The Relationships Between NO_x, NO_y and Ozone

Introduction
Monitoring Issues
Definitions
Analyses Using NO_x, NO_y, and Ozone Data
Summary of Correlation Methods
Indicator Methods
Observational-based Modeling: MAPPER/SPA
What is MAPPER?
Smog Production Algorithms
Modifications by Blanchard et al.
Other Techniques
Summary
References

• Emission control strategies are based on assessments of whether an area is "VOC-limited" or "NO_x-limited."
• No single analysis should form the basis for these decisions. Rather, several analyses, plus modeling, should provide concurrent evidence.
• This section explores analytical techniques which use NO_x, NO_y, ozone, and other species data.

• Most NO_x instruments are biased high, due to PAN and HNO₃ interferences.
• Urban to rural gradients are not characterized by current networks; heavy urban emphasis.
• Micro-siting issues; large influence of fresh NO_x emissions?

E = Extent of reaction
HCHO = Formaldehyde
H₂O₂ = Hydrogen peroxide
HNO₃ = Nitric acid
NMHC = Non-methane hydrocarbons
NMOC = Non-methane organic compounds (NMHC+carbonyl compounds)
NO_x = NO + NO₂ + poorly defined fraction of other NO_y species (given conventional analyzers)
NO_y = NO_x + HNO₃ + organic nitrates + inorganic nitrates = NO_x + NO_z
NO_z = Oxidation products of NO_x = NO_y ´ (1 - NO_x/NO_y)
ODM = Observation-driven Method
PAN = Peroxyacetylnitrate
Photochemical Age = Fraction of initial NO_x emissions that have been photooxidized = products/total = NO_z/NO_y
=1 - NO_x/NO_y
SP = Smog produced
SPA = Smog production algorithm
UAM = Urban Airshed Model
VOC = Volatile organic compounds

Examine patterns of ozone, NO, NO_x, and NO_y data using time series, scatter plots, and correlations:

• The difference between NO_y and NO_x at a site may vary over the course of the day.
• Positive correlations have been observed between ozone and NO_y or NO_z under some conditions.
• Ozone production efficiency may be examined with plots of ozone and photochemical age.

 Ozone with NO_y

• Good correlation if NO_x-limited
• Poor correlation if VOC-limited

Ozone with NO_z

• If slope > about 8, NO_x-limited
• If slope < about 5, VOC-limited

Objectives:

• Identifying spatial and temporal characteristics of VOC-limited and NO_x-limited conditions.
• Corroborating emission-based model results.
• Assisting monitoring network design.

Topics:

• What is MAPPER?
• Review of the smog production algorithm (SPA).
• MAPPER/model bi-directional control strategy evaluation.
• Example application.

• Software (PC-Windows) that estimates "relative" degree of NO_x- and VOC-limiting conditions, based on hourly ozone and NO_x (or NO_y) measurements.
• Original motivation to develop observational technique more robust than VOC/NO_x ratios.
• Developed by ENVAIR, originally funded by EPA and subsequently by API (Blanchard et al., 1993a, 1993b, 1994a, 1994b).

• The algorithm was developed by Graham Johnson; derived empirically from smog chamber data.
• The purpose is to determine ozone formation sensitivity to changes in NO_x concentrations.
• Ozone, NO, and NO_x (or NO_y) concentrations are used to compute Smog Produced and Extent of Reaction:

  SP(t) = O₃(t) - O₃(0) + NO(0) - NO(t)
  smog = ozone produced + oxidized NO

  SP_max = b (NO_x(i))
  Maximum smog produced µ NO_x inputs

  E = SP(t) / SP_max
  As E ® 1, enter NO_x-limited regime.
  As E > 0.7, enter transition.
  As E ® 0, enter VOC-limited regime.

