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Terrestrial ecosystems help mitigate global warming by sequestering atmospheric carbon dioxide (CO2) through plant photosynthesis, the rate of which is affected by surface ozone (O3) and aerosols under simultaneous impacts of climate change and rising CO2. While the changes in anthropogenic emissions perturb atmospheric components, their consequent impacts on ecosystem productivity in the future climate remain unclear. Here, we apply a fully coupled climate‐chemistry‐vegetation model, ModelE2‐YIBs, to explore the effects of O3 and aerosols from anthropogenic emissions on global gross primary productivity (GPP) under different emission scenarios at 2060. At the present day, anthropogenic air pollutants induce a GPP loss of −1.67 Pg[C] (−4%) in boreal summer with the contributions of −2.18 Pg[C] by O3 and +0.52 Pg[C] by aerosols. At 2060, the detrimental effect of air pollutants on GPP is exacerbated to −1.85 Pg[C] under a high emissions scenario but alleviated to −0.59 Pg[C] under a low emission scenario. The mitigated GPP loss in the latter scenario is owing to the effective control of anthropogenic emissions that on average reduces surface O3 concentrations by 8.14 ppbv globally relative to 2010. Although the CO2 fertilization effect is weaker in the low emission scenario, the strong decline in air pollutants brings additional GPP gains compared to the high scenario. Regionally, such GPP amelioration is close to or even overweighs the CO2 fertilization effect in eastern China and United States, suggesting that the deep cut of anthropogenic emissions can effectively promote future ecosystem productivity over the nowadays polluted regions. Plain Language Summary: Terrestrial ecosystems play a crucial role in reducing global warming through plant photosynthesis. However, this process is sensitive to the changes in environmental factors such as climate, CO2, and air pollutants. Here, we use a climate‐chemistry‐vegetation coupled model to project global ecosystem productivity by the 2060, taking into account impacts of surface ozone and aerosols under simultaneous impacts of climate change and rising CO2. We found that air pollutants result in a 4% loss of global plant productivity during the boreal summer mainly due to the detrimental effects of ozone. By the year 2060, this negative effect could worsen under a high emission scenario but improve under a low emission scenario. The better outcome in the low emission scenario is largely due to a significant reduction in ozone levels, which results from effective control of human‐caused emissions. Regionally, the pollution‐induced improvement in plant productivity shows the highest gains in eastern China and the United States. It suggests that the deep cut of human emissions helps increase ecosystem carbon uptake in the top two carbon emitter countries even with weakened CO2 fertilization effects under the carbon neutrality. Key Points: Anthropogenic ozone and aerosols reduce summertime GPP by 4% at present dayThis GPP loss can be significantly decreased with the deep cut of anthropogenic emissionsThe GPP recovery by air pollution control is comparable to CO2 fertilization in China and United States [ABSTRACT FROM AUTHOR]

The US Environmental Protection Agency (EPA) uses a dynamic approach to enforcing air pollution regulations, with repeat offenders subject to high fines and designation as high priority violators (HPV). We estimate the value of dynamic enforcement by developing and estimating a dynamic model of a plant and regulator, where plants decide when to invest in pollution abatement technologies. We use a fixed grid approach to estimate random coefficient specifications. Investment, fines, and HPV designation are costly to most plants. Eliminating dynamic enforcement would raise pollution damages by 164 percent with constant fines or raise fines by 519 percent with constant pollution damages. (JEL Q52, Q53, Q58) [ABSTRACT FROM AUTHOR]

