Chapter 2
Ozone in the Eastern United States:
Production Efficiency Variability Over
Time and Between Sources
Lucas R. F. Henneman, Huizhong Shen, Cong Liu, Yongtao Hu,
James A. Mulholland and Armistead G. Russell
Abstract The eastern United States has seen dramatic air pollution emissions reductions since the turn of the century. These emissions reductions have in turn been linked
to widespread reductions in ozone (O 3 )—between 2000 and 2016, the US EPA reports
a reduction in 4th highest mean daily annual 8-hr O 3 of 15% (from 82.3 to 69.6 ppb)
across 206 sites nationwide. Reductions, however, have not been spatially uniform or
linear with emissions reductions, and therefore motivate an investigation into spatial
and source-specific O 3 production efficiency (OPE). OPE is a measure of the number of O 3 molecules produced per emitted NO X (NO X = NO + NO 2 ) molecule. We
assess OPE using both model-based and empirical approaches. We modelled July
OPE in 2001 and 2011 using CMAQ-DDM version 5.0 with a 12 km resolution over
the eastern US. CMAQ-modelled OPE is taken as a ratio of electricity generating unit
and mobile source sensitivities, and controls for differences in O 3 and NO Z deposition rates. Measurements were taken from the SEARCH network, which reports
sub-daily observations of many gaseous and particulate species along with meteorological measurements at eight sites in the southeastern US. Using measurement data,
we stratified days based on their emissions-independent photochemical state, and
estimated OPE using a spline model to assess the relationship between O 3 and NO X
reaction products (denoted NO Z ). Both approaches yield an increase in OPE with
decreasing NO Z , indicating an increasing effectiveness at lowering O 3 for subsequent
NO X emissions reductions. Electricity generating unit OPEs are low near individual sources, but generally higher than on-road mobile source OPEs throughout the
domain, suggesting that further utility NO X emissions reductions will reduce regional
O 3 concentrations more efficiently than mobile source NO X emissions reductions.
L. R. F. Henneman (B)
Harvard TH Chan School of Public Health, 655 Huntington Avenue Building 2, 4th Floor, Boston,
MA 02115, USA
e-mail: henneman@hsph.harvard.edu
H. Shen · Y. Hu · J. A. Mulholland · A. G. Russell
Georgia Institute of Technology School of Civil and Environmental Engineering, 790 Atlantic
Drive, Atlanta, GA 30332-0355, USA
C. Liu
School of Energy and Environment, Southeast University, Nanjing, China
© Springer Nature Switzerland AG 2020
C. Mensink et al. (eds.), Air Pollution Modeling and its Application XXVI,
Springer Proceedings in Complexity,
https://doi.org/10.1007/978-3-030-22055-6_2
9
Ozone in the Eastern United States:
Production Efficiency Variability Over
Time and Between Sources
Lucas R. F. Henneman, Huizhong Shen, Cong Liu, Yongtao Hu,
James A. Mulholland and Armistead G. Russell
Abstract The eastern United States has seen dramatic air pollution emissions reductions since the turn of the century. These emissions reductions have in turn been linked
to widespread reductions in ozone (O 3 )—between 2000 and 2016, the US EPA reports
a reduction in 4th highest mean daily annual 8-hr O 3 of 15% (from 82.3 to 69.6 ppb)
across 206 sites nationwide. Reductions, however, have not been spatially uniform or
linear with emissions reductions, and therefore motivate an investigation into spatial
and source-specific O 3 production efficiency (OPE). OPE is a measure of the number of O 3 molecules produced per emitted NO X (NO X = NO + NO 2 ) molecule. We
assess OPE using both model-based and empirical approaches. We modelled July
OPE in 2001 and 2011 using CMAQ-DDM version 5.0 with a 12 km resolution over
the eastern US. CMAQ-modelled OPE is taken as a ratio of electricity generating unit
and mobile source sensitivities, and controls for differences in O 3 and NO Z deposition rates. Measurements were taken from the SEARCH network, which reports
sub-daily observations of many gaseous and particulate species along with meteorological measurements at eight sites in the southeastern US. Using measurement data,
we stratified days based on their emissions-independent photochemical state, and
estimated OPE using a spline model to assess the relationship between O 3 and NO X
reaction products (denoted NO Z ). Both approaches yield an increase in OPE with
decreasing NO Z , indicating an increasing effectiveness at lowering O 3 for subsequent
NO X emissions reductions. Electricity generating unit OPEs are low near individual sources, but generally higher than on-road mobile source OPEs throughout the
domain, suggesting that further utility NO X emissions reductions will reduce regional
O 3 concentrations more efficiently than mobile source NO X emissions reductions.
L. R. F. Henneman (B)
Harvard TH Chan School of Public Health, 655 Huntington Avenue Building 2, 4th Floor, Boston,
MA 02115, USA
e-mail: henneman@hsph.harvard.edu
H. Shen · Y. Hu · J. A. Mulholland · A. G. Russell
Georgia Institute of Technology School of Civil and Environmental Engineering, 790 Atlantic
Drive, Atlanta, GA 30332-0355, USA
C. Liu
School of Energy and Environment, Southeast University, Nanjing, China
© Springer Nature Switzerland AG 2020
C. Mensink et al. (eds.), Air Pollution Modeling and its Application XXVI,
Springer Proceedings in Complexity,
https://doi.org/10.1007/978-3-030-22055-6_2
9