Using air quality modeling to study source-receptor relationships between nitrogen oxides emissions and ozone exposures over the United States.
Human exposure to ambient ozone (O(3)) has been linked to a variety of adverse health effects. The ozone level at a location is contributed by local production, regional transport, and background ozone. This study combines detailed emission inventory, air quality modeling, and census data to investigate the source-receptor relationships between nitrogen oxides (NO(x)) emissions and population exposure to ambient O(3) in 48 states over the continental United States. By removing NO(x) emissions from each state one at a time, we calculate the change in O(3) exposures by examining the difference between the base and the sensitivity simulations. Based on the 49 simulations, we construct state-level and census region-level source-receptor matrices describing the relationships among these states/regions. We find that, for 43 receptor states, cumulative NO(x) emissions from upwind states contribute more to O(3) exposures than the state's own emissions. In-state emissions are responsible for less than 15% of O(3) exposures in 90% of U.S. states. A state's NO(x) emissions can influence 2 to 40 downwind states by at least a 0.1 ppbv change in population-averaged O(3) exposure. The results suggest that the U.S. generally needs a regional strategy to effectively reduce O(3) exposures. But the current regional emission control program in the U.S. is a cap-and-trade program that assumes the marginal damage of every ton of NO(x) is equal. In this study, the average O(3) exposures caused by one ton of NO(x) emissions ranges from -2.0 to 2.3 ppm-people-hours depending on the state. The actual damage caused by one ton of NO(x) emissions varies considerably over space.
Tong
Daniel Q
DQ
Science and Technology Corporation, Research Triangle Park, NC 27711, USA. tong.daniel@epa.gov
Muller
Nicholas Z
NZ
Kan
Haidong
H
Mendelsohn
Robert O
RO
D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data; D001272:Atmosphere / Q000737:chemistry*; D019352:Censuses; D004781:Environmental Exposure / Q000032:analysis*; D004784:Environmental Monitoring; D006801:Humans; D008956:Models, Chemical; D009589:Nitrogen Oxides / Q000032:analysis*; D010126:Ozone / Q000032:analysis*; D014481:United States
D000393:Air Pollutants; D009589:Nitrogen Oxides; D010126:Ozone