Evaluation of light-duty vehicle mobile source regulations on ozone concentration trends in 2018 and 2030 in the western and eastern United States

Abstract

To improve U.S. air quality, there are many regulations on-the-way (OTW) and on-the-books (OTB), including mobile source California Low Emission Vehicle third generation (LEV III) and federal Tier 3 standards. This study explores the effects of those regulations by using the U.S. Environmental Protection Agency's (EPA) Community Multiscale Air Quality (CMAQ) model for 8-hr ozone concentrations in the western and eastern United States in the years 2018 and 2030 during a month with typical high ozone concentrations, July. Alterations in pollutant emissions can be due to technological improvements, regulatory amendments, and changes in growth. In order to project emission rates for future years, the impacts of all of these factors were estimated. This study emphasizes the potential light-duty vehicle emission changes by year to predict ozone levels. The results of this study show that most areas have decreases in 8-hr ozone concentrations in the year 2030, although there are some areas with increased concentrations. Additionally, there are areas with 8-hr ozone concentrations greater than the current U.S. National Ambient Air Quality Standard level, which is 75 ppb.Implications: To improve U.S. air quality, many regulations are on the way and on the books, including mobile source California LEV III and federal Tier 3 standards. This study explores the effects of those regulations for 8-hr ozone concentrations in the western and eastern United States in the years 2018 and 2030. The results of this study show that most areas have decreases in 8-hr ozone concentrations in 2030, although there are some areas with increased concentrations. Additionally, there are areas with 8-hr ozone concentrations greater than the current U.S. National Ambient Air Quality Standard level.

Future year ozone source attribution modeling studies for the eastern and western United States

“…CMAQ simulations for the month of July for the base year 2008 were already available from the previous study described in Collet et al (2014). Model evaluation results for the same period have also been presented in Collet et al (2014). As in the previous study, version 4.7.1 of CMAQ (released in June 2010) was used with the recommended options for the various CMAQ science modules.…”

“…This study builds upon the previous study of Collet et al (2014), in which projected ozone outcomes resulting from implementing air quality regulations in the U.S. that are on-thebooks or on-the-way were calculated. The previous study was done by developing anthropogenic emission inventories for 2018 and 2030, and Community Multiscale Air Quality (CMAQ) simulations were conducted to estimate future year ambient concentrations of ozone for a summer month (July) using 2008 meteorology and natural emissions in the eastern and western U.S.…”

“…The California Air Resources Board (CARB) has approved the Low Emission Vehicle third-generation (LEV III) standards, and the U.S. Environmental Protection Agency (EPA) adopted similar requirements. The expected changes to air quality due to these mobile source requirements were modeled and described in a study by Collet et al (2014) and in another study by Vijayaraghavan et al (2012). Collet et al (2012) used the Comprehensive Air quality Model with extensions (CAMx) model (version 4.6) (Byun and Schere, 2006) to compare the air quality impacts in California's South Coast Air Basin (SoCAB) of emissions from passenger cars and light-duty trucks under the California Low Emission Vehicle II (LEV II) standards with those from a control scenario that was anticipated in 2008 to become LEV III.…”

Future-Year Ozone Isopleths for South Coast, San Joaquin Valley, and Maryland

“…In previous modeling studies, Collet et al [12,13] simulated the entire contiguous U.S. (continental U.S. or CONUS) domain (396 vertical by 246 horizontal grid cells) at 12-km resolution with the CAMx 6.4. For this study, a different approach was adopted because the development of ozone isopleths relating ozone responses to NO x and VOC emissions changes required several tens of emissions scenario simulations to be conducted.…”

Future year ozone source attribution modeling study using CMAQ-ISAM

“…Thus, for this study, only a summer month (July) simulation for ozone was performed with CMAQ-ISAM. However, full base year and future year simulations with CMAQ without ISAM were conducted to develop future year design values of ozone for comparison with CAMx-predicted future year design values (Collet et al 2014b).…”