• SP responds linearly to cumulative light flux; consequently accounting for the NO-ozone co-dependence.
• SPA is consistent with fundamental atmospheric chemistry processes: dSP/dt µ k _RO2 [NO]

• Adapted/fitted SPA to U.S. smog chamber data and box model chemical mechanism simulations by Blanchard et al. (1993a, 1993b, 1994a, 1994b).
• Revised SPA:

   SP_max = b (NO_x(i))^2/3

  SP(t) = O₃(t) + DO₃(t) - O₃(0) + NO(0) - NO(t)

  NO_x(0) (emitted NO_x) = NO_y(t) + DNO_y(t)
  DO₃; DNO_y = equivalent concentration due to deposition loss
  E = SP(t)/SP_max = f(measured O₃, NO, NO_y, or NO_x^*)

  ^* equivalent form based on NO_x

SP_max versus initial NO_x concentration for UNC, SAPRC, and CSIRO chamber experiments that utilized VOC mixtures and that reached SP_max (Blanchard et al., 1994a). The regression was carried out as log (SP_max) versus log [NO_x(0)] and the regression parameters were converted back to concentration units. The solid line is the regression line, as converted to concentration units. The dashed lines are the 95 percent confidence intevals for the regression.

SP_max versus initial NO_x computed using a box model and carbon bond mechanism (CBM-4, Gery et al., 1989) (Blanchard et al., 1994a). The simulation conditions included: urban average NMOC composition, initial NMOC of 2 to 5 ppmC, initial NO_x of 1 to 30 ppb, initial NO/NO_x of 0.95, Los Angeles latitude, June 21, 0600 PST, 1000 m mixing height, 298 K, no deposition.

Example of smog prouction algorithm MAPPER output from 1990 San Joaquin Valley Air Quality Study data collected on August 6, 1990 (Blanchard, 1997)

• Observational-based model developed by Cardelino and Chameides (1995).
• Requires hourly speciated hydrocarbon, NO, CO, and ozone concentrations as well as temperature, relative humidity, and mixing height.

• These analyses provide information which assist in the decisions on which species are the most important to ozone formation and begin to address the question of NO_x versus hydrocarbon emission controls.

Aneja V.P. and Das M. (1994) Correlation of ozone and meteorology with hydrogen peroxide in urban and rural regions of North Carolina. J. Appl. Meteorol. 34, 1890-1897.

Blanchard C.L. (1997) Personal communication.

Blanchard C.L., Roth P.M., and Jeffries H.E. (1993a) Continuing development of a methodology for assessing preferences for reductions in VOC versus NO_x emissions in nonattainment areas. Paper presented at the Air & Waste Management Association's Specialty Conference on Regional Photochemical Measurement and Modeling Studies, San Diego, CA, November 8-12.

Blanchard C.L., Roth P.M., and Jeffries H.E. (1993b) Spatial mapping of preferred strategies for reducing ambient ozone concentrations nationwide. Paper no. 93-TA-37A.04 presented at the Air & Waste Management Association's 86th Annual Meeting & Exhibition, Denver, CO, June 13-18.

Blanchard C.L., Lurmann F.W., Korc M.E., and Roth P.M. (1994a) The use of ambient data to corroborate analyses of ozone control strategies. Final report prepared for the U.S. Environmental Protection Agency, Research Triangle Park, NC by Sonoma Technology, Inc., Santa Rosa, CA and Envair, San Anselmo, CA, STI-94030-1433-FR, Contract No. 68D30020, December.

Blanchard C.L., Roberts P.T., Chinkin L.R., and Roth P.M. (1994b) Application of smog production (sp) algorithms to the Coastal Oxidant Assessment for Southeast Texas (COAST) data. Final report prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC by Envair, Albany, CA and Sonoma Technology, Inc., Santa Rosa, CA, STI-94080-1454-FR, Work Assignment 8-94, EPA Contract No. 68D30020, December.

Bottenheim J.W. and Sirois A. (1996) Long-term daily mean mixing ratios of O₃, PAN, HNO₃, and particle nitrate at a rural location in eastern Canada: relationships and implied ozone production efficiency. J. Geophys. Res. 191, 4189-4204.

Cardelino C.A. and Chameides W.L. (1995) An observation-based model for analyzing ozone precursor relationships in the urban atmosphere. J. Air & Waste Manag. Assoc. 45, 161-180.

Chang T.Y. and Suzio M.J. (1995) Assessing ozone-precursor relationships based on a smog production model and ambient data. J. Air & Waste Manag. Assoc. 45, 20-28.

