Source apportionment of emissions from light-duty gasoline vehicles and other sources in the United States for ozone and particulate matter

ABSTRACT

Federal Tier 3 motor vehicle emission and fuel sulfur standards have been promulgated in the United States to help attain air quality standards for ozone and PM_2.5 (particulate matter with an aerodynamic diameter <2.5 μm). The authors modeled a standard similar to Tier 3 (a hypothetical nationwide implementation of the California Low Emission Vehicle [LEV] III standards) and prior Tier 2 standards for on-road gasoline-fueled light-duty vehicles (gLDVs) to assess incremental air quality benefits in the United States (U.S.) and the relative contributions of gLDVs and other major source categories to ozone and PM_2.5 in 2030. Strengthening Tier 2 to a Tier 3-like (LEV III) standard reduces the summertime monthly mean of daily maximum 8-hr average (MDA8) ozone in the eastern U.S. by up to 1.5 ppb (or 2%) and the maximum MDA8 ozone by up to 3.4 ppb (or 3%). Reducing gasoline sulfur content from 30 to 10 ppm is responsible for up to 0.3 ppb of the improvement in the monthly mean ozone and up to 0.8 ppb of the improvement in maximum ozone. Across four major urban areas—Atlanta, Detroit, Philadelphia, and St. Louis—gLDV contributions range from 5% to 9% and 3% to 6% of the summertime mean MDA8 ozone under Tier 2 and Tier 3, respectively, and from 7% to 11% and 3% to 7% of the maximum MDA8 ozone under Tier 2 and Tier 3, respectively. Monthly mean 24-hr PM_2.5 decreases by up to 0.5 μg/m³ (or 3%) in the eastern U.S. from Tier 2 to Tier 3, with about 0.1 μg/m³ of the reduction due to the lower gasoline sulfur content. At the four urban areas under the Tier 3 program, gLDV emissions contribute 3.4–5.0% and 1.7–2.4% of the winter and summer mean 24-hr PM_2.5, respectively, and 3.8–4.6% and 1.5–2.0% of the mean 24-hr PM_2.5 on days with elevated PM_2.5 in winter and summer, respectively.

Implications: Following U.S. Tier 3 emissions and fuel sulfur standards for gasoline-fueled passenger cars and light trucks, these vehicles are expected to contribute less than 6% of the summertime mean daily maximum 8-hr ozone and less than 7% and 4% of the winter and summer mean 24-hr PM_2.5 in the eastern U.S. in 2030. On days with elevated ozone or PM_2.5 at four major urban areas, these vehicles contribute less than 7% of ozone and less than 5% of PM_2.5, with sources outside North America and U.S. area source emissions constituting some of the main contributors to ozone and PM_2.5, respectively.

Supplemental Material

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Additional information

Funding

This work was supported by the Coordinating Research Council Atmospheric Impacts Committee under Project A-76-3.

Notes on contributors

Krish Vijayaraghavan

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Chris Lindhjem

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Bonyoung Koo

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Allison DenBleyker

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Edward Tai

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Tejas Shah

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Yesica Alvarez

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.

Greg Yarwood

Krish Vijayaraghavan and Chris Lindhjem are senior managers, Tejas Shah and Bonyoung Koo are managers, Edward Tai and Yesica Alvarez are associates, and Greg Yarwood is a principal at Ramboll Environ US Corporation, Novato, CA, USA. Allison DenBleyker is a staff engineer at Eastern Research Group, Boston, MA, USA.