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Abstract
Three modeling approaches, the U.S. Environmental Protection Agency’s (EPA) Community Multiscale Air Quality (CMAQ) zero-out, the Comprehensive Air quality Model with extensions (CAMx) zero-out, and the CAMx probing tools ozone source apportionment tool (OSAT), were used to project the contributions of various source categories to future year design values for summer 8-hr average ozone concentrations at selected U.S. monitors. The CMAQ and CAMx zero-out or brute-force approaches predicted generally similar contributions for most of the source categories, with some small differences. One of the important findings from this study was that both the CMAQ and CAMx zero-out approaches tended to apportion a larger contribution to the “other” category than the OSAT approach. For the OSAT approach, this category is the difference between the total emissions and the sum of the tracked emissions and consists of non-U.S. emissions. For the zero-out approach, it also includes the effects of nonlinearities in the system because the sum of the sensitivities of all sources is not necessarily equal to the sum of their contributions in a nonperturbed environment. The study illustrates the strengths and weaknesses of source apportionment approaches, such as OSAT, and source sensitivity approaches, such as zero-out. The OSAT approach is suitable for studying source contributions, whereas the zero-out approach is suitable for studying response to emission changes. Future year design values of summer 8-hr average ozone concentrations were projected to decrease at all the selected monitors for all the simulations in each city, except at the downtown Los Angeles monitor. Both the CMAQ and CAMx results showed all modeled locations project attainment in 2018 and 2030 to the current National Ambient Air Quality Standards (NAAQS) level of 75 ppb, except the selected Los Angeles monitor in 2018 and the selected San Bernardino monitor in 2018 and 2030.
Implications:
This study illustrates the strengths and weaknesses of three modeling approaches, CMAQ zero-out, CAMx zero-out, and OSAT to project contributions of various source categories to future year design values for summer 8-hr average ozone concentrations at selected U.S. monitors. The OSAT approach is suitable for studying source contributions, whereas the zero-out approach is suitable for studying response to emission changes. Future year design values of summer 8-hr average ozone concentrations were projected to decrease, except at the downtown Los Angeles monitor. Comparing projections with the current NAAQS (75 ppb) show attainment everywhere, except two locations in 2018 and one location in 2030.
Additional information
Notes on contributors
Susan Collet
Susan Collet is a senior principal engineer and Hiroaki Minoura is an executive engineer at Toyota Motor Engineering and Manufacturing, North America, Inc., in Ann Arbor, MI.
Hiroaki Minoura
Susan Collet is a senior principal engineer and Hiroaki Minoura is an executive engineer at Toyota Motor Engineering and Manufacturing, North America, Inc., in Ann Arbor, MI.
Toru Kidokoro
Toru Kidokoro is a group manager, Yukihiro Sonoda is a general manager, and Yukio Kinugasa is a professional partner at Toyota Motor Corporation in Shizuoka, Japan.
Yukihiro Sonoda
Toru Kidokoro is a group manager, Yukihiro Sonoda is a general manager, and Yukio Kinugasa is a professional partner at Toyota Motor Corporation in Shizuoka, Japan.
Yukio Kinugasa
Toru Kidokoro is a group manager, Yukihiro Sonoda is a general manager, and Yukio Kinugasa is a professional partner at Toyota Motor Corporation in Shizuoka, Japan.
Prakash Karamchandani
Prakash Karamchandani is a senior manager, Allison DenBleyker and Jaegun Jung are senior associate managers, and Jeremiah Johnson and Tejas Shah are managers at ENVIRON International Corporation in Novato, CA.
Jeremiah Johnson
Prakash Karamchandani is a senior manager, Allison DenBleyker and Jaegun Jung are senior associate managers, and Jeremiah Johnson and Tejas Shah are managers at ENVIRON International Corporation in Novato, CA.
Tejas Shah
Prakash Karamchandani is a senior manager, Allison DenBleyker and Jaegun Jung are senior associate managers, and Jeremiah Johnson and Tejas Shah are managers at ENVIRON International Corporation in Novato, CA.
Jaegun Jung
Prakash Karamchandani is a senior manager, Allison DenBleyker and Jaegun Jung are senior associate managers, and Jeremiah Johnson and Tejas Shah are managers at ENVIRON International Corporation in Novato, CA.
Allison DenBleyker
Prakash Karamchandani is a senior manager, Allison DenBleyker and Jaegun Jung are senior associate managers, and Jeremiah Johnson and Tejas Shah are managers at ENVIRON International Corporation in Novato, CA.