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Evidence for an increase in the ozone photochemical lifetime in the eastern United States using a regional air quality model
Author(s) -
Goldberg Daniel L.,
Vinciguerra Timothy P.,
Hosley Kyle M.,
Loughner Christopher P.,
Canty Timothy P.,
Salawitch Ross J.,
Dickerson Russell R.
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023930
Subject(s) - ozone , air quality index , atmospheric sciences , environmental science , hydroperoxyl , pollutant , photochemistry , chemistry , meteorology , radical , geography , physics , organic chemistry
Measures to control surface ozone rely on quantifying production attributable to local versus regional (upwind) emissions. Here we simulate the relative contribution of local (i.e., within a particular state) and regional sources of surface ozone in the eastern United States (66–94°W longitude) for July 2002, 2011, and 2018 using the Comprehensive Air‐quality Model with Extensions (CAMx). To determine how emissions and chemistry within the domain affect the production, loss, lifetime, and transport of trace gases, we initialize our model with identical boundary conditions in each simulation. We find that the photochemical lifetime of ozone has increased as emissions have decreased. The contribution of ozone from outside the domain (boundary condition ozone, BC O3 ) to local surface mixing ratios increases in an absolute sense by 1–2 ppbv between 2002 and 2018 due to the longer lifetime of ozone. The photochemical lifetime of ozone lengthens because the two primary gas phase sinks for odd oxygen (O x ≈ NO 2 + O 3 )—attack by hydroperoxyl radicals (HO 2 ) on ozone and formation of nitrate—weaken with decreasing pollutant emissions. The relative role of BC O3 will also increase. For example, BC O3 represents 34.5%, 38.8%, and 43.6% of surface ozone in the Baltimore, MD, region during July 2002, 2011, and 2018 means, respectively. This unintended consequence of air quality regulation impacts attainment of the National Ambient Air Quality Standard for surface ozone because the spatial and temporal scales of photochemical smog increase; the influence of pollutants transported between states and into the eastern U.S. will likely play a greater role in the future.