Effect of emission control measures on ozone concentrations in Hangzhou during G20 meeting in 2016

Abstract

The effect of emission control measures on ozone (O3) concentrations in Hangzhou during G20 (The Group of Twenty Finance Ministers and Central Bank Governors) meeting during 24 August to 6 September of 2016 was evaluated using the nested version of a global chemical transport model. During G20, observed concentrations of PM10, PM2.5, SO2, NO2, and CO were all below national air quality standards, whereas those of MDA8 O3 were above national standard (with an averaged value of 160.2 μg m−3) but had a decreasing trend. Model sensitivity studies show that, MDA8 O3 concentrations in Hangzhou during G20 were reduced by 11.3 μg m−3 (6.8%), 14.8 μg m−3 (8.9%), and 19.5 μg m−3 (11.7%) with emission control measures in the core area, Zhejiang province, and the Yangtze River Delta (YRD) region, respectively, indicating that control measures were the most effective when carried out jointly in YRD. Considering the ratios of NOx to VOCs during G20, Hangzhou and most areas of Zhejiang province were in transitional regime; reductions in either NOx or VOCs could reduce O3 concentrations. We also quantified how sensitive O3 concentrations respond to emission reductions in sectors of industry, power, residential and transportation in the whole of YRD during G20. The removal of emissions in industry and transportation sectors would lead to the largest reductions of 17.6 μg m−3 (10.5%) and 12.3 μg m−3 (7.4%) in MDA8 O3 concentrations in Hangzhou during G20, respectively. This study has important implications for the control of high O3 levels in eastern China.