HR: 16:00h
AN: A34B-01    [Abstracts]
TI: Summertime State-Level Source-Receptor Relationships between NOx Emissions and Downwind Surface Ozone Concentrations over the Continental United States
AU: Tong, D Q
EM: tong.daniel@epamail.epa.gov
AF: Princeton University, Woodrow Wilson School of Public and International Affairs, Princeton, NJ 08544, United States
AU: Tong, D Q
EM: tong.daniel@epamail.epa.gov
AF: Now at Science and Technology Corporation, On assignment to USA EPA, Mail Drop E243- 03, RTP, NC 27711, United States
AU: Tong, D Q
EM: tong.daniel@epamail.epa.gov
AF: North Carolina State University, Department of Marine, Earth and Atmospheric Sciences, Raleigh, NC 27607,
AU: * Mauzerall, D L
EM: mauzeral@princeton.edu
AF: Princeton University, Woodrow Wilson School of Public and International Affairs, Princeton, NJ 08544, United States
AB: Inter-state transport of ozone (O3) and its precursors can contribute substantially to state-level surface O3 concentrations, making it difficult for some states to meet the National Ambient Air Quality Standard (NAAQS) for O3 by limiting only their own emissions. This study uses the Community Multiscale Air Quality (CMAQ) model to analyze the effect of inter-state transport of O3 and its precursors on surface O3 in summer over each continental U.S. state. By examining the difference between a standard model simulation and perturbation simulations in which each state's NOx emissions are removed, we establish for the first time a summertime source-receptor matrix for all 48 continental states. The NAAQS requires surface O3 concentrations to not exceed 0.08ppm O3 averaged over an 8-hour period. We find that for 16 states at least one neighboring state's NOx emissions are responsible for a larger increase in peak 8-hour average surface O3 concentrations than the state's own emissions. For 80% of the contiguous states, inter-state transport is more important than local emissions for summertime 8-hour peak O3 concentrations. The large influence we find for out-of-state emissions on peak 8- hour O3 demonstrates the difficulty that some states found to be in violation of the 8-hour NAAQS for O3 may have in reaching compliance simply by controlling their own NOx emissions. To quantify the impact of NOx emissions from a single source state on surface O3 concentrations outside that state, we calculate an out-of-state influence ratio. This influence ratio is the percentage change in surface O3 outside the source state relative to the total change in surface O3 across the continental United States due to the NOx emissions from the source state. The influence ratio for peak 8-hour O3 is over 30% in all states except ME and VT, over 50% in 30 states, and over 70% in 11 states. EPA recognized the importance of inter-state transport when developing the Clean Air Interstate Rule (CAIR). Our source-receptor matrices indicate that the geographical range of the CAIR program is sufficient to address interstate transport of O3 in most of the states included in the program. However, the exclusion of TX, which has particularly large NOx emissions, from the CAIR O3 program leaves emission sources uncontrolled that contribute to over one third of peak O3 increases in four participating downwind states.
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0368 Troposphere: constituent transport and chemistry
DE: 6615 Legislation and regulations (6324)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting