EAS 4/8803: Experimental Methods in AQ

EAS 4/8803: Experimental Methods in AQWeek 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 O3Why 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)

EAS 4/8803

Physical and Chemical Measuring Principles

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Applied Measuring Techniques

EAS 4/8803

Photometry: IR Absorption Bands

EAS 4/8803

Photometry: UV Absorption Spectra

EAS 4/8803

NO/NOy Analyzer Inlet Box

EAS 4/8803

NO/NOx/NOy Method: Chemiluminescence

EAS 4/8803

NO/NOy Analyzer OperationSnoopNOy_cps: Photon counts per sNOyNO: NO measure modeNOy: NOy measure modeNOyNO0: NO zero modeNOy0: NOy zero modeSensitivities (cps/ppt)S_NO = (NOcal-NOipol)/[NOnom] S_NO2 =(NOyNO2cal-NOyipol)/[NO2nom]S_NPN=(NOyNPNcal-NOyipol)/[NPNnom]S_HNO3=(NOyHNO3cal-NOyipol)/[HNO3nom]MR CalculationNO (ppbv) = (NO-ZVeff*NO0)/S_NONOy (ppbv) = (NOy-ZVeff*(NOy0-NO0)-NO)/S_NO2 + (NO-ZVeff*NO0)/S_NO - ANO2DQICDS_NO = S_NO * exp(kt[O3])DL1min = 2*SQRT(S(NO0))/60/CDS_NOZVeff = (NOcal-NOcal0)/(NOcal-NOmeas)ANO2 = (NOymeas-NOy0)ZA/S_NO2QNO2/NPN/HNO3 = S_NO2_NPN_HNO3 / CDS_NO

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SO2 Method: UV-Fluorescence

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SO2 Analyzer Setup

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SO2 Analyzer OperationSPAN: Standard addition every 12 h.ZTeff CHECK: Zero mode on top of SPAN every 24 h.ZERO: Instrument background or baseline every hour.

EAS 4/8803

SO2 Signal Evaluation & Data Reduction Identify instrument baseline from zero modesSO2,0 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 modesSO2span 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 * SO2sensipolDetermine 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) *100Accuracy (%)A = (slope {lin regress multi-pt cal} 1) *100

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SO2 Data QualityTypically AchievedCommercialT (s)4560DL1min (ppb)0.050.1DL30min (ppb)0.010.02P (%)6 >10 A (%)15 >20

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Emissions/AQ Trends: COAQEmissionsSources (2001)Potential Risks and Effects Blood-O2 deficiency Cardiovascular (angina pectoris) Visual, neurological impairment Role in P(O3) via HOx cycle (slow)

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CO Method: IR-AbsorptionI = I0 e-e c l

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CO Analyzer Setup

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CO Analyzer OperationSPAN: Standard addition every 24 h.

ZTeff CHECK: Zero mode on top of SPAN every 24 h.ZERO: Instrument background or baseline every12 minutes.

EAS 4/8803

CO Signal Evaluation & Data Reduction Identify instrument baseline from zero modesCO0 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 modesCOspan 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 * COsensipolDetermine 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) *100Accuracy (%)A = (slope {lin regress multi-pt cal} 1) *100

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CO Data QualityTypically AchievedCommercialT (s)2060DL1min (ppb)50100DL30min (ppb)1020P (%)8 >15 A (%)12 >20

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CO Analyzer Setup at Rooftop Lab

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CO Analyzer CalibrationVent out during calibrationManual connect during calibration

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Lab Setup (to scale)

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Cal Gas Dilution SystemCal Gas MFM Zero Air MFCTank Cal Gas Standard is (NIST certified) 1425 ppmv CO in N2Generate and supply min 4 different nominal concentrations[COnom] = (Fcal*COtank) / (Fcal + FZA)Hold FZA = const, since [COZA] > 0 !!

EAS 4/8803

CO Calibration Record and EvaluationDetermine:COsens = D[COnom] / DCOspan ZTeff = (COspan COspan0) / (COspan CO0)CO0* = CO0 / ZTeff COipol * (1/ZTeff-1)COnet = COraw CO0*ipolCO = COnet * COsensipolDL = t * STD(CO0*) * COsensP = t * STD(COsens) / AVG(COsens) *100A = (slope {lin regress multi-pt cal} 1) *100

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Student t values and Confident limitsAssume normal distribution!N-1 degrees of freedom.95 % confidence interval.

EAS 4/8803