Abstract
The Beijing government implemented a number of clean air action plans to improve air quality in the last 10 years, which contributed to changes in the concentration of fine particles and their compositions. However, quantifying the impacts of these interventions is challenging as meteorology masks the real changes in observed concentrations. Here, we applied a machine learning technique to decouple the effect of meteorology and evaluate the changes in the chemistry of nonrefractory PM1 (particulate matter less than 1 μm) in winter 2007, 2016, and 2017 as a result of the clean air actions. The observed mass concentrations of PM1 were 74.6, 90.2, and 36.1 μg m-3 in the three winters, while the deweathered concentrations were 74.2, 78.7, and 46.3 μg m-3, respectively. The deweathered concentrations of PM1, organics, sulfate, ammonium, chloride, SO2, NO2, and CO decreased by -38, -46, -59, -24, -51, -89, -16, and -52% in 2017 in comparison to 2007. On the contrary, the deweathered concentration of nitrates increased by 4%. Our results indicate that the clean air actions implemented in 2017 were highly effective in reducing ambient concentrations of SO2, CO, and PM1 organics, sulfate, ammonium, and chloride, but the control of nitrate and PM1 organics remains a major challenge.
Highlights
Frequent haze pollution in China has drawn great attention because of its adverse impacts on visibility, public health,[1] and complex interaction with the climate.[2]
Our results indicate that the clean air actions implemented in 2017 were highly effective in reducing ambient concentrations of SO2, CO, and PM1 organics, sulfate, ammonium, and chloride, but the control of nitrate and PM1 organics remains a major challenge
By the end of 2017, coal-fired boilers with a capacity below 7 MW in the whole city and those with a capacity below 25 MW were basically eliminated in urban areas; there is no longer coal combustion in industry fields, and no residential coal use in the core area in the six districts and the southern plains.[9]
Summary
Frequent haze pollution in China has drawn great attention because of its adverse impacts on visibility, public health,[1] and complex interaction with the climate.[2]. Most important regulations were related to energy system restructuring and vehicle emissions.[8] Because coal combustion has always been a major air pollution source in Beijing, many interventions were put into place to reduce the air pollutant emissions from this source. These include the desulfurization retrofit, coal to gas in urban areas and denitrification retrofit for power plants since 2005, reduced coal combustion by nearly 11 million tons by 2017, and renovation of coal-fired boilers and old one-story houses in core areas in the mid-2000s. Focusing on new Received: August 2, 2019 Revised: November 21, 2019 Accepted: November 26, 2019 Published: November 26, 2019
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