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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. [ABSTRACT FROM AUTHOR]

Abstract: By the reinforcement of the vehicle emission reduction requirement in Japan, the nitrogen oxides (NOx) concentration in a roadside atmosphere decreased clearly recently. However, the ambient nitrogen dioxide (NO2) concentration does not show a substantial decrease. For the forecast of the improvement of the roadside NO2 by the motor vehicle emission regulation, we have been developing a roadside air quality simulation model. The chemical reactions of nitrogen oxide (NO) oxidation with ozone (O3), photodissociation of NO2, and O3 formation were included in this model. This study was carried out to clarify the NO2 behavior near roadside. Involving a spatial distribution of O3 concentration measurement, temporal and spatial variation of NO and NO2 was measured by the devices of chemiluminescence method which were prepared for each species. Concentration change was measured at the same time in four sites every 1 s to pay attention to a percentage of NO2/NOx which varied from route neighborhood to lee side way. The air flow of each sites was monitored by the ultrasonic 3D anemometer. The effect of NO2 concentration change due to the air stagnation or background ozone concentration was evaluated. From the cycle variation of potential ozone (PO) concentration as a function of the elapsed time of the traffic signal, the direct exhaust NO2 was estimated, and, around Noge intersection of Ring 8, Tokyo, 7.3% was obtained as primary NO2 fraction from vehicles. During an advection from the curbside site (0 m) to the 20 m remote site, more than 40% of NO oxidized and generate NO2 at 10 m height. At 3 m height, 7% of NO2 was generated and O3 was consumed in same quantity at the same time. [Copyright &y& Elsevier]

We report the results of year-long PM2.5 (particulate matter less than 2.5 µm in diameter) simulations over Northeast Asia for the base year of 2013 under the framework of the Long-range Transboundary Air Pollutants in Northeast Asia (LTP) project. LTP is a tripartite project launched by China, Japan, and Korea for cooperative monitoring and modeling of the long-range transport (LRT) of air pollutants. In the modeling aspect in the LTP project, each country's modeling group employs its own original air quality model and options. The three regional air quality models employed by the modeling groups are WRF-CAMx, NHM-RAQM2, and WRF-CMAQ. PM2.5 concentrations were simulated in remote exit-and-entrance areas associated with the LRT process over China, Japan, and Korea. The results showed apparent bias that remains unexplored due to a series of uncertainties from emission estimates and inherent model limitations. The simulated PM10 levels at seven remote exit-and-entrance sites were underestimated with the normalized mean bias of 0.4 ± 0.2. Among the four chemical components of PM2.5 (SO42−, NO3−, organic carbon (OC), and elemental carbon (EC)), the largest inter-model variability was in OC, with the second largest discrepancy in NO3−. Our simulation results also indicated that under considerable SO42− levels, favorable environments for ammonium nitrate formation were found in exit-and-entrance areas between China and Korea, and gas-aerosol partitioning for semi-volatile species of ammonium nitrate could be fully achieved prior to arrival at the entrance areas. Other chemical characteristics, including NO3−/SO42− and OC/EC ratios, are discussed to diagnose the LRT characteristics of PM2.5 in exit-and-entrance areas associated with transboundary transport over China, Japan, and Korea. [ABSTRACT FROM AUTHOR]