Abstract
Air pollution in Beijing, China has attracted continuous worldwide public attention along with the rapid urbanization of the city. By implementing a set of air pollution mitigation measures, the air quality of Beijing has been gradually improved in recent years. In this study, the intrinsic factors leading to air quality improvement in Beijing are studied via a quantitative evaluation of the temporal and spatial changes in emissions of primary air pollutants over the past ten years. Based on detailed activity levels of each economic sector and a localized database containing source and pollutant specific emission factors, an integrated emissions inventory of primary air pollutants discharged from various sources between 2006 and 2015 is established. With the implementation of phased air pollution mitigation measures, and the Clean Air Action Plan, the original coal-dominated energy structure in Beijing has undergone tremendous changes, resulting in the substantial reduction of multiple air pollutants. The total of emissions of six major atmospheric pollutants (PM10, PM2.5, SO2, NOX, VOCs and NH3) in Beijing decreased by 35% in 2015 compared to 2006—this noticeable decrease was well consistent with the declining trend of ambient concentration of criterion air pollutants (SO2, PM10, PM2.5 and NO2) and air quality improvement, thus showing a good correlation between the emission of air pollutants and the outcome of air quality. SO2 emission declined the most, at about 71.7%, which was related to the vigorous promotion of combustion source control, such as the shutdown of coal-fired facilities and domestic stoves and transition to clean energy, like natural gas or electricity. Emissions of PM decreased considerably (by 48%) due to energy structure optimization, industrial structure adjustments, and end-of-pipe PM source control. In general, NOX, NH3, and VOCs decreased relatively slightly, by 25%, 14%, and 2%, respectively, and accordingly, they represented the limiting factors for improving air quality and the key points of air pollution mitigation in Beijing for the future.
Highlights
Owing to the rapid growth of the regional economy and population, a substantial amount of energy has been consumed in Beijing
To determine the causes and key factors contributing to the improvement of air quality, this study quantitatively evaluated the variations in air pollutant emissions in Beijing
nitrogen oxides (NOX) emissions declined to a small extent due to various factors, which was mainly because pollutant emission reductions achieved by the control of coal combustion were partially offset by the increase in pollutant emissions resulting from the rapid increase in natural gas consumption and the number of motor vehicles
Summary
Owing to the rapid growth of the regional economy and population, a substantial amount of energy has been consumed in Beijing. Atmosphere 2019, 10, 494 expansion have led to a large number of motor vehicles and consistently enormous construction areas in Beijing [1,2,3]. These activities consume considerable amounts of fossil fuels, dominated by high-polluting coal, resulting in relatively massive air pollutant emissions into the atmosphere. Since 1998, Beijing has continuously issued 16 phases of air pollution mitigation measures and the Clean Air Action Plan (2013–2017), as well as a set of specific measures, including adjusting and improving the coal-dominated energy structure, comprehensive motor vehicle pollution control, industrial restructuring, and strengthening education and awareness on ecological protection and public environments [10,11]. The annual average concentration of PM2.5 was still as high as 58 μg/m3 in
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