Projections of air pollutant emissions and its impacts on regional air quality in China in 2020

Anthropogenic emissions of air pollutants in China influence not only local and regional environments but also the global atmospheric environment; therefore, it is important to understand how China's air pollutant emissions will change and how they will affect regional air quality in the future. Emission scenarios in 2020 were projected using forecasts of energy consumption and emission control strategies based on emissions in 2005, and on recent development plans for key industries in China. We developed four emission scenarios: REF[0] (current control legislations and implementation status), PC[0] (improvement of energy efficiencies and current environmental legislation), PC[1] (improvement of energy efficiencies and better implementation of environmental legislation), and PC[2] (improvement of energy efficiencies and strict environmental legislation). Under the REF[0] scenario, the emission of SO<sub>2</sub>, NO<sub>x</sub>, VOC and NH<sub>3</sub> will increase by 17%, 50%, 49% and 18% in 2020, while PM<sub>10</sub> emissions will be reduced by 10% over East China, compared to that in 2005. In PC[2], sustainable energy polices will reduce SO<sub>2</sub>, NO<sub>x</sub> and PM<sub>10</sub> emissions by 4.1 Tg, 2.6 Tg and 1.8 Tg, respectively; better implementation of current control policies will reduce SO<sub>2</sub>, NO<sub>x</sub> and PM<sub>10</sub> emission by 2.9 Tg, 1.8 Tg, and 1.4 Tg, respectively; strict emission standards will reduce SO<sub>2</sub>, NO<sub>x</sub> and PM<sub>10</sub> emissions by 3.2 Tg, 3.9 Tg, and 1.7 Tg, respectively. Under the PC[2] scenario, SO<sub>2</sub> and PM<sub>10</sub> emissions will decrease by 18% and 38%, while NO<sub>x</sub> and VOC emissions will increase by 3% and 8%, compared to that in 2005. Future air quality in China was simulated using the Community Multi-scale Air Quality Model (CMAQ). Under REF[0] emissions, compared to 2005, the surface concentrations of SO<sub>2</sub>, NO<sub>2</sub>, hourly maximum ozone in summer, PM<sub>2.5</sub>, total sulfur and nitrogen depositions will increase by 28%, 41%, 8%, 8%, 19% and 25%, respectively, over east China. Under the PC[2] emission scenario, the surface concentrations of SO<sub>2</sub>, PM<sub>2.5</sub>, total sulfur depositions will decrease by 18%, 16% and 15%, respectively, and the surface concentrations of NO<sub>2</sub>, nitrate, hourly maximum ozone in summer, total nitrogen depositions will be kept as 2005 level, over east China. The individual impacts of SO<sub>2</sub>, NO<sub>x</sub>, NH<sub>3</sub>, NMVOC and primary PM emission changes on ozone and PM<sub>2.5</sub> concentrations have been analyzed using sensitivity analysis. The results suggest that NO<sub>x</sub> emission control need to be enhanced during the summertime to obtain both ozone and PM<sub>2.5</sub> reduction benefits. NH<sub>3</sub> emission controls should also be considered in order to reduce both nitrate concentration and total nitrogen deposition in the future