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MODELING ASSESSMENT OF THE IMPACT OF NITROGEN OXIDES EMISSION REDUCTIONS ON OZONE AIR QUALITY IN THE EASTERN UNITED STATES: OFFSETTING INCREASES IN ENERGY USE
Citation:
PORTER, S., E. GEGO, A. GILLILAND, C. HOGREFE, J. M. GODOWITCH, AND S.T. RAO. MODELING ASSESSMENT OF THE IMPACT OF NITROGEN OXIDES EMISSION REDUCTIONS ON OZONE AIR QUALITY IN THE EASTERN UNITED STATES: OFFSETTING INCREASES IN ENERGY USE. In Proceedings, 28th NATO/CCMS International Technical Meeting, Leipzig, GERMANY, May 15 - 19, 2006. Elsevier Science BV, Amsterdam, Netherlands, 177-188, (2007).
Impact/Purpose:
The framework of accountability is based on measuring environmental outcomes using an integrated environmental assessment model - - assessing and documenting relationships between emissions, air quality, atmospheric deposition, and effects to public health and ecosystems. Work in AMD will focus on relating changes in emissions to changes in environmental conditions prospectively, and the retrospective attribution of observable improvements in environmental conditions to specific emission control strategies.
1.Emission reductions observed in ambient air and atmospheric deposition
Since the 1990 Clean Air Act Amendments, a greater number of stationary sources of SO2 and NOx emissions have installed continuous emissions monitoring systems. Improved systems for tracking emissions from mobile sources have also been developed. At this level, an accountability framework provides a bridge between measured emission reductions and changes in the ambient environment. Resources under this initiative would be applied to analyze specific primary and transformed emission products in ambient air and in atmospheric deposition (e.g., nitrogen oxide, particle nitrate) over relevant geographic areas.
2.Predicted air quality and atmospheric deposition improvements
Resources would be applied to enhance the predictive capability to address whether emissions reductions have resulted in the expected improvements in air quality and deposition, for example:
Reduced ozone, PM2.5 concentrations
Reduced deposition of NOx transformations (e.g., wet and dry deposition of nitrate)
Diagnostic species (e.g., peroxides, nitric acid, ammonia) useful for model evaluations and interpreting dynamic changes in the atmosphere associated emissions reductions
In addition to assessing whether the improvements have occurred, this would also entail assessing whether these improvements can be attributed to specific emission control strategies.This team's objective is to research and develop analytical tools that will quantify the effect of regional NOx emission reductions on ambient air quality, thus providing a measure of control stategy accountability.
Description:
The objective of this study is to examine changes in ambient ozone concentrations estimated by a photochemical air quality model in response to the NOx emission reductions imposed on the utility sector. To accomplish this task, CMAQ air quality model simulations were performed with three distinct sets of emission fields. The first two scenarios simulate actual 2002 and 2004 emissions as best inferred from available emission data. These scenarios characterize emissions before and after implementation of the NOx SIP Call, respectively. The third scenario represents a hypothetical rendering of NOx emissions in 2002 had there been no emission controls imposed on the utility sector. All components of the no control scenario are identical to those of the 2002 scenario,except the point source emissions that were obtained by multiplying the 2002 heat input(electricity demand) with the emission rates (kg NOx emitted/mmBTU utilized) in 1997. The modeling results show that the implementation of the NOx SIP Call led to a decline in the maximum ozone concentrations in most of the eastern US. A decrease ranging from 3% to 5% was widely identifed between the median 8–hr daily maximum concentrations modeled for 2004 and 2002. However, the fourth-highest modeled values decreased by 5 - 8%. Without controls on the utility sector, total emissions in 2002 would have been 40% higher than they actually were in 2002. However, while ozone concentrations would have been higher in most of the domain without the NOx SIP Call, local areas surrounding major sources would actually have had 8-hr daily maximum concentrations 7% to 8% lower.