Ozone National Ambient Air Quality Research Articles

Emission Projections for the U.S. Environmental Protection Agency Section 812 Second Prospective Clean Air Act Cost/Benefit Analysis

Section 812 of the Clean Air Act Amendments (CAAA) of 1990 requires the U.S. Environmental Protection Agency (EPA) to perform periodic, comprehensive analyses of the total costs and total benefits of programs implemented pursuant to the CAAA. The first prospective analysis was completed in 1999. The second prospective analysis was initiated during 2005. The first step in the second prospective analysis was the development of base and projection year emission estimates that will be used to generate benefit estimates of CAAA programs. This paper describes the analysis, methods, and results of the recently completed emission projections. There are several unique features of this analysis. One is the use of consistent economic assumptions from the Department of Energy’s Annual Energy Outlook 2005 (AEO 2005) projections as the basis for estimating 2010 and 2020 emissions for all sectors. Another is the analysis of the different emissions paths for both with and without CAAA scenarios. Other features of this analysis include being the first EPA analysis that uses the 2002 National Emission Inventory files as the basis for making 48-state emission projections, incorporating control factor files from the Regional Planning Organizations (RPOs) that had completed emission projections at the time the analysis was performed, and modeling the emission benefits of the expected adoption of measures to meet the 8-hr ozone National Ambient Air Quality Standards (NAAQS), the Clean Air Visibility Rule, and the PM2.5 NAAQS. This analysis shows that the 1990 CAAA have produced significant reductions in criteria pollutant emissions since 1990 and that these emission reductions are expected to continue through 2020. CAAA provisions have reduced volatile organic compound (VOC) emissions by approximately 7 million t/yr by 2000, and are estimated to produce associated VOC emission reductions of 16.7 million t by 2020. Total oxides of nitrogen (NOx) emission reductions attributable to the CAAA are 5, 12, and 17 million t in 2000, 2010, and 2020, respectively. Sulfur dioxide (SO2) emission benefits during the study period are dominated by electricity-generating unit (EGU) SO2 emission reductions. These EGU emission benefits go from 7.5 million t reduced in 2000 to 15 million t reduced in 2020.

Long‐term probabilistic forecast of climate impact on air quality: Model development and t* distribution

Models are great tools to test ideas. Their usefulness, however, depends on their ability to simulate the current reality and to predict the future. In this study, I have derived a new t* distribution. I show that a statistical model based on the t* distribution of station temporal data is capable of predicting the probability of any future outcome to exceed a specific value using only the currently available sample statistics assuming a normal random variable. In an air quality management application the model has demonstrated categorically an average success rate of over 80% both in simulating the current ozone nonattainment areas and in forecasting the rate of future violation of the 8‐hour ozone National Ambient Air Quality Standards in the United States for up to 12 years. While the predictability of deterministic climate models is still limited by large uncertainties, the probabilistic forecast by this model provides a promising alternative in assessing the climate impact on environment for decades.

Adjoint Sensitivity Analysis of Ozone Nonattainment over the Continental United States

An application of the adjoint method in air quality management is demonstrated. We use a continental scale chemical transport model (STEM) to calculate the sensitivities of a nationwide U.S. ozone national ambient air quality standard (NAAQS) nonattainment metric to precursor emissions for the period July 1 to August 15, 2004. The model shows low bias and error (-4 and 24%, respectively), particularly for areas with high ozone concentrations. The nonattainment metric accounts for both 1-h and 8-h ozone standards, but is dominated by the 8-h exceedances (97% of the combined metric). Largest values of sensitivities are found to be with respect to emissions in the south and southeast U.S., Ohio River Valley, and California. When nonattainment sensitivities are integrated over the entire U.S., NOx emissions account for the largest contribution (62% of the total), followed by biogenic and anthropogenic VOCs (24% and 14%, respectively). For NOx emissions, point/area and mobile sources account for 54% and 46% of the total sensitivities, respectively. We also provide a state-by-state comparison for the nonattainment magnitude, nonattainment sensitivity, and emission magnitudes to explore the influence of interstate transport of ozone and its precursors, and policy implications of the results. Our analysis of the nationwide ozone nonattainment metric suggests that simple cap-and-trade programs may prove inadequate in achieving sought-after air quality objectives.