Gery M.W., Whitten G.Z., Killus J.P., and Dodge M.C. (1989) A photochemical kinetics mechanism for urban and regional scale computer modeling. J. Geophys. Res. 94, 925-12.

Hartsell B.E., Aneja V.P., and Lonneman W.A. (1994) Relationships between peroxyacetyl nitrate, O₃, and NO_y at the rural southern oxidants study site in central Piedmont, North Carolina, site SONIA. J. Geophys. Res. 99, 21033-21041.

Hastie D.R., Shepson P.B., Reid N., Roussel P.B., and Melo O.T. (1996) Summertime NO_x, NO_y, and ozone at a site in rural Ontario. Atmos. Environ. 30, 2157-2165.

Jacob D.J., Horowitz L.W., Munger J.W., Heikes B.G., Dickerson R.R., Artz R.S., and Keene W.C. (1995) Seasonal transition from NO_x to hydrocarbon-limited conditions for ozone production over the eastern United States in September. J. Geophys. Res. 100, 9315-9324.

 Johnson G.M. (1984) A simple model for predicting the ozone concentration of ambient air. In Proceedings from the 8th International Clean Air Conference, Melbourne, Australia, May 2, pp. 715-731.

Johnson G.M. and Azzi M. (1992) Notes on the derivation: the integrated empirical rate model (V2.2). Report prepared by CSIRO Division of Coal and Energy Technology, North Ryde, NSW, Australia.

Johnson G.M. and Quigley S.M. (1989) A universal monitor for photochemical smog. Paper No. 89-29.8 presented at the 82nd Air & Waste Management Association Annual Meeting and Exhibition, Anaheim, CA, June 25-30.

Kelly T.J., Ward G.F., and Satola J. (1995) A comparison of NO_y and conventional "NO_x" measurements at a rural site in Pennsylvania. Paper presented at the Air & Waste Management Association and U.S. Environmental Protection Agency Measurement of Toxic and Related Air Pollutants Conference, Research Triangle Park, NC, May 16-19.

Koike M., Kondo Y., Kawakami S., Singh H.B., and Ziereis H. (1996) Ratios of reactive nitrogen species over the Pacific during PEM-West A. J. Geophys. Res. 101, 1829-1851.

Korc M.E., Jones C.M., Chinkin L.R., Main H.H., Roberts P.T., and Blanchard C. (1995) Use of PAMS data to evaluate the Texas coast emission inventory. Final report prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC by Sonoma Technology, Inc., Santa Rosa, CA, Work assignment 2-95, EPA Contract No. 68D30020, STI-94520-1558-FR, December.

Milford J.B., Gao D., Sillman S., Blossey P., and Russell A.G. (1994) Total reactive nitrogen (NO_y) as an indicator of the sensitivity of ozone to reductions in hydrocarbon and NO_x emissions. J. Geophys. Res. 99, 3533-3542.

National Research Council (1991) Rethinking the Ozone Problem in Urban and Regional Air Pollution. National Academy Press, Washington, D.C.

Olszyna K.J., Bailey E.M., Simonaitis R., and Meagher J.F. (1994) O₃ and NO_y relationships at a rural site. J. Geophys. Res. 99, 14557-14563.

Sillman S. (1995) The use of NO_y, H₂O₂, and HNO₃ as indicators for ozone-NO_x-hydrocarbon sensitivity in urban locations. J. Geophys. Res. 100, 14175-14188.

Singh H.B. et al. (1996) Reactive nitrogen and ozone over the western Pacific: distribution, partitioning, and sources. J. Geophys. Res. 101, 1793-1808.

Trainer M., Parrish D.D., Buhr M.P., Norton R.B., Fehsenfeld F.C., Anlauf K.G., Bottenheim J.W., Tang Y.Z., Wiebe H.A., Roberts J.M., Tanner R.L., Newman L., Bowersox V.C., Meagher J.F., Olszyna K.J., Rodgers M.O., Wang T., Berresheim H., Demerjian K.L., and Roychowdhury U.K. (1993) Correlation of ozone with NO_y in photochemically aged air. J. Geophys. Res. 98, 2917-2925.