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

摘要

Rapid growth of industrialization, transportation, and urbanization has caused increasing emissions of ozone (Osub3/sub) precursors recently, enhancing the Osub3/sub formation in eastern China. We show here that eastern China has experienced widespread and persistent Osub3/sub pollution from April to September 2015 based on the Osub3/sub observations in 223 cities. The observed maximum 1?h Osub3/sub concentrations exceed 200?μg?msup?3/sup in almost all the cities, 400?μg?msup?3/sup in more than 25?% of the cities, and even 800?μg?msup?3/sup in six cities in eastern China. The average daily maximum 1?h Osub3/sub concentrations are more than 160?μg?msup?3/sup in 45?% of the cities, and the 1?h Osub3/sub concentrations of 200?μg?msup?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, SOsub2/sub, NOsub2/sub, and PMsub2.5/sub from April to September in eastern China have considerably decreased, but the Osub3/sub concentrations have increased by 9.9?%. A widespread and severe Osub3/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 Osub3/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 Osub3/sub concentrations. Using the factor separation approach, sensitivity studies have indicated that the industry source plays the most important role in the Osub3/sub formation and constitutes the culprit of the severe Osub3/sub pollution in eastern China. The transportation source contributes considerably to the Osub3/sub formation, and the Osub3/sub contribution of the residential source is not significant generally. The biogenic source provides a background Osub3/sub source, and also plays an important role in the south of eastern China. Further model studies are needed to comprehensively investigate Osub3/sub formation for supporting the design and implementation of Osub3/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.