Session Presentations

Grainger, S.T.        

The UK Government considers air pollution to be a grave threat to human health, and with public controversy, the UK has installed a series of monitoring stations over the country to measure air pollutants. These air pollutants include various Nitrogen Oxides (including Nitrogen Monoxide, Nitrogen Dioxide and Oxides of Nitrogen) and Black Carbon. Two of the most researched monitoring stations nationwide are within the city of Glasgow, namely the High Street and Townhead monitoring stations, which measure air quality at the roadside and in urban ambient air, respectively. While these monitoring stations are well researched, the supply of air pollution within the complex inner-city location has been poorly understood because of the overemphasis on nearby road emissions. However, this work uses the ratio between Nitrogen Monoxide vs Black Carbon and Nitrogen Dioxide vs Black Carbon to understand better the source of air pollution at more distant sources. The ratio of BC to Nitrogen Oxides is taken to be low when either from re-suspended particles or from particularly dirty processes. Alternatively, when the ratio between BC and Nitrogen Oxides is high, sources of nitrogen are taken to be present such as vehicular emissions and industrial sources. When this understanding is combined with advanced statistical analysis, though RStudio's OpenAir package (as developed by Carslaw) together with simple back-trajectory analysis, it is possible to show new and undiscovered sources of air pollution which are overwhelmed by the local phenomenon, but undoubtedly contribute to the total source apportionment of air pollution. In this way, new and undiscovered sources of air pollution were discovered at the High Street monitoring station, which included a local brewery, multi-story car park, and several major road junctions. While the Townhead monitoring station now shows effects from a major bus station, highway intersection and a major source of immediately local air pollution from cook smoke from an adjacent restaurant. Such a technique could readily be used at other monitoring stations internationally to support source apportionment studies.

Rebecca Matichuk,¹ Christian Hogrefe,² Gail Tonnesen,¹ Rob Gilliam,² Sergey Napelenok,² Bill Hutzell,² Daiwen Kang,² Jesse Bash,² Rohit Mathur,² George Pouliot,² Wyat Appel,² Gordon Pierce,³ Kevin Briggs,³ Kira Shonkwiler³

¹EPA, Region 8, Office of Air and Radiation, Air Toxics, Radiation, & Modeling Branch

²EPA, Office of Research & Development, Center for Environmental Measurement and Modeling

³Colorado Department of Public Health and Environment

The Denver Metro/North Front Range (DMNFR) ozone nonattainment area (NAA) in Colorado has had unhealthy levels of ozone for the past decade. State and national air quality programs have focused on reducing the emissions of volatile organic compounds (VOCs) and nitrous oxides (NOx), both of which are precursors to ozone formation, to address the elevated ozone in this area. It is speculated that the effects of these emission reductions may be partially offset by increasing levels of background ozone and increases in local emissions from population growth and extensive oil and gas development in the area. Background ozone includes contributions from wildfires, biogenic emissions, lightning NOx emissions, international anthropogenic pollution, and stratospheric intrusions.

A collaborative effort among EPA Region 8, the Office of Research and Development (ORD), the Office of Air Quality Planning and Standards (OAQPS) and the Colorado Department of Public Health and Environment (CDPHE) have developed a hemispheric-to-regional scale air quality model platform to simulate the transport and chemistry of ozone in the DMNFR NAA in Colorado and to estimate source contributions to simulated ozone. The platform uses the Weather Research and Forecasting (WRF) model and EPA's 2014 National Emissions Inventory (NEI) and the latest Community Multiscale Air Quality (CMAQ) model that includes the Integrated Source Apportionment Method (ISAM). This study focuses on July and August 2014 to align with two Colorado field studies that provided an extensive set of measurement data to evaluate the air quality model platform. This study assesses model performance through a comprehensive evaluation and detailed comparisons with measurements of meteorological variables, ozone, and ozone precursor species from a variety of surface, airborne and mobile platforms. Initial results show that the CMAQ model is biased low for ozone and its precursors during high ozone episodes. ISAM results for both the regional and hemispheric scale simulations are analyzed to quantify the contributions of various anthropogenic and natural emission sources to simulated ozone in the DMNFR, particularly during high ozone episodes.

Shupeng Zhu¹, Andre Paradise², Michael Mac Kinnon¹, Donald Dabdub², G. S. Samuelsen¹

¹Advanced Power and Energy Program, University of California, Irvine, CA 92697, USA

²Computational Environmental Sciences Laboratory, University of California, Irvine, CA 92697, USA

The Clean Air Act requires the United States Environmental Protection Agency (EPA) to review routinely the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (PM_2.5). The current NAAQS, set in 2012, mandates that levels of PM_2.5 do not exceed an annual average of 12 g/m³ and a 24-hour average of 35 g/m³. However, the Independent Particulate Matter Review Panel recently concluded that the current PM_2.5 standard does not protect public health adequately. Instead, the standard should be replaced with concentrations not exceeding an annual average of 8-10 g/m³ and a 24-hour average of 25-30 g/m³. In this study, the potential health benefits from implementing the proposed air quality (AQ) standard is evaluated for California based on both observational and simulated air quality data. Two baselines are generated: 1) a 2018 case constructed using satellite and ground-based observational data, and 2) a 2035 case based on California Air Resources Board emission projections. Both cases are then fully developed at a 4 km x 4 km resolution using the Community Multiscale Air Quality (CMAQ) model. Also, for both cases, three scenarios are assessed for statewide attainment of 1) the current AQ standard, 2) the lenient AQ standard (10 g/m³ annually and 30 g/m³ daily), and 3) the stringent AQ standard (8 g/m³ annually and 25 g/m³ daily). Finally, the health benefits between each of the attainment scenarios and their corresponding baseline are quantified using the BenMAP model. Research results indicate that significant monetary health benefits are expected for both cases when the air quality standard is updated to any of the proposed versions. Furthermore, results support the conclusions of the Independent Particulate Matter Review Panel which state that a reduction in the PM_2.5 standard would yield socio-economic benefits and protect public health.

