An Integrated Assessment Model for Fine Particulate Matter in Europe

Exposure to fine particles in the ambient air is recognized as a significant threat to human health. Two pathways contribute to the particle burden in the atmosphere: Fine particles originate from primary emissions, and secondary organic and inorganic particles are formed from the gas phase from the emissions of 'conventional' pollutants such as SO₂, NO_x, VOC and NH₃. Both types of particulate matter can be transported over long distances in the atmosphere. An integrated assessment model for particulate matter developed at IIASA addresses the relative importance of the different types of particulates, distinguishing primary and secondary particles and two size fractions. The model projects these emissions into the future and seeks cost-effective strategies for reducing health risks to population. The model integrates the control of primary emissions of fine particles with strategies to reduce the precursor emissions for the secondary aerosols. Preliminary results addressing the PM_2.5 fraction of both primary and secondary particulate matter indicate that in Europe the exposure to particulates will be significantly reduced as a side effect of the emission controls for conventional air pollutants (SO₂, NO_x, NH₃).     

An Assessment of the Mobile Source Contribution to PM10 and PM2.5 in the United States

Mobile sources are significant contributors to ambient particulate matter (PM) in the United States. As the emphasis shifts from PM₁₀ to PM_2.5, it becomes particularly important to account for the mobile source contribution to observed particulate levels since these sources may be the major contributor to the fine particle fraction. This is due to the fact that most mobile source mass emissions have an aerodynamic diameter less than 2.5 µm, while the particles of geological origin that tend to dominate the PM₁₀ fraction generally have an aerodynamic diameter greater than 2.5 µm. A common approach to assess the relative contributions of sources to observed particulate mass concentrations is the application of source apportionment methods. These methods include material balance, chemical mass balance (CMB), and multivariate receptor models. This paper describes a number recent source attribution studies performed in the United States in order to evaluate the range of the mobile source contribution to observed PM. In addition, a review of the methods used to apportion source contributions to ambient particulate loadings is presented.     

Atmospheric Emission Inventory for Natural and Anthropogenic Sources and Spatial Emission Mapping for the Greater Athens Area

A spatially, temporally and chemically resolved emission inventory for particulate matter and gaseous species from anthropogenic and natural sources was created for the Greater Athens Area (GAA; base year, 2007). Anthropogenic sources considered in this study include combustion (industrial, non-industrial, commercial and residential), industrial production, transportation, agriculture, waste treatment and solvent use. The annual gaseous pollutants (????x, SOx, non-methane volatile organic compounds (NMVOCs), CO and ????₃) and particulate matter (PM_2.5 and PM_2.5?C10) emissions were derived from the UNECE/EMEP database for most source sectors (SNAP 1?C9; 50?×?50 km²) and their spatial resolution was increased using surrogate spatial datasets (land cover, population density, location and emissions of large point sources, emission weighting factors for the GAA; 1?×?1 km²). The emissions were then temporally disaggregated in order to provide hourly emissions for atmospheric pollution modelling using monthly, daily and hourly disintegration coefficients, and additionally the chemical speciation of size-segregated particles and NMVOCs emissions was performed. Emissions from agriculture (SNAP 10) and natural emissions of particulate matter from the soil (by wind erosion) and the sea surface and of biogenic gaseous pollutants from vegetation were also estimated. During 2007 the anthropogenic emissions of CO, SOx, NOx, NMVOCs, NH₃, PM_2.5 and PM_2.5?C10 from the GAA were 151,150, 57,086, 68,008, 38,270, 2,219, 9,026 and 3,896 Mg, respectively. It was found that road transport was the major source for CO (73.3%), NMVOCs (31.6%) and NOx (35.3%) emissions in the area. Another important source for NOx emissions was other mobile sources and machinery (23.1%). Combustion for energy production and transformation industries was the major source for SOx (38.5%), industrial combustion for anthropogenic PM_2.5?C10 emissions (59.5%), whereas non-industrial combustion was the major source of PM_2.5 emissions (49.6%). Agriculture was the primary NH₃ source in the area (72.1%). Natural vegetation was found to be an important source of VOCs in the area which accounted for approximately the 5% of total VOCs emitted from GAA on a typical winter day. The contribution of sea-salt particles to the emissions of PM_2.5 was rather small, whereas the emissions of resuspended dust particles exceeded by far the emissions of PM_2.5 and PM_2.5?C10 from all anthropogenic sources.     

