp                                                             reflector  ...
DOAS measurement techniquetelescope and xenon lamp                                                    reflector           ...
Trace gases in the UV                                                           -17NO and SO2 have                        ...
20                    Data analysis–curve fitting                                                                         ...
RIVM DOAS to measure ammonia concentrations20                   The miniDOAS | 09 October 2012
RIVM DOAS to measure ammonia concentrations                              xenon arc lamp                                   ...
RIVM DOASgreat instrument, greatperformance:+ high up-time+ low maintenance+ high resolution ( 0.15 µg/m3)+ no interferenc...
We need a low-cost DOAS…● To replace the ageing monitors in the  monitoring network● To conduct ammonia deposition  studie...
miniDOAS: setup        parabolic reflector   xenon arc lamp                                                        open   ...
miniDOAS: setup25                The miniDOAS | 09 October 2012
miniDOAS26         The miniDOAS | 09 October 2012
miniDOAS performance      Ammonia concentration (µg m )     -3                                      60         RIVM DOAS  ...
miniDOAS performance     NH3 concentration (µg m ) -3                                 60                                  ...
miniDOAS performance                    200 miniDOAS (µg m )                    150-3                                     ...
miniDOAS and RIVM DOAS        RIVM DOAS                                 miniDOAS ● resolution: 0.15 µg/m3         ● resolu...
The miniDOAS – what makes it work?                      150 W xenon arc lamp Fiber: transmittance ~ 5%                    ...
The miniDOAS – what makes it work?                                                A large portion of the lamp             ...
Conclusions and outlookRIVM DOAS+ high-performance spectrograph- inefficient light sender- loss of light in optical fibrem...
Conclusions and outlook● Further develop the miniDOAS into a commercially available  instrument● Replace the ageing Nation...
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Stijn Berkhout - RIVM

