1. Field Methods of Monitoring Atmospheric Systems
Chemical Methods: Chemiluminescence, Chemical Amplification, Electrochemistry and Derivatization
Copyright © 2006 by DBS

2. Introduction Chemical conversion techniques
Chemiluminescence – light production by chemical reaction
‘scrubbing’ into solution
Electrochemical
Measurements
Routine measurements of urban NOx
High-altitude aircraft studies of O3 depletion
Electrochemical sondes (Light-weight instruments) used to measure spatial and temporal distribution of O3
Eddy fluxes of O3 and isoprene from trees
Chemical measurements of radical species HO2 and RO2

3. O3 (Heterogeneous Chemiluminescence)
Reaction with dyes
Excited product transfers energy to fluorescent dye (liquid or gel)
Early years (luminol and rhodamine-B)
Regener, 1960; Hodgeson et al, 1970
Used to measure 30 profiles of O3 concentration (balloons)
Hilsenrath et al, 1969
Stevens and O’Keefe, 1970

4. O3 (Heterogeneous Chemiluminescence)
Since mid-1980s
Commercial instruments using flowing Eosin-Y on fiber pad (Ray et al, 1986)
Coumarin-47 on silica gel (Schurath et al, 1991)
Summary
High specificity, low cost, low weight, low power
Avoid use of compressed hazardous gases (used in homogeneous techniques)
High sensitivity and fast response time – most useful for flux measurements and use in aircraft

5. O3 via Electrochemistry
Ozone sondes
O3 profiles up to 35 km
2KI + O3 + H2O → I2 + O2 + 2KOH
I2 is converted back to I- at the cathode
2 types
Brewer-Mast cell
Electrochemical Concentration Cell (ECC)
Tropospheric O3 not well sampled by satellites
Komhyr et al., 1995

6. Nitrogen Compounds (NO, NO2, NOy) via Chemiluminescence with O3
Reactive N compound measurement is based on the NO + O3 reaction
NO + O3 → NO2* + O2
NO2* → NO2 + hν
Where λ = nm (Clyne et al.,1964)

7. Measurement of NO
O3 (generated in instrument) is mixed with sample and light emission measured with photomultiplier
Polished gold plated reaction vessel
Small size
Detection limit: 1-2 pptv
Discovery that thunderstorms inject lightning produced NO into upper troposphere
Affecting O3 levels downstream
Ridley et al., 2004

8. Measurement of NO2
Total N-oxides (NOx): Analyzed by thermal or photolytic conversion (more specific) of NO2 to NO
Nitrogen Dioxide (NO2): Difference between NOx – NO
Requires scrubber for NH3
Detection limit: 10 ppb (18 μg m-3)
Interferents convert to NO2 under heat but do not convert via photolysis as strongly

9. Boubel et al., 1994

10. Measurement of Total Reactive N (NOy)
NO, NO2, NO3, N2O5, HONO, HNO3, HO2NO2, ClONO2, PANs
Convert all of the above to NO but not NH3, N2O, HCN
Gold catalyst reduces NOy to NO and CO measured via chemiluminescence with O3
Forward inlet trace
NOy (HNO3) particulate spikes
Aft inlet trace: NOy (HNO3)

11. Routine NOx Monitoring
Heard, 2006
Routine NOx Monitoring
Maxima during rush-hour reflects major source
Diurnal cycle
Source: Heard, 2006
Spatial
Decadal cycle

12. Ozone via Homogeneous Chemiluminescence
Opposite of NO method
Used to make eddy-correlation flux measurements of O3
Contributions of chemistry and transport to O3 budget may be measured (Lenschow et al., 1981)
O3 compared to NO
O3 is found at much larger concentration than NO
NO (bottle) much easier reagent to provide than O3 (discharge)
Smaller reaction vessels are possible for O3 since reagent NO is pure compared to O3

13. Peroxides, HCHO, HONO via Liquid Techniques
H2O2 via dissolution and chemiluminescence
Products of photochemistry (indicator species)
Reservoirs of odd H radicals
‘Scrubbing’ techniques
Extracted into aqueous solution of luminol and CuSO4
Detection via PMT
Detction limit: 1 ppbv (useful for polluted areas)
Kok et al., 1978

14. Peroxides via dissolution, derivatization, and fluorimetry
HCHO via dissolution, derivatization, and fluorimetry
HCHO via dissolution, derivatization, and HPLC
HONO via liquid techniques

15. Isoprene via O3 Chemiluminescence
Has largest flux of any reactive biogenic HC
Chemiluminescent reaction with O3
Diurnal cycle is driven by solar radiation
Guenther and Hills, 1998

16. Peroxy Radicals via Chemical Amplification
HO2 and RO2 transfer O to NO to form NO2 wich photolyzes to liberate an O atom
O atom combines with O2 molecule to form O3
Trace gases → → RO2 → → CO2 + H2O
(many steps)
(CO, HC’s, VOC’s, HCFC’s)
(Peroxy radicals)
+ NO → NO2 + hv → NO + O
O + O2 → O3
Very complex!!!