Projections of SO2, NOx,NH3 and VOC Emissions in East Asia Up to 2030

Starting from an inventory of SO₂, NO_x, VOC and NH₃ emissions for the years 1990 and 1995 in East Asia (Japan, South and North Korea, China, Mongolia and Taiwan), the temporal development of the emissions of the four air pollutants is projected to the year 2030 based on scenarios of economic development. The projections are prepared at a regional level (prefectures or provinces of individual countries) and distinguish more than 100 source categories for each region. The emission estimates are presented with a spatial resolution of 1×1 degree longitude/latitude. First results suggest that, due to the emission control legislation taken in the region, SO₂ emissions would only grow by about 46 percent until 2030. Emissions of NO_x and VOC may increase by 95 and 65 percent, respectively, mainly driven by the expected increase in road traffic volume. Ammonia, mainly emitted from agriculture, is projected to double by 2030.     

Development of a Multi-Resolution Emission Inventory and Its Impact on Sulfur Distribution for Northeast Asia

Emissions in East Asia for 1993 by administrative units and source types are estimated to support regional emission assessments and transport modeling studies. Total emission of SO_x, NO_x, soil NO_x, N₂O, and NH₃ are 24 150, 12 610, 1963, 908, and 8263 kton yr^-1, respectively.China's emission contribution is the highest for every species.The area sources are the most significant source type for SO_x and NO_x, but the fraction due to mobile source is highest for NO_x. Major LPSs are located from the middle to the east part of China, south and middle-west part of South Korea, and the east part of Japan. The area sources of SO_x show a pattern similar to population density, whereas NH₃ shows a strong landuse dependency. Detail emissions analysis reveals higher SO_x emission `cores' within each province. The estimated emissions are used to estimate sulfur deposition in the regions. The seasonal average sulfur distribution amounts are estimated from the ATMOS2 chemical transport model. The results showed anti-correlation with temperature for sulfur (SO₂ + SO₄ ^-2) concentrations and a positive correlation with rainfall for deposition.     

Bench Scale Evaluation of a Chemo-biochemical Process for Desulphurization of Gaseous Streams Containing Hydrogen Sulphide

Gases and suspended particulate matter are sampled and measured in situ at different sites within the city of Madrid to determinethe air pollution in the city. Lead concentrations in air are also determined. The information needed to assess levels of contaminants is obtained combining several analytical techniques,which provide real time concentration data of particles andgases. Particulate matter (PM), SO₂, CO, O₃, NO_x,NO₂, CH₄, total hydrocarbons and Pb were measured. Concentrations of pollutants are averaged over periods of hours,days, months and years. Variations of contaminant concentrationsin the last years are presented. Spatial and temporal distribution follows that of the traffic, the main source of pollution in Madrid City. Some specific measurements were carriedout to understand the influence of traffic emissions at themeasured site. Further, all measured concentrations never exceeded the European Union Directives.     

Emission Inventories,Emission Control Options and Control Strategies: An Overview of Recent Developments

Accurate emission inventories are crucial for informed decisions about emission control strategies. Emission inventory activities are now well established throughout the world and a large body of resources is available to assist in estimating emissions at the global, regional and local scale. Work is ongoing to refine methodologies and to address additional sources and pollutants such as fine particulate matter. During the last decade innovative concepts for emission control legislation were developed. Market based instruments can achieve envisaged emission reductions at lower costs than conventional approaches. Air quality management is now understood as a multi-pollutant, multi-effect task, which offers a significant cost saving potential if synergistic effects are fully utilized. Integrated assessment models proved useful in managing the vast volume of relevant information needed for the design of cost-effective emission control strategies. Europe and North America have embarked on ambitious control strategies that will lead to significant reductions in the emissions of some of the conventional pollutants (e.g., SO₂, NO_x, VOC). There are also first indications of a structural break that could reverse the long-term growth trend of SO₂ emissions also in the fast developing nations of Asia.     

Gaseous Emissions During the Coal Mining Activity and Neutralizing Capacity of Ammonium

This paper presents the simultaneous measurement of atmospheric concentration of gaseous NH₃, SO₂ and NO₂, and particulate NH ₄ ⁺ released from the mining activities of coal-mine area, Tirap colliery, Margherita (Assam). Gas samples were collected by impinger method and were analyzed colorimetrically. The vapor-phase concentration of NH₃, SO₂, and NO₂ range between 4.7?C40.03, 1.47?C6.14, and 1.92?C2.40???g/m³. The NH ₄ ⁺ concentration in PM₁₀ and PM_2.5 ranges between 0.02?C0.07 and 0.008?C0.03???g/m³, respectively. Moderately high concentrations of NH₃ and SO₂ on the first day were due to the coal-burning activity near the sampling site, while the low concentration of NO₂ is due to less vehicle density near the sampling point. All the observed concentrations are below than those reported for the urban areas and the prescribed limit fixed by National Ambient Air Quality Standard, India. Study indicates that ammonia is the major neutralizing agent for sulfate and nitrate ions present in the particulate matter during mining activities.     