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Stijn Berkhout - RIVM

  1. 1. The miniDOAS a low-cost ammonia sensor using UV spectrometry1 09 October 2012
  2. 2. Contents 1. Why measure ammonia? 2. Why use an optical method? 3. What is DOAS? 4. How we built a low-cost optical ammonia sensor.2 The miniDOAS | 09 October 2012
  3. 3. About RIVMRijksinstituut voor Volksgezondheid en MilieuDutch National Institute for Public Health and the Environment:a leading centre of expertise in the fields of health, nutrition and environmental protection3 The miniDOAS | 09 October 2012
  4. 4. Ammonia in the environment: a problem!● Eutrophication and loss of biodiversity● Soil acidification● Source of particulate matter4 The miniDOAS | 09 October 2012
  5. 5. Ammonia sourcesIn the Netherlands: 90% from agriculture5 The miniDOAS | 09 October 2012
  6. 6. The ammonia life cycleemission emission deposition deposition or emissionfrom livestock from manured on or from on naturehousing fields agricultural land areas 6 The miniDOAS | 09 October 2012
  7. 7. Measuring ammonia in the atmosphere (1) Atmospheric ammonia concentrations: measured in the Dutch National Air Quality Monitoring Network7 The miniDOAS | 09 October 2012
  8. 8. Measuring ammonia in the atmosphere (2) Ammonia deposition and emission: measured in research projects8 The miniDOAS | 09 October 2012
  9. 9. Ammonia concentrations – difficult to measure● Traditional sensors suck in air to measure.● Ammonia is “sticky”; ammonia sticks to tubes and inlets, causing delay effects.● Ammonium aerosols also get stuck to filters and tubes and cause interference when they dissociate.How to solve these problems? wet chemical ammonia sensor9 The miniDOAS | 09 October 2012
  10. 10. DOAS: an optical measurement techniqueDOAS: Differential Optical Absorption SpectroscopyMeasures concentrations using specific absorption features and the Lambert-Beer law 20 optical absorption spectrum of ammonia Cross section 15 cm ) 2 10 -18 (x10 5 0 200 205 210 215 220 225 Wavelength (nm)10 The miniDOAS | 09 October 2012
  11. 11. DOAS measurement technique telescope and xenon lamp open path reflector085123428110 Xe-lamp spectrum 11 The miniDOAS | 09 October 2012
  12. 12. DOAS measurement techniquetelescope and xenon lamp reflector Xe-lamp spectrum Xe + NH3 spectrum12 The miniDOAS | 09 October 2012
  13. 13. DOAS measurement techniquetelescope and xenon lamp reflector Xe-lamp spectrum Xe + NH3 spectrum13 The miniDOAS | 09 October 2012
  14. 14. DOAS measurement techniquetelescope and xenon lamp reflector Xe-lamp spectrum Xe + NH3 spectrum14 The miniDOAS | 09 October 2012
  15. 15. DOAS measurement techniquetelescope and xenon lamp reflector Xe-lamp spectrum Xe + NH3 spectrum15 The miniDOAS | 09 October 2012
  16. 16. DOAS measurement techniquetelescope and xenon lamp reflector 100000 xenon lamp spectrum intensity (a.u.) xenon lamp + NH3 spectrum 10000 1000 200 205 210 215 220 225 230 wavelength (nm)16 The miniDOAS | 09 October 2012
  17. 17. DOAS measurement techniquetelescope and xenon lamp reflector Differential spectrum: (xenon lamp + NH3) / xenon lamp 1.1 1.0 0.9 0.8 0.7 200 205 210 215 220 225 230 wavelength (nm)17 The miniDOAS | 09 October 2012
  18. 18. Trace gases in the UV -17NO and SO2 have 10strong lines in the Molecular cross section (cm ) 2range 200-230 nm. 10 -19 SO2 NH3This means we can -21 NO 10measure NO and 10 -17 O3SO2 as well. -19 NO2 10 N2O -21Other gases have 10 O2no absorption -23 CO2 10features in this -25range. 10 200 210 220 230 Wavelength (nm)18 The miniDOAS | 09 October 2012
  19. 19. 20 Data analysis–curve fitting NH3 spectrum 0 -20 Measured DOAS curve Fit spectrum NH3 1.0 -40DOAS curve (a.u.) 200 205 210 215 220 225 230 20 0.5 NO spectrum (a.u.) 0.0 0 -0.5 -20 Fit spectrum NO -1.0 200 205 210 215 220 225 230 -40 200 205 210 215 220 225 230 20 SO2 spectrum (a.u.) Least square fit: 0 iQ   (DOASi    NH3i    NOi -   SO2i ) 2 2 -20 i0 Fit spectrum SO2 -40 200 205 210 215 220 225 230 19 The miniDOAS | 09 October 2012
  20. 20. RIVM DOAS to measure ammonia concentrations20 The miniDOAS | 09 October 2012
  21. 21. RIVM DOAS to measure ammonia concentrations xenon arc lamp zinc lamp (for calibration) telescope motion controller CCD controller stepper motors Peltier-cooled CCD detector optical fibre lamp power supply computer spectrograph21 The miniDOAS | 09 October 2012
  22. 22. RIVM DOASgreat instrument, greatperformance:+ high up-time+ low maintenance+ high resolution ( 0.15 µg/m3)+ no interference or delay effects- complicated instrument- high price tag (~ € 200 000)22 The miniDOAS | 09 October 2012
  23. 23. We need a low-cost DOAS…● To replace the ageing monitors in the monitoring network● To conduct ammonia deposition studies23 The miniDOAS | 09 October 2012
  24. 24. miniDOAS: setup parabolic reflector xenon arc lamp open telescope path mirror folding mirror retro- reflector gas cell (optional) spectrograph24 The miniDOAS | 09 October 2012
  25. 25. miniDOAS: setup25 The miniDOAS | 09 October 2012
  26. 26. miniDOAS26 The miniDOAS | 09 October 2012
  27. 27. miniDOAS performance Ammonia concentration (µg m ) -3 60 RIVM DOAS miniDOAS 40 20 0 21 22 23 24 25 26 27 Date in December 200927 The miniDOAS | 09 October 2012
  28. 28. miniDOAS performance NH3 concentration (µg m ) -3 60 RIVM DOAS miniDOAS 40 20 0 12:00 18:00 00:00 06:00 12:00 24-12-2009 25-12-2009 Date and time28 The miniDOAS | 09 October 2012
  29. 29. miniDOAS performance 200 miniDOAS (µg m ) 150-3 scatterplot of ammonia concentrations linear fit 100 2 y = 0.987(1) x + 0.402(17), R = 0.996 50 0 0 50 100 150 200 -3 RIVM DOAS (µg m )29 The miniDOAS | 09 October 2012
  30. 30. miniDOAS and RIVM DOAS RIVM DOAS miniDOAS ● resolution: 0.15 µg/m3 ● resolution: 0.07 µg/m3 ● ~ € 200 000 ● ~ € 15 000 How is this possible?30 The miniDOAS | 09 October 2012
  31. 31. The miniDOAS – what makes it work? 150 W xenon arc lamp Fiber: transmittance ~ 5% Only a small portion of the lamp energy is transmitted: ~ 1.5%5 minutesacquisition:120 spectra RIVM DOAS31 The miniDOAS | 09 October 2012
  32. 32. The miniDOAS – what makes it work? A large portion of the lamp energy is transmitted: ~ 60%5 minutes No loss due toacquisition: optical fiber3000 spectra spectrograph miniDOAS32 The miniDOAS | 09 October 2012
  33. 33. Conclusions and outlookRIVM DOAS+ high-performance spectrograph- inefficient light sender- loss of light in optical fibreminiDOAS- low-cost components+ efficient light sender+ direct coupling, no fibre33 The miniDOAS | 09 October 2012
  34. 34. Conclusions and outlook● Further develop the miniDOAS into a commercially available instrument● Replace the ageing National Air Quality Monitoring Network ammonia monitors with miniDOASes● Start ammonia deposition studies with miniDOASes● Spread the instrument around the world34 The miniDOAS | 09 October 2012

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