Abstract
Abstract. Rapid growth of industrialization, transportation, and urbanization has caused increasing emissions of ozone (O3) precursors recently, enhancing the O3 formation in eastern China. We show here that eastern China has experienced widespread and persistent O3 pollution from April to September 2015 based on the O3 observations in 223 cities. The observed maximum 1 h O3 concentrations exceed 200 µg m−3 in almost all the cities, 400 µg m−3 in more than 25 % of the cities, and even 800 µg m−3 in six cities in eastern China. The average daily maximum 1 h O3 concentrations are more than 160 µg m−3 in 45 % of the cities, and the 1 h O3 concentrations of 200 µg m−3 have been exceeded on over 10 % of days from April to September in 129 cities. Analyses of pollutant observations from 2013 to 2015 have shown that the concentrations of CO, SO2, NO2, and PM2.5 from April to September in eastern China have considerably decreased, but the O3 concentrations have increased by 9.9 %. A widespread and severe O3 pollution episode from 22 to 28 May 2015 in eastern China has been simulated using the Weather Research and Forecasting model coupled to chemistry (WRF-CHEM) to evaluate the O3 contribution of biogenic and various anthropogenic sources. The model generally performs reasonably well in simulating the temporal variations and spatial distributions of near-surface O3 concentrations. Using the factor separation approach, sensitivity studies have indicated that the industry source plays the most important role in the O3 formation and constitutes the culprit of the severe O3 pollution in eastern China. The transportation source contributes considerably to the O3 formation, and the O3 contribution of the residential source is not significant generally. The biogenic source provides a background O3 source, and also plays an important role in the south of eastern China. Further model studies are needed to comprehensively investigate O3 formation for supporting the design and implementation of O3 control strategies, considering rapid changes of emission inventories and photolysis caused by the Atmospheric Pollution Prevention and Control Action Plan released by the Chinese State Council in 2013.
Highlights
In the urban planetary boundary layer (PBL), ozone (O3) is formed as a result of photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxide (NOx) in the presence of sunlight (Brasseur et al, 1999): NO2 + hυ → NO + O 3P (290 nm < λ < 420 nm)O 3P + O2 + M → O3 + MO3 + hυ → O2 + O 1D (290 nm < λ < 329 nm) O 1D + H2O → 2OHOH + VOCs + O2 → RO2 + others RO2 + NO → RO + NO2 where hυ represents the energy of a photon; O 3P and O 1D represent the ground state and electronically excitedPublished by Copernicus Publications on behalf of the European Geosciences Union.G
Continuous deterioration of air quality in China has engendered the implementation of the Atmospheric Pollution Prevention and Control Action Plan, released by Chinese State Council in September 2013 to reduce PM2.5 by up to 25 % by 2017 relative to 2012 levels
Considering the occurrence of high [O3] in the afternoon (12:00–18:00 Beijing time (BJT)), Table 2 provides the average concentrations of air pollutants in the afternoon from April to September in the 65 cites of eastern China in 2013 and 2015
Summary
In the urban planetary boundary layer (PBL), ozone (O3) is formed as a result of photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxide (NOx) in the presence of sunlight (Brasseur et al, 1999): NO2 + hυ → NO + O 3P (290 nm < λ < 420 nm)O 3P + O2 + M → O3 + MO3 + hυ → O2 + O 1D (290 nm < λ < 329 nm) O 1D + H2O → 2OHOH + VOCs + O2 → RO2 + others RO2 + NO → RO + NO2 where hυ represents the energy of a photon; O 3P and O 1D represent the ground state and electronically excitedG. The emissions of O3 precursors, VOCs and NOx, have been significantly increased recently in China due to rapid industrialization and urbanization, and increasing transportation activity (e.g., Zhang et al, 2009; Kurokawa et al, 2013; Yang et al, 2015). Modeling studies have been performed to investigate the O3 pollution in eastern China (Wang et al, 2010; Liu et al, 2012; Situ et al, 2013; Huang et al, 2015). Using the observation-based chemical model, Xue et al (2014) have provided insights into the ozone pollution in Beijing, Shanghai, and Guangzhou by analyzing the O3 precursors and the potential impacts of heterogeneous chemistry
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