Towards a Science-Based Integrated Ozone-Fine Particle Control Strategy

Epidemiology studies relating health effects to ambient levels of ozone and fine particles have led to the modification of standards in the United States for these pollutants (substitution of an 8-h standard for ozone at 80 ppbv, and addition of 24-h and annual standards for fine particles). The interrelationships of these pollutants in the atmosphere suggest the need for an integrated, science-based strategy for their control. Secondary ozone formation has been controlled through emission controls on VOC and NO_x precursors. Fine particles are secondary products largely resulting from the oxidation of precursors (SO₂, NO_x, and VOCs). The key intermediates in both types of secondary process are free radical species and the photochemically labile compounds that produce them in the atmosphere. However, due to the complex and nonlinear nature of the processes, reductions in precursors may lead to unexpected changes in ozone and fine particle formation rates. For example, reduction in NO_x emissions may reduce ozone and nitric acid levels, but lead also to increased rates of sulfate formation in clouds and increased ammonia availability for neutralization of acidic sulfate aerosols. Reductions of SO₂ may reduce aerosol sulfate levels in the summer, but have no effect in other seasons. Reductions in VOCs may reduce ozone levels in urban core areas, but not elsewhere. An integrated, regionally and seasonally specific, emission reduction strategy is needed to cost-effectively reduce both ozone and fine particle levels.     

Source Apportionment of the Atmospheric Aerosol in Lahore, Pakistan

Samples of airborne particulate matter (PM_2.5) were collected at a site in Lahore, Pakistan from November 2005 to January 2006. A total of 129 samples were collected using an Andersen Reference Ambient Air Sampler 2.5-400 sampler and analyzed for major ions, trace metals, and organic and elemental carbon concentrations. The data set was then analyzed by positive matrix factorization (PMF) to identify the possible sources of the atmospheric PM collected in this urban area. Six factors reproduced the PM_2.5 sample compositions with meaningful physical interpretation of the resolved factors. The sources included secondary PM, diesel emissions, biomass burning, coal combustion, two-stroke vehicle exhaust, and industrial sources. Diesel and two-stroke vehicles contributed about 36%, biomass burning about 15%, and coal combustion sources around 13% of the PM_2.5 mass. Nearly two thirds of the PM_2.5 mass is carbonaceous material. Secondary particles contributed about 30% of PM_2.5 mass. The conditional probability function (CPF) was then used to help identify likely locations of the sources present in this area. CPF analysis point to the east and northeast, which are directions of urban and industrial areas located across the border near Amritsar, India as the most probable source for high PM_2.5 concentration from diesel and two-stroke vehicles exhaust in Lahore. Analysis of those days within three different ranges of PM_2.5 concentration shows that most of the measured high PM_2.5 mass concentrations were driven by diesel and two-stroke vehicle emissions including the associated primary sulfate. The use of the potential source contribution function (PSCF) to find the source locations of regionally transported particles is inapplicable in situations when high PM_2.5 concentrations are dominated by local sources and local meteorology.     

Visibility Variation with Air Qualities in the Metropolitan Area in Southern Taiwan

Principal component analysis (PCA) was used to analyze variationsin visibility compared with (1) variations in meteorological variables in the period 1961 to 1998, and (2) criteria air pollutant (SO₂, CO, O₃, NO_x and PM₁₀) concentrations monitored between 1994 and 1998, in the Kaohsiungmetropolitan area. Whilst average visibility during the 1960'sexceeded 20km, it had deteriorated to 5–10 km in theperiod 1994 to 1998. PCA identified seven components witheigenvalues greater than one. The principal componentsidentified accounted for variability related to PM₁₀concentration, ozone-related pollutants, oil combustion,and traffic emissions. Furthermore, spatial and temporalvariations in PM₁₀ were consistent throughout thecity. Variation in SO₂ levels followed a similarpattern at Tsoying, Shanming, Chiankin and Chiancheng.Industrial pollution and traffic emissions, SO₂, COand NO_x, from the Hsiaokang area remained within thearea. However, similar patterns of SO₂ andNO_xat Fengshan and Jenwu indicate that industrial emissionsfrom the latter were probably transported to the former.Much of the first principal component is based onPM₁₀ variability, suggesting that, of the fivecriteria pollutants studied, PM₁₀ is the majorcontributor to visibility deterioration. It is known thatPM_2.5 concentration is more closely associated withvisibility changes than is PM₁₀. However, becausePM₁₀ and PM_2.5 are strongly associated inKaohsiung, a targeting reduction in PM₁₀ may imply areduction in visibility.     