Marcus Trail, Chris Emery, Chris Lindhjem, Tejas Shah, Greg Yarwood

During periodic winter stagnation episodes in the Salt Lake basin, fine particulate (PM_2.5) concentrations can exceed the national air quality standard, primarily due to a buildup of ammonium nitrate. This study investigated causes for an ammonia (NH₃) emissions shortfall in the photochemical modeling system employed by the Utah Division of Air Quality (UDAQ) to support the recent Salt Lake City PM_2.5 State Implementation Plan (SIP). We reviewed NH₃ emission inventories and recently measured concentration patterns; investigated modeling uncertainties and deficiencies, updated the UDAQ modeling system and refined modeled NH₃ emissions; and re-evaluated modeling results and PM_2.5 sensitivity to NH₃ and NOx emissions. We achieved major improvement in simulated NH₃ and ammonium nitrate concentrations by scaling up NH₃ emissions from gasoline vehicles by a factor of about 2.5, a modification that is supported by evidence in the literature. We also found that model-measurement comparisons benefited from a reduction in vertical mixing and an increase in snow albedo that enhances photochemical production of nitrate. However, the model was insensitive to the introduction of bi-directional NH₃ surface exchange and other chemical modifications. Our modeling results indicate that with these changes, the inorganic PM_2.5 chemical environment in the basin can spatially and temporally vary between ammonia-limited and nitrate-limited, which is consistent with past field studies. This chemical balance has major implications for accurately projecting future PM_2.5 according to anticipated sector-specific emission inventory changes.

Jeongran Yun, Winston Hao, Eric Zalewsky, Ruby Tian, and Kevin Civerolo

Division of Air Resources, New York State Department of Environmental Conservation

Estimated design values for the future year (DVFs), as calculated from air quality modeling results, are used for a model attainment demonstration for the ozone National Ambient Air Quality Standards (NAAQS). The DVF for ozone is calculated by multiplying a baseline 5-year weighted design value by a model-derived Relative Response Factor (YYF). An YYF for a site represents a fractional change in ozone at the site between base and future year air quality modeling results based on emissions changes. EPA's guidance for modeled attainment demonstration recommends calculating an YYF for a site using the 3x3 method that uses a 3x3 grid cell array surrounding the monitoring site. Ozone model performance in coastal areas is often poor due to the land/water interface in the air quality and meteorological models. Therefore, the YYF/DVF may not be reliable when including water cells (more than 50 percent of the grid cell area is water) for those monitoring sites located in coastal areas like the New York City metropolitan area. The guidance allows for consideration of a modified 3x3 method (considering a removal of the unrepresentative cells) for those monitoring sites that may be affected by a specific local topographic or geographical feature such as a water body. In this study, four different YYF/DVF calculation methods will be evaluated for those monitoring sites in coastal areas. The first method is the EPA's recommended 3x3 method. The second method is a modified 3x3 method that uses a 3x3 grid cell array eliminating the grid cells that are classified as water cells and that do not contain the monitoring site. This method includes a water cell in the YYF calculation if the monitoring site is located in water cell. The third method is a further modified 3x3 method that excludes all water cells including the water cell in which the monitoring site is located. The fourth method is a 1x1 method that uses one grid cell where the monitoring site is located. The Community Multiscale Air Quality (CMAQ) and Comprehensive Air quality Model with eXtensions (CAMx) modeling results will be used for the evaluation using both the 2016/2023 version 1 modeling platform and the 2011/2017/2023 modeling platform.

Xuguo Zhang, Jimmy C. H. Fung*, Alexis K. H. Lau, Md Shakhaoat Hossain, Peter K. K. Louie, and Wei (Wayne) Huang

Ozone (O3) pollution had been worsening in China, posing significant challenges to human health. The Nitrogen Dioxide (NO2) control would trigger the rising of O3 in the response of released control policies. This study, proposing a novel sensitivity analysis methodology, explored the effectiveness of the integrated sectoral air quality control policies from health co-benefits perspective. Air quality improvement and the health co-benefits for the two-pollutant were calculated to obtain an in-depth understanding of the O3 control. The results showed that the integral health co-benefits of the two-pollutant had been improving, although the O3 concentration was deteriorating. The region-based annual averaged NO2 concentration exhibited a larger reduction in Hong Kong (HK) than that in the Pearl River Delta Economic Zone (PRD EZ). The super-regional control scenario presented little impact for NO2, indicating a short lifetime of NO2, affected more by local sources. The 13th Five-year Plan measures brought significant health improvement for Shenzhen and HK. The less strengthened NO2 control regions should learn from the regions with greater NO2 reduction, because of larger health benefits gained. The control policies on power, traffic, industry, and other area sectors demonstrated a considerable health improvement for the major PRD EZ cities and HK. Joint national control efforts could make the domain-wide health risks under the safety line. The increasing power demand of electric vehicles offset the health co-benefits in the power generation sector, calling for strengthened efforts in the traffic sector, particularly for the regions with O3 formation of volatile organic compounds limited regime.