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NO 2 Measurements with Different Converters

NO 2 Measurements with Different Converters. Molybdenum Converters vs. Specific NO 2 Converters Robert Gehrig; Christoph Hüglin, Beat Schwarzenbach EMPA Dübendorf Switzerland Air Pollution / Environmental Technology. Outline. EMEP vs. EU Directive NO 2 automatic measurement techniques

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NO 2 Measurements with Different Converters

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  1. NO2 Measurements with Different Converters Molybdenum Converters vs. Specific NO2 Converters Robert Gehrig; Christoph Hüglin, Beat Schwarzenbach EMPA Dübendorf Switzerland Air Pollution / Environmental Technology

  2. Outline • EMEP vs. EU Directive • NO2 automatic measurement techniques • Results of parallel measurements • Conclusions R. Gehrig; EMEP TFMM 2011

  3. NO2 : EMEP vs. EU Directive • EMEP: • Specific NO2measurementsrequired. • NaImanualmethodasstandardtechnique. • Automaticspecificmonitoringwithphotolyticconverters. • EU Directive (compliancemeasurements): • Measurement withchemiluminescence after conversionof NO2to NO asstandardtechniqueaccordingto EN 14’211. • Not specific. R. Gehrig; EMEP TFMM 2011

  4. NO2 : Molybdenum converter • Standard technique: Measurement of NO withchemiluminescence • NO2isreducedto NO by a converterHeatedmetalconverters, mostlymolybdenum (Mo) • Efficient, longlifetime, reliable • not specificNOx = NO + a·NO2 + b·HNO3+ c·NO3-+ d·PAN + e·NH3 + … R. Gehrig; EMEP TFMM 2011

  5. NO2 : Photolytic converter • Principle: NO2 is reduced photolytically to NO NO2 + hν NO + O hν: < 410nm O + O2 O3 NO + O3 NO2 + O2 NO2 + O2 + hν NO + O3 • Light source: Xe-vapour lamp, metal halid lampe of Array of UV-LED • Specific, but low converter efficiency • Converter efficiency needs to be calibrated at regular intervals R. Gehrig; EMEP TFMM 2011

  6. „Blue Light Converter“ BLC Cell volume: 17ml Cell purge time at 1 l/min: 1s Array von UV-LED‘s  ca. 380 - 410nm Air Quality Design, Inc., Wheatridge, CO, (USA)(formerly: Droplet Measurement Technologies, Inc., Boulder) Sale in Europa: meteorologie consult gmbh, D-Königstein (www.metcon.de) R. Gehrig; EMEP TFMM 2011

  7. Set-up of NOx-monitor with BLC Molybdenum converter replaced or bypassed, flow-controll capillary after converter Example: Thermo Electron Model 42C TL Mo-Konverter NO2-Konverter NOx BLC Sample Filter NO R.C. PMT Trockner Vor-kammer Ozonator Pumpe R. Gehrig; EMEP TFMM 2011

  8. BLC integrated in NOx monitor Thermo Electron Model 42i TL Thermo Electron Model 42C TL R. Gehrig; EMEP TFMM 2011

  9. Specific NO2 measurements in NABEL(NABEL = Swiss National Monitoring Network) 1) Cranox: Chemiluminescence monitor (CLD770AL ppt resp. CLD 89p) with photolytic converter (PLC 760 with Xe-vapour lamp or PLC 762 mit metal halid lamp), Eco Physics. Sites with NO2 measurements with photolytic converters: R. Gehrig; EMEP TFMM 2011

  10. Comparison Cranox – BLC Daily means at Rigi-Seebodenalp • NO Daily means at Rigi-Seebodenalp NO2 R. Gehrig; EMEP TFMM 2011

  11. NO2 (photolytic) at different sites R. Gehrig; EMEP TFMM 2011

  12. NO2 comparison Payerne Rigi R. Gehrig; EMEP TFMM 2011

  13. NO2 at different sites daily means R. Gehrig; EMEP TFMM 2011

  14. Mean values (Jan – Oct 2010) Jungfraujoch 0.23 ppb 0.84 ppb 1) 0.61 ppb 1) 73 % 1) Jungfaujoch: NO2 (Mo) is NOy – NO; NO2 is NOy-NO-NO2; means 2005-2009 R. Gehrig; EMEP TFMM 2011

  15. New spectroscopic laser techniques • Cavity-Enhanced-Absorption-Spectroscopy • Cavity-Ring-Down-Spectroscopy • Quantum Cascade Laser Spectroscopy R. Gehrig; EMEP TFMM 2011

  16. Conclusions • NO2 measurements with molybdenum converters overestimate NO2 by 10-70%. • Photolytic converters and new spectroscopic methods allow for automatic specific NO2 measurements. • Choice of method depends on the aim of the measurements. • Clear specification of methods is needed for NO2 data series. R. Gehrig; EMEP TFMM 2011

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