废气再循技术对正丁醇/柴油燃烧颗粒结构及分形特征的影响

为深入了解添加含氧燃料和废气再循环技术(exhaust gas recirculation,EGR)共同作用对颗粒结构及分形特征的影响,运用颗粒分级采样装置采集了EGR率分别为0、10%、20%时,柴油机燃用正丁醇质量百分比为10%的正丁醇/柴油混合燃料(N10)的燃烧颗粒(N10EGR0、N10EGR10%、N10EGR20%),通过电镜试验和图像处理技术,开展了不同EGR率对正丁醇/柴油燃烧颗粒的影响研究,分析了颗粒群的微观结构、平均粒径、分形维数,基本碳粒子的层面间距、微晶尺寸等物理结构参数的变化规律,结果表明,N10EGR0、N10EGR10%、N10EGR20%燃烧颗粒群整体呈现团簇状结构,颗粒粒径范围主要集中在30~70 nm之间,呈正态单峰分布;随着EGR率的增加,粒径范围向大粒径方向移动,平均粒径逐渐增大,N10EGR20%与N10EGR0相比,平均粒径增大约为19%;计盒维数逐渐减小,表明颗粒间的团簇程度逐渐减弱。不同EGR条件下的基本碳粒子结构相似,呈指纹状球形碳层结构,随EGR率的增加,基本碳粒子的内核碳层排列无序性和外壳石墨晶体结构无规则性增强,平均层面间距和弯曲度逐渐增大,微晶尺寸逐渐减小。该研究为含氧燃料与EGR共同作用对颗粒的形成机理以及降低柴油机颗粒排放的措施提供理论参考。     

Diurnal Characteristics of Suspended Particulate Matter and PM<Subscript>2.5</Subscript> in the Urban and Suburban Atmosphere of the Kanto Plain,Japan

Suspended particulate matter (SPM) and PM_2.5 in the urban and suburban atmosphere of the Kanto Plain of Japan, which includes the Tokyo metropolitan area, during the period 22–26 July 2002 were characterized. Samples of SPM and PM_2.5 were collected by low-volume samplers at 6-h intervals at Suginami, Saitama, and Kisai. At all the sites, the major components of SPM and PM_2.5 were organic carbon (OC), elemental carbon (EC), and sulfate. The ion balance, the size distributions of the ionic species, and the high correlation between SO₄ ^2? and NH₄ ⁺ indicated that the main chemical form of sulfate was (NH₄)₂SO₄. The OC/EC ratios were larger in the daytime than in the nighttime. The correlation coefficients of OC, OC/EC, and SO₄ ^2? with ozone concentrations at inland sites (Saitama, Kisai) were higher than those at the coastal site (Suginami). Bound water and hydrogen and oxygen atoms associated with OC, the amounts of which were estimated with a mass closure model, contributed substantially to the total particle mass. The chemical characteristics of the particles indicated that two mechanisms led to high concentrations of SPM and PM_2.5: (i) an active photochemical process produced high concentrations of OC and sulfate, leading to a high concentration of (NH₄)₂SO₄ in the particles and to production of secondary organic aerosols; (ii) stable meteorological conditions resulted in accumulation of primary particles, mainly emitted from vehicle exhaust, resulting in high concentrations of OC and EC.     

Acid deposition: Perspectives in time and space

Most acid-deposition investigations have been concerned with the impact of nitrogen oxides (NO_x) and sulfur dioxide (SO₂) emissions on Europe and North America. This paper examines three issues beyond this central focus. Major conclusions are 1) ammonia (NH₃) emissions and subsequent nitrogen (N) accumulation in terrestrial ecosystems have the potential to generate significant acidification in terrestrial and aquatic ecosystems; 2) sulfur (S) and N accumulation in environmental reservoirs will not only result in significant and extensive acidification but will also impact the earth's radiation balance, tropospheric oxidizing capacity, ecosystem nutrient balance and groundwater quality; and 3) future emissions will substantially increase in the developing world, especially in Asia. By 2020, Asian emissions of SO₂, NO_x and NH₃ will be equal to or greater than the combined emissions from Europe and North America.     

