Dramatic changes in atmospheric pollution source contributions for a coastal megacity in northern China from 2011 to 2020

Abstract

Abstract. Understanding the effectiveness of long-term air pollution regulatory measures is important for control policy formulation. Efforts have been made using chemical transport modelling and statistical approaches to evaluate the efficacy of the Clean Air Action Plan (CAAP; 2013–2017) and the Blue Sky Protection Campaign (BSPC; 2018–2020) enacted in China. Changes in air quality due to reduction in emissions can be masked by meteorology, making it highly challenging to reveal the real effects of control measures. A knowledge gap still existed with respect to how sources changed before and after the CAAP and BSPC were implemented, respectively, particularly in coastal areas where anthropogenic emissions mixed with additional natural sources (e.g. marine aerosol). This work applied a machine-learning-based meteorological normalization approach to decouple the meteorological effects from air quality trend in a coastal city in northern China (Qingdao). Secondly, the relative changes in source contributions to ambient PM2.5 with a ∼ 10-year observation interval (2011–2012, 2016, and 2019) were also investigated. We discovered that the largest emission reduction section was likely from coal combustion as the meteorologically normalized SO2 dropped by ∼ 15.5 % yr−1, and the annual average dispersion-normalized SO42- decreased by ∼ 41.5 %. Change in the meteorologically normalized NO2 was relatively stable (∼ 1.0 % yr−1), and NO3- changed inappreciably in 2016–2019 but was significantly higher than that prior to the CAAP. Crustal dust decreased remarkably after the CAAP began. Industrial emissions, for example, steel-related smelting, decreased after 2016 due to the relocation of steel-making enterprises. Note that vehicle emissions were increased in importance as opposed to the other primary sources. Similar to other megacities, Qingdao is also at risk of increased ozone pollution that in turn facilitates secondary-particle formation in the future. The policy assessment approaches applied in this work also work for other places where air quality management is highly in demand to reduce air pollution.

Quantifying vehicle restriction related PM2.5 reduction using field observations in an isolated urban basin

“…Primary vehicle emissions, secondary formation, and mineral dust were the main contributors to PM 2.5 . The contribution of primary sources such as primary vehicle emissions, and mineral dust in Lanzhou was higher than the megacities such as Beijing [54], and Qingdao [8], whereas the secondary formation was lower than in these cities. The result shows that secondary formation is predominant in megacities, while the primary vehicle emissions are predominant in semi-arid regions.…”

“…The sources of PM 2.5 , and their contributions, have changed significantly with the development of society and economy. Industrial emissions have declined over the past few years, whereas vehicle emissions have increased [6][7][8][9][10]. Because of the increasing number of vehicles [11], vehicle emissions have become an important source of PM 2.5 in many cities, especially in the developed countries in recent years [12][13][14][15][16].…”

Measuring the Emission Changes and Meteorological Dependence of Source‐Specific BC Aerosol Using Factor Analysis Coupled With Machine Learning

“…The factor of VE is composed primarily of OC (37%) and NO 2 (24%) with narrow DISP bounds. Vehicular emissions is a major source of OC and NO 2 (Bi et al., 2019; B. S. Liu et al., 2022; H. K. Liu et al., 2022; Zotter et al., 2017). The percentage of light absorption showed an increasing trend from 370 to 880 nm (Figure 3), which is consistent with previous reports (H. K. Liu et al., 2021, 2022; Yuan et al., 2022).…”

“…There has been a recent explosion of work on decoupling meteorology and emissions from air quality time series using the machine learning regression‐based weather normalization (deweathering) technique (Grange & Carslaw, 2019; Grange et al., 2018). The deweathered concentrations of air pollutants successfully tracked emission changes owing to policy interventions such as the COVID‐19 lockdowns (e.g., Dai et al., 2021b; Grange et al., 2021; B. S. Liu et al., 2022; Shi et al., 2021; Zhou et al., 2022). Therefore, combining PMF with the deweathering techniques can provide more practical implications for air quality management.…”

Impact of Clean Air Policy on Criteria Air Pollutants and Health Risks Across China During 2013–2021

“…Liu et al (2018) estimated that the mortality of chronic obstructive pulmonary disease (COPD) due to overproof ozone exposure in China in 2015 reached 80,280 cases. Fortunately, Chinese government has imposed strict emission control measures including the Clean Air Action Plan (CAAP;2013 and the Blue-Sky Protection Campaign (BSPC; 2018-2020) to alleviate the PM 2.5 and O 3 pollution coordinately (Dong et al, 2022;Liu et al, 2022). However, the impact of these emission control measures on air quality improvement in China was not very clear, which was very important for control policy formulation and implementation.…”