An Operational Assessment of the Application of the Relative Reduction Factors in the Demonstration of Attainment of the 8-Hr Ozone National Ambient Air Quality Standard

The U.S. Environmental Protection Agency in 1997 revised the 1-hr ozone (O3) National Ambient Air Quality Standard (NAAQS) to one based on an 8-hr average, resulting in potential nonattainment status for substantial portions of the eastern United States. The regulatory process provides for the development of a state implementation plan that includes a demonstration that the projected future O3 concentrations will be at or below the NAAQS based on photochemical modeling and analytical techniques. In this study, four photochemical modeling systems, based on two photochemical models, Community Model for Air Quality and the Comprehensive Air Quality Model with extensions, and two emissions processing models, Sparse Matrix Optimization Kernel for Emissions and Emissions Modeling System, were applied to the eastern United States, with emphasis on the northeastern Ozone Transport Region in terms of their response to oxides of nitrogen and volatile organic carbon-focused controls on the estimated design values. With the 8-hr O3 NAAQS set as a bright-line test, it was found that a given area could be termed as being in or out of attainment of the NAAQS depending upon the modeling system. This suggests the need to provide an estimate of model-to-model uncertainty in the relative reduction factor (RRF) for a better understanding of the uncertainty in projecting the status of an area's attainment. Results indicate that the model-to-model differences considered in this study introduce an uncertainty of the future estimated design value of ∼3–5 ppb.

Implications of the new ozone National Ambient Air Quality Standards for compliance in rural areas

The U.S. Environmental Protection Agency (EPA) has recently promulgated new National Ambient Air Quality Standards (NAAQS) for ozone (O3). The new standard is based on an 8‐hour average O3 concentration instead of a 1‐hour average, as was the previous standard. Analysis of O3 concentrations measured at rural sites in the eastern United States in the Aerometric Information Retrieval System (AIRS) network, the Southern Oxidant Study's Spatial Ozone Network (SON), and EPA's Clean Air Status and Trends Network (CASTNet) during 1993–1995 indicates that 30–50% of these sites would have been noncompliant under the new standard, as compared with only 2–12% under the old standard. These results suggest that the new standard will thus require a major shift in emphasis in the nation's pollution control strategy from an urban‐centered focus to a more regional emphasis. This in turn will require the development of a more comprehensive, truly rural air quality monitoring network in coming years.

Measurement of Ozone Levels by Ship Along the Eastern Shore of Lake Michigan

Recent exceedances of the ozone National Ambient Air Quality Standard (NAAQS) in the southern Lake Michigan basin have been the focus of much attention. The Wisconsin Department of Natural Resources, the Illinois Department of Environmental Protection, and the Michigan Department of Natural Resources have conducted studies to quantify the role that intra-regional transport has had on exceedance days. All three studies identified potential mechanisms based on surface and aloft ozone monitoring, but expressed concern over the bias that could be introduced by the lack of meteorological and monitoring data over Lake Michigan. To gain a better understanding of the processes occurring over the Lake, the Michigan Department of Natural Resources and the Grand Rapids Air Pollution Control Division carried out a ship-based monitoring experiment for ozone along the eastern shore of Lake Michigan. The experiment was conducted on the Afternoon of July 29, 1988.

On the non-randomness of high-pollution days

The U.S. Environmental Protection Agency has changed the compliance criterion for the ozone national ambient air quality standard and has suggested a similar criterion in the proposed revision of the CO air quality standards. The criteria have been changed from counting the number of hours of exceedance per year to counting the number of days of exceedance per year. The purpose of this revision was, presumably, to avoid multiple-counting of single, unusual meteorological events. Since meteorological events, unusual or otherwise, often last more than one day, the new compliance criterion again suffers from the pitfall of multiple counting of single events. In this paper, statistical techniques (run tests and autocorrelations) were used to investigate the tendency of high pollution days and high-temperature days to occur in aggregates. The pollutants considered are oxidants, CO and NO 2. The data used are from the California South Coast Air Basin and cover the period from 1969 to 1978. Positive associations of high-pollution days are clearly indicated in this analysis. By use of a first order Markov normal process, it was shown that an increase in serial correlation would “flatten” the distribution of P(m) (the probability of exceeding the air quality standard for m days) and thereby reduce the reliability of the compliance criterion.

An Air Quality Data Analysis System for Interrelating Effects, Standards, and Needed Source Reductions: Part 6. Calculating Concentration Reductions Needed to Achieve the New National Ozone Standard

The new ozone National Ambient Air Quality Standard specifies that the expected number of days per calendar year that the 1 hour average ozone concentration can exceed 0.12 ppm must be equal to or less than 1. This paper describes a method to calculate design frequency, design concentration, and the percentage concentration reduction necessary to achieve this standard. The design frequency is once per year (1/365) if daily maximum hour ozone concentrations are available at a particular site for an equal number of days in summer (April through September) and winter (October through March). An equation is used to adjust design frequency as a function of the number of summer and winter samples available. The design concentration (the ambient concentration measured at the design frequency) needs to be reduced to 0.12 ppm. Graphical and digital methods for determining the design concentration are presented. Percentage concentration reductions needed to achieve the standard are calculated for each site which has ozone concentration data available in the National Aerometric Data Bank for at least half of the days in one summer of years 1975 through 1977. The degree of reduction calculated for the site with the highest concentrations in each county is indicated by shading on a map of the United States.