A Computational Approach Based on GIS Technology for the Development of an Anthropogenic Emission Inventory of Gaseous Pollutants in Greece

This paper describes a computational system developed for the compilation of an anthropogenic emission inventory of gaseous pollutants for Greece. The inventory was developed using a geographical information system integrated with SQL programming language to provide high temporal gridded emission fields for CO, NO₂, NO, SO₂, NH₃ and 23 non-methane volatile organic compounds (NMVOCs) species for the reference year 2003. Activity and statistical data from national sources were used for the quantification of emissions from the road transport, the other mobile sources and machinery sectors and from range activities using top-down or bottom-up methodologies. Annual emission data from existing national and European emission databases were also used. The emission data were spatially and temporally disaggregated using source-specific spatiotemporal indicators. On national scale, the road transport sector produces about 60% of the annual CO and NMVOC total emissions, with gasoline vehicles being the main CO and NMVOC emissions source. The road transport is responsible for approximately half of the higher alkanes and for more than half of the ethene and toluene emissions. The maritime sector accounts for about 40% of the annual total NO_x emissions, most of which are emitted by the international shipping subsector, whilst SO₂ is emitted mainly by the energy sector. The evaluation of the emissions inventory suggests that it provides a good representation of the amounts of gaseous pollutants emitted on national scale and a good characterisation of the relative composition of CO and NO_x emission in the large urban centres.     

The role of nitrogen oxides in oxidant production as predicted by the Regional Acid Deposition Model (RADM)

Regional oxidant distributions produced under various atmospheric conditions and emission scenarios are investigated using the Regional Acid Deposition Model (RADM). RADM is a complex, evolving three-dimensional Eulerian model that describes the chemistry, transport and deposition of tropospheric trace species including SO₂, sulfate, NO _x and volatile organic compounds as well as O₃, other major oxidants and acids. The model calculates the short-term temporal evolution of atmospheric trace gas concentrations and their deposition on the regional scale. This study is focused on oxidant production in the eastern United States and southeastern Canada. The influence of atmospheric conditions is explored by comparing three characteristic winter, summer and spring/fall cases. Base-case 1985 emissions of SO _x , NO _x , volatile organic compounds (VOCs), NH₃ and CO are specified using the comprehensive pollutant emissions inventory developed as part of the National Acid Precipitation Assessment Program (NAPAP). The perturbed case, which represents projected anthropogenic emission changes for 2010, indicates changes in daily total 80 km grid average NO _x emissions ranging from increases of 75% to decreases of 45% and VOC emission changes ranging from increases of 65% to decreases of 20%. The largest NO _x emission changes occur in the northeast, and the largest VOC changes occur in the Gulf Coast area. Ground level grid average midday O₃ concentrations for the 1985 emission cases are highest (on the order of 70 to 100 ppb) in the New York City and Houston metropolitan areas for the summer and spring cases; the summer case also indicates relatively high grid average O₃ concentrations of greater than 80 ppb in the southeast. Winter case values are much lower than summer O₃ values throughout the region, with highs of 40 to 50 ppb occurring in the southeast and the Great Lakes area. Changes in NO _x and other emissions under the complex 2010 emissions scenario for the summer case result in maximum O₃ concentration reductions of 10% in the Houston area and increases in O₃ of a few percent in some rural areas of the southeast. This study underscores the need for more comprehensive assessment of the complex relationships among regional emission changes, oxidant production and atmospheric conditions.     

Summertime study of acid deposition in the Detroit area

A comprehensive acid-deposition measuring station has been set up at the General Motors Technical Center site in Warren, Michigan. A second station is also being operated at a rural site near Lapeer, Michigan, which is approximately 54 km north of the Warren site. This report presents the results of this study for the June-September 1981 period. The rain composition was similar at both sites with the pH averaging 4.1 and the SO₄ ⁼/NO₃ ^? equivalence ratio averaging 2.1:1. This similarity suggests that local sources, i.e., relatively high emissions near the Warren site, and low emissions near the Lapeer site, have little effect on rain composition. The SO₄ ⁼/NO₃ ^? ratio for individual rain events in Warren reflected the SO₂/NO_x emission ratio in the area from which the event had come. Thus, the highest SO₄ ⁼/NO₃ ^? ratios were observed for rains that arrived from the southeast and the lowest ratios for rains from the southwest. No rain events arrived from a northwesterly direction during this sampling period. Measurements were carried out at both sites to estimate the relative contribution of dry deposition. The ambient particulate was acidic about half the time and basic half the time. The acidity in the particulate was due to acid SO₄ ⁼ and the basicity was due to soil-related materials. Gaseous HNO₃ averaged 2.0 μg m^?3while the basic gas, NH₃, averaged 0.83 μg m^?3. Based on these measurements, it was estimated that dry deposition of particles and HNO₃ contributed less than 10% of the total deposition of acidity during this study period.     