Dry deposition (DD) is a major loss process for tropospheric ozone and some reactive nitrogen and carbon precursors. We investigate the response of summertime ozone and its production chemistry over the Southeast United States (USA) to variability in this sink. Turning off DD of oxidized nitrogen, ozone, or all species over the United States in the Geophysical Fluid Dynamics Laboratory AM3 model increases regional mean surface ozone by 5, 18, or 25 ppb, respectively. Additional sensitivity simulations demonstrate that, assuming linearity, surface ozone has a similar sensitivity to ozone DD as to NOx emissions. Trends in ozone production efficiency derived from observed relationships between ozone and precursor oxidation products may not solely reflect precursor emission changes if ozone DD varies (e.g., with meteorology). We conclude that DD variability merits consideration when interpreting observed ozone trends. Quantifying the impact of changes in sinks versus sources will require long‐term DD measurements across the region of interest. Plain Language Summary: Ozone is an air pollutant near Earth's surface and a greenhouse gas higher in the atmosphere. While many studies consider which ozone sources should be controlled to reduce air pollution, we focus here on a poorly understood removal pathway, "dry deposition" (DD), to the Earth's surface. We use a model to quantify how ozone responds to changes in the DD of ozone and related gases (oxidized nitrogen and carbon gases). We find that a 50% decrease in DD changes ozone concentrations in the Southeast United States by at least as much as recent changes in national emissions of nitrogen oxides (which form ozone in the presence of sunlight and reactive carbon gases). Our model suggests that DD variability, potentially driven by changes in meteorology or land use, could affect surface ozone trends. However, we lack the observations that would allow an assessment of how DD changes over space and time. Key Points: A 50% decrease in ozone dry deposition has twice the effect on surface ozone over the Southeast USA as a 25% increase in NOx emissionsTwo different metrics for ozone production efficiency show opposite‐signed responses to shutting off ozone dry depositionBounding the influence of ozone dry deposition on tropospheric composition requires long‐term, regional observations of its variability [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to review the management of air pollution in Mexico and strategies that have been considered to correct the issues, including potential future directions to further improve air quality for Mexico's environment and people.Design/methodology/approach Different serious academic databases were searched for material regarding the issue of air pollution in Mexico, such as Scopus and Social Science Citation Index. Regional concern was an important factor that was considered in this review. Material was considered based on its recency, academic importance and veracity. The studies selected mainly ranged from the mid-1990s to 2018.Findings Air pollution in Mexico has been a primary issue for the country's administration and that of Mexico's North American neighbour, the USA. It has contributed significantly to climate change and has had detrimental effects on both the environment and on the health of Mexican citizens in various ways. While efforts to ameliorate the situation have been relatively strong, it is hoped that ongoing cooperation between Mexico, the USA and Canada will influence the development of stricter emissions standards.Originality/value This paper considers current circumstances and whether enough has been done to mitigate Mexico's significant air pollution problem. It also considers several recommendations made by commentators as to potential future directions to rectify the issues, as no similar review has been made for a developing Country. [ABSTRACT FROM AUTHOR]

Abstract The international green infrastructure literature has examined rails-to-trails and freeway-to-boulevard conversions, but these strategies can be impractical or politically unfeasible. An understudied movement among United States cities has demonstrated a strategy for greening freeways that remain in service: freeway cap parks, or decks with parks built in the air space directly above below-grade freeway sections that can help reintegrate communities, conceal traffic, reduce air pollution, and provide green space. We provide the first assessment of the design, function, and placement of freeway cap parks and assess the emerging sustainability discourse of cap park planning. We examine 18 completed and 9 proposed cap parks in 24 U.S. cities to identify four cap park development models that can be adapted worldwide to green below-grade freeway segments and reconnect communities. Given historic disparities in freeway placement, we examined the distribution of cap parks and found they are located in areas that could help address disparities in park access in freeways corridors. Our detailed case studies stress the struggle within the cap park sustainability discourse to balance economic, environmental, and equity concerns. Dallas' Klyde Warren Park is an economic success story, but illustrates how developers use cap parks to sideline equity concerns. Denver's proposed I-70 cap park illustrates strategies to mitigate environmental justice impacts of freeway expansion projects, but equity concerns remain given continuing impacts of the expanded freeway system. Cap parks should be embraced as a vital component of green infrastructure that reconnects and greens cities divided by freeway construction, but planners should take strong steps to address housing affordability and gentrification concerns for adjacent communities. Highlights • Freeway cap parks are parks built above below grade freeway sections • No previous study has examined cap parks as a freeway mitigation strategy • Analyzed plans and the distribution of completed and proposed cap parks in the U.S. • Cap parks offer a valuable mitigation strategy for reconnecting urban communities • Proposed caps locations could help address disparities in park access [ABSTRACT FROM AUTHOR]

