Office of Air Quality Planning and Standards
Office of Air Quality Planning and Standards
Appel K.W.,National Exposure Research Laboratory |
Napelenok S.L.,National Exposure Research Laboratory |
Foley K.M.,National Exposure Research Laboratory |
Pye H.O.T.,National Exposure Research Laboratory |
And 19 more authors.
Geoscientific Model Development | Year: 2017
The Community Multiscale Air Quality (CMAQ) model is a comprehensive multipollutant air quality modeling system developed and maintained by the US Environmental Protection Agency's (EPA) Office of Research and Development (ORD). Recently, version 5.1 of the CMAQ model (v5.1) was released to the public, incorporating a large number of science updates and extended capabilities over the previous release version of the model (v5.0.2). These updates include the following: improvements in the meteorological calculations in both CMAQ and the Weather Research and Forecast (WRF) model used to provide meteorological fields to CMAQ, updates to the gas and aerosol chemistry, revisions to the calculations of clouds and photolysis, and improvements to the dry and wet deposition in the model. Sensitivity simulations isolating several of the major updates to the modeling system show that changes to the meteorological calculations result in enhanced afternoon and early evening mixing in the model, periods when the model historically underestimates mixing. This enhanced mixing results in higher ozone (O3) mixing ratios on average due to reduced NO titration, and lower fine particulate matter (PM2. 5) concentrations due to greater dilution of primary pollutants (e.g., elemental and organic carbon). Updates to the clouds and photolysis calculations greatly improve consistency between the WRF and CMAQ models and result in generally higher O3 mixing ratios, primarily due to reduced cloudiness and attenuation of photolysis in the model. Updates to the aerosol chemistry result in higher secondary organic aerosol (SOA) concentrations in the summer, thereby reducing summertime PM2. 5 bias (PM2. 5 is typically underestimated by CMAQ in the summer), while updates to the gas chemistry result in slightly higher O3 and PM2. 5 on average in January and July. Overall, the seasonal variation in simulated PM2. 5 generally improves in CMAQv5.1 (when considering all model updates), as simulated PM2. 5 concentrations decrease in the winter (when PM2. 5 is generally overestimated by CMAQ) and increase in the summer (when PM2. 5 is generally underestimated by CMAQ). Ozone mixing ratios are higher on average with v5.1 vs. v5.0.2, resulting in higher O3 mean bias, as O3 tends to be overestimated by CMAQ throughout most of the year (especially at locations where the observed O3 is low); however, O3 correlation is largely improved with v5.1. Sensitivity simulations for several hypothetical emission reduction scenarios show that v5.1 tends to be slightly more responsive to reductions in NOx(NO+NO2), VOC and SOx (SO2+SO4) emissions than v5.0.2, representing an improvement as previous studies have shown CMAQ to underestimate the observed reduction in O3 due to large, widespread reductions in observed emissions. © Author(s) 2017.
Johns D.O.,U.S. Environmental Protection Agency |
Stanek L.W.,U.S. Environmental Protection Agency |
Walker K.,Health Effects Institute |
Benromdhane S.,Office of Air Quality Planning and Standards |
And 5 more authors.
Environmental Health Perspectives | Year: 2012
Objectives: The U.S. Environmental Protection Agency is working toward gaining a better understanding of the human health impacts of exposure to complex air pollutant mixtures and the key features that drive the toxicity of these mixtures, which can then be used for future scientific and risk assessments. Data sources: A public workshop was held in Chapel Hill, North Carolina, 22-24 February 2011, to discuss scientific issues and data gaps related to adopting multipollutant science and risk assessment approaches, with a particular focus on the criteria air pollutants. Expert panelists in the fields of epidemiology, toxicology, and atmospheric and exposure sciences led open discussions to encourage workshop participants to think broadly about available and emerging scientific evidence related to multipollutant approaches to evaluating the health effects of air pollution. Synthesis: Although there is clearly a need for novel research and analytical approaches to better characterize the health effects of multipollutant exposures, much progress can be made by using existing scientific information and statistical methods to evaluate the effects of single pollutants in a multipollutant context. This work will have a direct impact on the development of a multipollutant science assessment and a conceptual framework for conducting multipollutant risk assessments. Conclusions: Transitioning to a multipollutant paradigm can be aided through the adoption of a framework for multipollutant science and risk assessment that encompasses well-studied and ubiquitous air pollutants. Successfully advancing methods for conducting these assessments will require collaborative and parallel efforts between the scientific and environmental regulatory and policy communities.
Dolwick P.,Office of Air Quality Planning and Standards |
Audette L.,U.S. Environmental Protection Agency |
Davidson K.,U.S. Environmental Protection Agency |
Lynch J.,U.S. Environmental Protection Agency |
Fox T.,Office of Air Quality Planning and Standards
HARMO 2010 - Proceedings of the 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes | Year: 2010
Previous studies have concluded that emissions from ocean-going marine vessels may cause as many as 60,000 deaths annually worldwide. In this study, emissions of NOx, SOx, and PM from shipping emissions are shown to contribute significantly to poor air quality across North America and are increasingly contributing to the amount of sulfur and nitrogen being deposited in the U.S. and Canada. The outputs from a series of regional air quality simulations, using the Community Multiscale Air Quality (CMAQ) modeling system, were paired with several ecosystem models to look at the impacts of potential regulations on ocean-going vessels on human health and welfare. As part of this analysis, several innovative linkages were developed to relate projected changes in air quality to impacts on health and welfare metrics such as human mortality, acidification of aquatic and terrestrial ecosystems, and forest health. This paper will summarize the results of these integrated modeling systems and demonstrate that reductions in ship emissions would produce widespread benefits that outweigh the costs of any potential controls. Additionally, several sensitivity tests were conducted to quantify the air quality and health impacts of ship emissions at various distances from the North American shoreline. Based on this modeling, a joint proposal from the United States, Canada, and France to amend MARPOL Annex VI to designate specific areas of North American coastal waters as an Emission Control Area (ECA) was accepted by the International Maritime Organization (IMO) in March 2010. This ECA is scheduled to begin to reduce emissions as early as July 2010 and is expected to deliver substantial public health benefits to many people living in the U.S., Canada and French territories, as well as to marine and terrestrial ecosystems over the next decade.