EAS 4/8803: Experimental Methods in AQ Week 9: Air Quality Management (AQM) Clean Air Act (History, Objectives, NAAQS) Emissions and Atmospheric Trends (Links) Principal Measurement Techniques (O3, NOx, CO, SO2, Pb, PM) Measurement of CO (Exp 5) NDIR Method (Interferences, Stability, DL, Precision, Accuracy) Controlling O3 Why controlling O3 (Agriculture, Health) Photochemical Processes (NOx vs VOC sensitivities, limitations) Ambient Measurements and Trends (World, USA, GA) Measurement of O3 (Exp 6) UV Absorption (Interferences, Stability, DL, Precision, Accuracy) March 15, 2004 EAS 4/8803

Physical and Chemical Measuring Principles March 15, 2004 EAS 4/8803

Applied Measuring Techniques March 15, 2004 EAS 4/8803

Photometry: IR Absorption Bands March 15, 2004 EAS 4/8803

Photometry: UV Absorption Spectra March 15, 2004 EAS 4/8803

NO/NOy Analyzer Inlet Box MoO / Au ~350oC March 15, 2004 EAS 4/8803

NO/NOx/NOy Method: Chemiluminescence From inlet box Excess O3 C NC NO Chemi-lumi-nescence 600-3200 max 1200 nm Reaction Vessel Zero Volume O3 Trap PMT HV Hz NO + O3 NO2* + O2 NO + O3 NO2 + O2 NO2* NO2 + hv NO2* + M NO2 + M Chemiluminescence of NO and all reduced NOy species: Converter efficiency critical!! NO2, NO3, N2O5, HONO, HNO3, aerosol NO3-, PAN and other organic nitrates March 15, 2004 EAS 4/8803

NO/NOy Analyzer Operation SnoopNOy_cps: Photon counts per s NOyNO: NO measure mode NOy: NOy measure mode NOyNO0: NO zero mode NOy0: NOy zero mode Sensitivities (cps/ppt) S_NO = (NOcal-NOipol)/[NOnom] S_NO2 =(NOyNO2cal-NOyipol)/[NO2nom] S_NPN=(NOyNPNcal-NOyipol)/[NPNnom] S_HNO3=(NOyHNO3cal-NOyipol)/[HNO3nom] MR Calculation NO (ppbv) = (NO-ZVeff*NO0)/S_NO NOy (ppbv) = (NOy-ZVeff*(NOy0-NO0)-NO)/S_NO2 + (NO-ZVeff*NO0)/S_NO - ANO2 DQI CDS_NO = S_NO * exp(kt[O3]) DL1min = 2*SQRT(S(NO0))/60/CDS_NO ZVeff = (NOcal-NOcal0)/(NOcal-NOmeas) ANO2 = (NOymeas-NOy0)ZA/S_NO2 QNO2/NPN/HNO3 = S_NO2_NPN_HNO3 / CDS_NO March 15, 2004 EAS 4/8803

NO2 Specific Conversion for NOx Typical Data Quality Achieved Comm NO NOy NOx NO T (s) <1 <1 <1 60 DL1min (ppb) 0.003 0.5 0.5 0.075 DL30min (ppb) 0.0005 0.1 0.1 0.01 P (%) 10 15 15 >10 A (%) 15 20 20 >15 March 15, 2004 EAS 4/8803

SO2 Method: UV-Fluorescence Pulsed source 190-320 nm Fluorescence 320-380 nm March 15, 2004 EAS 4/8803

SO2 Analyzer Setup March 15, 2004 EAS 4/8803

SO2 Analyzer Operation SPAN: Standard addition every 12 h. ZTeff CHECK: Zero mode on top of SPAN every 24 h. ZERO: Instrument background or baseline every hour. March 15, 2004 EAS 4/8803

SO2 Signal Evaluation & Data Reduction Identify instrument baseline from zero modes SO2,0 Correct for zero trap efficiency < 100%: SO2,0* = SO20 / ZTeff – SO2ipol * (1/ZTeff-1) Interpolate between SO2,0* over the data set: SO2,0*ipol Subtract corrected baseline from amb signal: SO2net = SO2raw – SO2,0*ipol Identify instrument span from cal modes SO2span Determine instrument sensitivities (ppb/Vdc): SO2sens = Fcal/Ftot * [SO2cal] / SO2span Interpolate between SO2sens over the data set: SO2sensipol Determine final SO2 mixing ratio (ppb): SO2 = SO2net * SO2sensipol Determine SO2 data quality indicators: Lower Detection Limit (ppb) DL = t * STD(SO20*) * AVG(SO2sens) Zero Trap Efficiency (%) ZTeff = (SO2span – SO2span0) / (SO2span – SO20) Precision (%) P = t * STD(SO2sens) / AVG(SO2sens) *100 Accuracy (%) A = (slope {lin regress multi-pt cal} – 1) *100 March 15, 2004 EAS 4/8803