Concentrations of atmospheric trace species in the United States have changed dramatically over the past several decades in response to pollution control strategies, shifts in domestic energy policy and economics, and economic development (and resulting emission changes) elsewhere in the world. Reliable projections of the future atmosphere require models to not only accurately describe current atmospheric concentrations, but to do so by representing chemical, physical and biological processes with conceptual and quantitative fidelity. Only through incorporation of the processes controlling emissions and chemical mechanisms that represent the key transformations among reactive molecules can models reliably project the impacts of future policy, energy and climate scenarios. Efforts to properly identify and implement the fundamental and controlling mechanisms in atmospheric models benefit from intensive observation periods, during which collocated measurements of diverse, speciated chemicals in both the gas and condensed phases are obtained. The Southeast Atmosphere Studies (SAS, including SENEX, SOAS, NOMADSS and SEAC4RS) conducted during the summer of 2013 provided an unprecedented opportunity for the atmospheric modeling community to come together to evaluate, diagnose and improve the representation of fundamental climate and air quality processes in models of varying temporal and spatial scales. This paper is aimed at discussing progress in evaluating, diagnosing and improving air quality and climate modeling using comparisons to SAS observations as a guide to thinking about improvements to mechanisms and parameterizations in models. The effort focused primarily on model representation of fundamental atmospheric processes that are essential to the formation of ozone, secondary organic aerosol (SOA) and other trace species in the troposphere, with the ultimate goal of understanding the radiative impacts of these species in the southeast and elsewhere. Here we address questions surrounding four key themes: gas-phase chemistry, aerosol chemistry, regional climate and chemistry interactions, and natural and anthropogenic emissions. We expect this review to serve as a guidance for future modeling efforts. [ABSTRACT FROM AUTHOR]

Environmental policies in the United States have primarily taken the form of media-specific regulations that emphasize end-of-pipe pollution control. This can lead to the shifting of pollution across environmental media, thereby having the potential to solve one environmental problem by creating a new problem. This study uses data from 228 coal-fired power plants that report to the Toxics Release Inventory to conduct an empirical examination of the extent to which media-specific regulation has caused power plants to shift their toxic air releases to waterways, land, or transfers for offsite recycling facilities. Controlling for plant-level fixed effects, scale of production, and environmental inspections and enforcement under air regulation, this study finds that adopting tougher air pollution regulation that designates counties as being in nonattainment status with the National Ambient Air Quality Standards significantly increased toxic releases to waterways and land. [ABSTRACT FROM AUTHOR]

An important issue of regional air quality management is to allocate air quality management funds to maximize environmental and human health benefits. In this study, we use an innovative approach to tackle this air quality management issue. We develop an innovative resource allocation model that allows identification of air pollutant emission control strategies that maximize mortality avoidances subject to a resource constraint. We first present the development of the resource allocation model and then a case study to show how the model can be used to identify resource allocation strategies that maximize mortality avoidances for top five Metropolitan Statistical Areas (MSAs) (i.e., New York, Los Angeles, Chicago, Dallas-Fort Worth, and Philadelphia) in the continental United States collectively. Given budget constraints in the U.S. Environmental Protection Agency’s (EPA) Clean Air Act assessment, the results of the case study suggest that controls of sulfur dioxide (SO2) and primary carbon (PC) emissions from EPA Regions 2, 3, 5, 6, and 9 would have significant health benefits for the five selected cities collectively. Around 30,800 air pollution–related mortalities could be avoided during the selected 2-week summertime episode for the five cities collectively if the budget could be allocated based on the results of the resource allocation model. Although only five U.S. cities during a 2-week episode are considered in the case study, the resource allocation model can be used by decision-makers to plan air pollution mitigation strategies to achieve the most significant health benefits for other seasons and more cities over a region or the continental U.S.Implications: Effective allocations of air quality management resources are challenging and complicated, and it is desired to have a tool that can help decision-makers better allocate the funds to maximize health benefits of air pollution mitigation. An innovative resource allocation model developed in this study can help decision-makers identify the best resource allocation strategies for multiple cities collectively. The results of a case study suggest that controls of primary carbon and sulfur dioxides emissions would achieve the most significant health benefits for five selected cities collectively. [ABSTRACT FROM AUTHOR]

