1. 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

2. Physical and Chemical Measuring Principles
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3. Applied Measuring Techniques
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4. Photometry: IR Absorption Bands
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5. Photometry: UV Absorption Spectra
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EAS 4/8803

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

7. NO/NOx/NOy Method: Chemiluminescence
From inlet box
Excess O3 C NC NO
Chemi-lumi-nescence
max 1200 nm
Reaction Vessel
Zero Volume
O3 Trap
PMT HV Hz
NO + O NO2* + O2
NO + O 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

8. 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

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

10. SO2 Method: UV-Fluorescence
Pulsed source nm
Fluorescence nm
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11. SO2 Analyzer Setup
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12. 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
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13. 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

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

15. 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

16. 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

17. CO Analyzer Setup
March 15, 2004
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18. 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

19. 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

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

21. 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

22. 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
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23. Lab Setup (to scale)
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24. 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

25. 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

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