Morphology and Solutes Content of Atmospheric Particles in an Urban and a Natural Area of São Paulo State, Brazil

The objectives of this work were to characterize and compare the chemical composition of the water-soluble fraction of the PM₁₀ particles (Dp < 10μm) in two sites: one inside the Metropolitan Area of São Paulo (MASP) and another, 250km apart, inside the State Park of Serra do Mar (CUNHA) part of the Atlantic Forest Reserve, both located in São Paulo State, Brazil. The atmospheric particles were collected during dry and wet season. The morphologic parameters of the particles were characterized for the different size fractions of the collected material. In the aqueous extract of the particulate fine fraction the major ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^?, NO₃ ^?, NH₄ ⁺, SO₄ ^2?) and trace elements (Al, Mn, Fe, Pb, Cd, Zn, Ti, Ni, Cu, Co, Ba) were determined. The morphological characteristics of the particles collected within the MASP are typical of polluted environment while in CUNHA there is no evidence of this type of contribution. Regarding the solute concentrations it was observed that the most abundant major ions and trace elements were K⁺, Ca²⁺, Na⁺, Cl^? and Pb, for CUNHA and NO₃ ^?, SO₄ ^2?, NH₄ ⁺ and Mn, Ni, Pb, Co, Cd and Ba for MASP. These differences are associated with the different sources of the particles. In the urban area they are predominantly of pollution origin, mainly from vehicle emissions, and road dust suspension, while in the State Park they are mainly of biogenic, terrigenous and oceanic origins. For these reasons the CUNHA region can be considered to be a regional reference site for studies concerning eventual disturbances in the Cunha background site, derived from transported pollution.     

Nitrogen oxides,regional transport,and ozone air quality: Results of a regional-scale model for the midwestern United States

An overview of the role of NO _x in the formation of rural O₃, regional transport and its potential impact on urban air quality is presented. An analysis of a specific O₃ excursion in southeast Michigan (8-2-90) is performed based on a combined urban and regional-scale model. The regional component of the model represents transport and photochemistry from sources as far away as Texas. Results suggest that rural O₃ and regional transport sensitive to NO _x emissions and relatively insensitive to changes in volatile organic carbon (VOC) emissions. This differs from the situation in urban areas, where O₃ is sensitive to both NO _x and VOC. Regional transport and upwind NO _x emissions have a significant impact on peak O₃ in Detroit. Implications for urban and regional-scale abatement strategies are discussed.     

Efficacy of nitrogen oxides and hydrocarbons emissions controls in ozone attainment strategies as predicted by the Urban Airshed Model

The primary object of this paper is to provide a preliminary assessment of the effectiveness of NO _x vs Volatile Organic Compounds (VOC) emissions control options in improving O₃ air quality over the New York metropolitan area. To this end, we have applied the Urban Airshed Model (UAM) with the Carbon Bond IV (CB-IV) chemical mechanism utilizing the results of the Regional Oxidant Model (ROM) for the specification of initial/boundary concentrations and wind fields to the UAM. After examining the sensitivity of the predicted O₃ concentrations to initial/boundary conditions and biogenic emissions, we have evaluated the impact of various hypothetical emissions reduction options on O₃ air quality. Nested ROM/UAM simulations with an across-the-board reduction of 75% in the NO _x and VOC emissions from sources located within the New York metropolitan area indicate that the option of VOC-only control is superior to the NO _x -only control in reducing not only peak O₃ levels over the entire modeling domain but also population exposure to unhealthy O₃ levels. The model predicts that the combined 75% NO _x and VOC control option also reduces the peak O₃ concentration, but the improvement in O₃ air quality is less than that predicted for the 75% VOC-only control strategy. Additional modeling analyses with different mix and levels of emissions control and meteorological conditions are needed to confirm these preliminary findings.