The article explores the issues related to major environmental statutes in the U.S. Topic discussed include laws defined by the Clean Air Act for violators of federal and state laws and regulations on air pollution control; introduction of the Safe Drinking Water Act; and aim of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to clean up hazardous substances at contaminated sites.

There was an increasing interest in reducing production and emission of air pollutants to improve air quality for animal feeding operations (AFOs) in the U.S. in the 21st century. Research was focused on identification, quantification, characterization, and modeling of air pollutions; effects of emissions; and methodologies and technologies for scientific research and pollution control. Mitigation effects were on pre-excretion, pre-release, pre-emission, and post-emission. More emphasis was given on reducing pollutant emissions than improving indoor air quality. Research and demonstrations were generally continuation and improvement of previous efforts. Most demonstrated technologies were still in a limited scale of application. Future efforts are needed in many fundamental and applied research areas. Advancement in instrumentation, computer technology, and biological sciences and genetic engineering is critical to bring major changes in this area. Development in research and demonstration will depend on the actual political, economic, and environmental situations. [ABSTRACT FROM AUTHOR]

The article suggests a solution for reducing air pollution in the U.S. through the Community Clean Air Tax Credit (CCAT Credit) available to people living in communities that have taken steps to cut air pollution. Topics include role of the CCAT in cutting household electricity consumption and building public awareness for air pollution control, and the role of the Clean Air Act in granting power to the U.S. Environmental Protection Agency (EPA) to establish ambient air quality standards.

Air pollution emissions regulation can affect the location, size, and technology choice of potential biofuel production facilities. Difficulty in obtaining air pollutant emission permits and the cost of air pollution control devices have been cited by some fuel producers as barriers to development. This paper expands on the Geospatial Bioenergy Systems Model (GBSM) to evaluate the effect of air pollution control costs on the availability, cost, and distribution of U.S. biofuel production by subjecting potential facility locations within U.S. Clean Air Act nonattainment areas, which exceed thresholds for healthy air quality, to additional costs. This paper compares three scenarios: one with air quality costs included, one without air quality costs, and one in which conversion facilities were prohibited in Clean Air Act nonattainment areas. While air quality regulation may substantially affect local decisions regarding siting or technology choices, their effect on the system as a whole is small. Most biofuel facilities are expected to be sited near to feedstock supplies, which are seldom in nonattainment areas. The average cost per unit of produced energy is less than 1% higher in the scenarios with air quality compliance costs than in scenarios without such costs. When facility construction is prohibited in nonattainment areas, the costs increase by slightly over 1%, due to increases in the distance feedstock is transported to facilities in attainment areas. [ABSTRACT FROM AUTHOR]

Abstract: Technology forcing is a strategy where a regulator specifies a standard that cannot be met with existing technology, or at least not at an acceptable cost. Using the 1970 U.S. Clean Air Act for controlling automobile emissions as a baseline example, we demonstrate the importance of the regulatory implementation process if regulations are to foster technological change. The 1970 legislation required steep emissions reductions for new 1975 and 1976 automobiles, which presented automakers with major technical and economic challenges. Nevertheless, the U.S. Environmental Protection Agency successfully forced the adoption of two marquee control technologies—the catalytic converter in 1975 and the three-way catalyst in 1981. We focus on three factors critical to the implementation process: agency credibility to enforce standards, competitive pressures to drive industry research and development, and uncertainty about technological development. [Copyright &y& Elsevier]