17. PERCA – Peroxy Radicals by Chemical Amplification
Conversion of HO2 to NO2 using reagent NO followed by detection via luminol technique
HO2 + NO → OH + NO2
OH + CO → H + CO2
H + O2 + M → HO2 + M
OH is recycled back to OH2 to increase concentration of NO2
Cantrell et al., 1993

18. ROxMAS – ROx Mass Spectrometer
Using reagent NO and SO2, followed by CIMS detection of H2SO4
HO2 + NO → OH + NO2
OH + SO2 + M → HOSO2 + M
HOSO2 + O2→ SO3 + HO2
SO3 + 2H2O → H2SO4 + H2O
OH is recycled via reaction with SO2
H2SO4 detected by mass spectrometry
Advantage: Smaller background of H2SO4 compared to NO2
Hanke et al., 2002

19. Summary and Future Directions
RO2 measurement is ‘lumped’ would like speciation to define sources
Likewise with NOy
Use of LIF for NO2 when NO is a large fraction of NOx (upper tropsophere)
Use of in-service aircraft to validate satellite measurements

20. Further Reading Journal Articles
Clyne, M.A.A., Thrush, B.A., and Wayne, R.P. (1964) Kinetics of the chemiluminescent reaction between nitric oxide and ozone. Transactions of the Faraday Society, Vol. 60, pp
Fahey, D.W., et al. (2001) The detection of large HNO3-containing particles in the winter Arctic stratosphere. Science, Vol. 291, pp
Fontjin, A., Sabadell, A.J., and Ronco, R.J. (1970) Homogeneous chemiluminescent measurements of nitric oxide with ozone. Analytical Chemistry, Vol. 42, pp
Guenther, A.B., and Hills, A.J. (1998) Eddy covariance measurement of isoprene fluxes. Journal of Geophysical Research, Vol. 103 (D11), pp
Gusten, H., and Heinrich, G. (1996) On-line measurements of ozone surface fluxes: part I. Methodology and Instrumentation. Atmospheric Environment, Vol. 30, No. 6, pp
Hodgeson, J.A., Krost, K.J., O’Keefe, A.E., and Stevens, R.K. (1970) Chemiluminescent measurement of atmospheric ozone. Analytical Chemistry, Vol. 42, pp
Komhyr, W.D., Branes, R.A., Brothers, G.B., Lathrop, J.A., and Opperman, D.P. (1995) Electrochemical concentration cell ozonesonde performance evaluation during STOIC Journal of Geophysical Research, Vol. 100 (D5), pp
Lenschow, D.H., Pearson, R., Jr., and Stankow, B.B. (1981) Estimating the ozone eddy flux and mean concentration. Journal of Geophysical Research, Vol.86 (C8) pp
McKendry, I.G. et al. (1998)
Ray, J.D., Stedman, D.H., and Wendel, G.J. (1986) Fast chemiluminescent method for measurement of ambient ozone. Analytical Chemistry, Vol. 58, pp
Ridley, B.A., Carroll, M.A., and Greogory, G.L. (1987) Measurements of nitric oxide in the boundary layer and free troposphere over the Pacific Ocean. Journal of Geophysical Research, Vol. 92 (D2), pp
Ridley, B. et al. (2004) Florida thunderstorms: A faucet of reactive nitrogen to the upper troposphere. Journal of Geophysical Research, Vol. 109, D17305.
Schurath, U. et al. (1991)
Stevens, R.K., and O’Keefe, A.E. (1970) Modern aspects of air pollution monitoring. Analytical Chemistry, Vol. 42, pp. 143A-148A.
Stuhl, F. and Niki, H. (1970)
WMO (1998)

21. Books and General Reviews
Cantrell, C.A. (2003) Observation for chemistry (in situ), chemiluminescent techniques, in Encyclopedia of Atmospheric Sciences, Holton, J.R. et al. (eds), Academic Press, Vol. 4, pp
Clemitshaw, K.C. (2004) A review of instrumentation and measurement techniques for ground-based and airborne field studies of gas-phase tropospheric chemistry. Critical Reviews in Environmental Science and Technology, Vol. 34, pp
Settle, F.A. (ed.) (1997) Handbook of Instrumental techniques for Analytical Chemistry. Prectice Hall.