Integrated observational and modeling approaches forevaluating the effectiveness of ozone control policies

摘要

Although there has been much progress in improving ambient airquality, the concentrations of ozone continue to exceed theiracceptable levels in the United States and many parts of the world.Because of the regional nature of this pollutant, the U.S. Environ-mental Protection Agency (EPA) required the States to undertakelarge reductions in nitrogen oxides (NO_x) emissions by 2004 to ad-dress long-range transport of ozone and its precursors as part oftheir State Implementation Plans (SIPS). As a result of this controlprogram, referred to as the "NO_x SIP Call", 21 states in the easternUnited States have achieved substantial NO_x reductions from theutility sector by 2004. This emission control strategy should greatlyreduce ambient ground-level ozone in the eastern United States.A systematic tracking of air quality achievements is necessary toproperly evaluate U.S. policy and program results in protectingpublic health and the environment. Consequently, EPA has under-taken a comprehensive assessment of the effectiveness of this controlprogram to meet its objectives. In this paper, integrated obser-vational and modeling methodologies are described in order to assessthe impact of NO_x emission reductions on maximum ozone concen-trations. In particular, the emphasis in this paper is on selectedresults from the photochemical modeling effort. A set of modelingscenarios was performed that included point source NO,, emissionmeasurements from extended summer periods before and afterimplementation of the emission reductions.