The article discusses the constitutionality of congestion pricing in controlling air pollution and roadway congestion in urban environments. The author argues that programs that assess fees on drivers for using urban roadways may not be effective in reducing either air pollution or congestion and may be unconstitutional. Topics include a taxation scheme in New York City, several court cases regarding taxation and pricing schemes, and disproportionate economic burdens of congestion pricing.

The economics of alternatives to coal combustion, coupled with concerns about coal's significant role in climate change emissions and air pollution, have put intense downward pressure on coal markets, especially in the United States. As coal power generation in much of the world is declining (China being the largest exception), there is renewed interest in how to sustainably, and effectively, use coal without combusting it. A non-exhaustive review of various possible uses for coal across the chemical and material sectors, is provided. Advanced materials and chemicals derived from coal may offer attractive avenues for further research and development that could lay the groundwork for future manufacturing and processing. However, many current applications suffer from being either uneconomic or producing high levels of emissions across their lifecycle. • The consumption of coal for power generation is decreasing, in the U.S. and globally. • Alternative uses of coal may help support domestic manufacturing and industrial sectors. • New processes using coal inhibited by cost and carbon emissions. • Coal conversion technology still burgeoning and requires further R&D. [ABSTRACT FROM AUTHOR]

To effectively control and prevent air pollution, it is necessary to study the influential factors of air quality. A number of previous studies have explored the relationships between air pollution and related factors. However, the methods currently used either cannot well address the multicollinearity problem or fail to explain the importance of the influential factors. Moreover, most of the existing literature limited their studied area in a city or a small region and studied factors in one aspect. There is a lack of studies that analyze the influential factors from the perspective of a country or take into consideration multiple variables. To fill the research gap, this paper proposes a multivariate analysis in the national scale to investigate the most important factors of air quality. In order to study as much influential factors as possible, 171 features ranging from environmental, demographical, economic, meteorological, and energy, were collected and analyzed. To tackle such a "big data" problem, a non-linear machine learning algorithm namely Extreme Gradient Boosting (XGBoost) is utilized to model the relationship and measure the variable importance. Geographical Information System (GIS) is employed to preprocess the diversified variables and visualize the results. Performance of XGBoost is compared with other models and its parameters are tuned using Bayesian Optimization. Experimental results of a case study in the U.S. show that our methodology framework can effectively uncover the important factors of air quality. Six kinds of factors are found to have the largest impact on air quality. Practical suggestions are also proposed from the six aspects to control and prevent air pollution. • This study analyzed the impact factors on AQI of different counties in the U.S. • 171 variables were considered to study the most influential ones. • XGBoost outperforms other commonly seen algorithms in modeling. • Six kinds of factors are found to be most influential on AQI on a national scale. [ABSTRACT FROM AUTHOR]

Research and development has been a key part of the foundation for improvements in US air quality since the establishment of the Environmental Protection Agency (EPA) 50 years ago. Although the scientific accomplishments and advances over the course of EPA's history are often overshadowed by policy debates, much of the air pollution science and engineering we now consider to be routine did not exist when EPA was established. Many of the advances in air pollutant measurement, monitoring, modeling, and control were developed by EPA researchers or supported by EPA programs. The technical foundation built during EPA's early years has since given the Agency the scientific ability to respond quickly and effectively to unexpected and emerging issues. Equally important, EPA also developed approaches to conducting and presenting science in policy settings to ensure that the science was as objective and complete as possible and was communicated effectively. A look back at some of the accomplishments of EPA scientists and engineers provides a reminder that the cumulative effect of continual, incremental advances can result in large and lasting benefits to society.