SO2 Data Quality Typically Achieved Commercial T (s) 45 60 DL1min (ppb) 0.05 0.1 DL30min (ppb) 0.01 0.02 P (%) 6 >10 A (%) 15 >20 March 15, 2004 EAS 4/8803

Emissions/AQ Trends: CO Sources (2001) Emissions Potential Risks and Effects Blood-O2 deficiency Cardiovascular (angina pectoris) Visual, neurological impairment Role in P(O3) via HOx cycle (slow) AQ March 15, 2004 EAS 4/8803

CO Method: IR-Absorption I = I0 e-e c l insulation T Thermo-electrically cooled PbSe 4.7 mm 30 Hz 360 Hz modulation 16 m March 15, 2004 EAS 4/8803

CO Analyzer Setup March 15, 2004 EAS 4/8803

CO Analyzer Operation SPAN: Standard addition every 24 h. ZTeff CHECK: Zero mode on top of SPAN every 24 h. ZERO: Instrument background or baseline every 12 minutes. March 15, 2004 EAS 4/8803

CO Signal Evaluation & Data Reduction Identify instrument baseline from zero modes CO0 Correct for zero trap efficiency < 100%: CO0* = CO0 / ZTeff – COipol * (1/ZTeff -1) Interpolate between CO0* over the data set: CO0*ipol Subtract corrected baseline from amb signal: COnet = COraw – CO0*ipol Identify instrument span from cal modes COspan Determine instrument sensitivities (ppb/Vdc): COsens = Fcal/Ftot * [COcal] / COspan Interpolate between COsens over the data set: COsensipol Determine final CO mixing ratio (ppb): CO = COnet * COsensipol Determine CO data quality indicators: Lower Detection Limit (ppb) DL = t * STD(CO0*) * AVG(COsens) Zero Trap Efficiency (%) ZTeff = (COspan – COspan0) / (COspan – CO0) Precision (%) P = t * STD(COsens) / AVG(COsens) *100 Accuracy (%) A = (slope {lin regress multi-pt cal} – 1) *100 March 15, 2004 EAS 4/8803

CO Data Quality Typically Achieved Commercial T (s) 20 60 DL1min (ppb) 50 100 DL30min (ppb) 10 20 P (%) 8 >15 A (%) 12 >20 March 15, 2004 EAS 4/8803

CO Analyzer Setup at Rooftop Lab Sample IN during regular operation 400C MnO2 NV set so that ΔP(Tee-NO) in Sample mode = ΔP(Tee-NC) in Zero mode Tee IR A-Cell NO NC C ZT March 15, 2004 EAS 4/8803

CO Analyzer Calibration MnO2 NV set so that ΔP(Tee-NO) in Sample mode = ΔP(Tee-NC) in Zero mode Tee IR A-Cell NO NC C ZT Vent out during calibration Manual connect during calibration CO MFM 1425 ppmv in N2 10 sccm MFC 10 slm Zero Air March 15, 2004 EAS 4/8803

Lab Setup (to scale) March 15, 2004 EAS 4/8803

Cal Gas Dilution System Cal Gas MFM Zero Air MFC Tank Cal Gas Standard is (NIST certified) 1425 ppmv CO in N2 Generate and supply min 4 different nominal concentrations [COnom] = (Fcal*COtank) / (Fcal + FZA) Hold FZA = const, since [COZA] > 0 !! March 15, 2004 EAS 4/8803

CO Calibration Record and Evaluation D[COnom]1 D[COnom]2 D[COnom]3 COspan0 CO0 Determine: COsens = D[COnom] / DCOspan ZTeff = (COspan – COspan0) / (COspan – CO0) CO0* = CO0 / ZTeff – COipol * (1/ZTeff-1) COnet = COraw – CO0*ipol CO = COnet * COsensipol DL = t * STD(CO0*) * COsens P = t * STD(COsens) / AVG(COsens) *100 A = (slope {lin regress multi-pt cal} – 1) *100 March 15, 2004 EAS 4/8803

Student t values and Confident limits Assume normal distribution! N-1 degrees of freedom. 95 % confidence interval. March 15, 2004 EAS 4/8803