Response of Fine Particulate Matter to Emission Changes of Oxides of Nitrogen and Anthropogenic Volatile Organic Compounds in the Eastern United States

摘要

A three-dimensional chemical transport model (Particulate Matter Comprehensive Air Quality Model with Extensions [PMCAMx]) is used to investigate changes in fine particle (PM_(2.5)) concentrations in response to 50% emissions changes of oxides of nitrogen (NO_x) and anthropogenic volatile organic compounds (VOCs) during July 2001 and January 2002 in the eastern United States. The reduction of NO_x emissions by 50% during the summer results in lower average oxidant levels and lowers PM_(2.5) (8% on average), mainly because of reductions of sulfate (9-11%), nitrate (45-58%), and ammonium (7-11%). The organic particulate matter (PM) slightly decreases in rural areas, whereas it increases in cities by a few percent when NO_x is reduced. Reduction of NO_x during winter causes an increase of the oxidant levels and a rather complicated response of the PM components, leading to small net changes. Sulfate increases (8-17%), nitrate decreases (18-42%), organic PM slightly increases, and ammonium either increases or decreases a little. The reduction of VOC emissions during the summer causes on average a small increase of the oxidant levels and a marginal increase in PM_(2.5). This small net change is due to increases in the inorganic components and decreases of the organic ones. Reduction of VOC emissions during winter results in a decrease of the oxidant levels and a 5-10% reduction of PM_(2.5) because of reductions in nitrate (4-19%), ammonium (4-10%), organic PM (12-14%), and small reductions in sulfate. Although sulfur dioxide (SO_2) reduction isrnthe single most effective approach for sulfate control, the coupled decrease of SO_2 and NO_x emissions in both seasons is more effective in reducing total PM_(2.5) mass than the SO_2 reduction alone.