Widespread and persistent ozone pollution in eastern China during the non-winter season of 2015: observations and source attributions

Other literature type English OPEN
Li, Guohui ; Bei, Naifang ; Cao, Junji ; Wu, Jiarui ; Long, Xin ; Feng, Tian ; Dai, Wenting ; Liu, Suixin ; Zhang, Qiang ; Tie, Xuexi (2017)

Rapid growth of industrialization, transportation, and urbanization has caused increasing emissions of ozone (O<sub>3</sub>) precursors recently, enhancing the O<sub>3</sub> formation in eastern China. We show here that eastern China has experienced widespread and persistent O<sub>3</sub> pollution from April to September 2015 based on the O<sub>3</sub> observations in 223 cities. The observed maximum 1 h O<sub>3</sub> concentrations exceed 200 µg m<sup>−3</sup> in almost all the cities, 400 µg m<sup>−3</sup> in more than 25 % of the cities, and even 800 µg m<sup>−3</sup> in six cities in eastern China. The average daily maximum 1 h O<sub>3</sub> concentrations are more than 160 µg m<sup>−3</sup> in 45 % of the cities, and the 1 h O<sub>3</sub> concentrations of 200 µg m<sup>−3</sup> 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, SO<sub>2</sub>, NO<sub>2</sub>, and PM<sub>2.5</sub> from April to September in eastern China have considerably decreased, but the O<sub>3</sub> concentrations have increased by 9.9 %. A widespread and severe O<sub>3</sub> 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 O<sub>3</sub> contribution of biogenic and various anthropogenic sources. The model generally performs reasonably well in simulating the temporal variations and spatial distributions of near-surface O<sub>3</sub> concentrations. Using the factor separation approach, sensitivity studies have indicated that the industry source plays the most important role in the O<sub>3</sub> formation and constitutes the culprit of the severe O<sub>3</sub> pollution in eastern China. The transportation source contributes considerably to the O<sub>3</sub> formation, and the O<sub>3</sub> contribution of the residential source is not significant generally. The biogenic source provides a background O<sub>3</sub> source, and also plays an important role in the south of eastern China. Further model studies are needed to comprehensively investigate O<sub>3</sub> formation for supporting the design and implementation of O<sub>3</sub> 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.
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