No abstract

Air pollution has recently become China's highest environmental issue due to the rapid development of industry and urbanization. So far, the precise sources of air pollution of main cities are unknown. To identify sources, we studied air pollution in the Hangzhou city from November 25 to December 11, 2013, at eight monitoring stations. We analyzed PM 2.5 , PM 10 , O 3 , NO 2 , CO, SO 2 , and satellite observations for aerosol optical thickness (PM: particulate matter). Pollution sources were identified by trajectory clustering and receptor models. The results show that during the weekly heavy haze episode, December 3-9, mean concentrations were 293.4 ± 103.2 lg m -3 for PM 2.5 , 376.8 ± 119.4 lg m -3 for PM 10 , 58.0 ± 37.2 lg m -3 for SO 2 , 118.5 ± 39.3 lg m -3 for NO 2 , and 2,429 ± 740 lg m -3 for CO. The back trajectory cluster analysis indicates that the predominant clusters are south (37.1 %) and southeast (28.6 %) during the weekly heavy haze episode. The results of the receptor models show that the sources affecting formation of the extremely high PM 2.5 in Hangzhou are mainly located in the southeastern coast of Zhejiang and Fujian provinces, north part of Jiangxi, and central part of Jiangsu province. Rather than local emissions, it is also found that air mass pathways and cross-border transports control high PM 2.5 concentrations and formation in Hangzhou. Therefore, it is necessary to implement air pollution control for all industrial areas at local, regional, and national scales in China.

Wuhan city requires a 5% reduction of the annual mean of PM concentration by the end of 2017. In order to accomplish this goal, Wuhan has adopted some measures to improve its air quality. This work has determined the main pollution sources that affect the formation of haze in Wuhan by transport. We showed that apart from the local emissions, north and south of Wuhan were the potential sources contributing to the high PM concentrations in Wuhan, such as Baoding and Handan in Hebei province, Zhumadian and Jiaozuo in Henan province, and Changsha and Zhuzhou in Hunan province.

Abstract. To evaluate the effect of temporary emission control measures on air quality during the 2016 G20 summit held in Hangzhou, China, an intensive field campaign was conducted with a focus on aerosol chemistry and gaseous precursors from 15 August to 12 September 2016. The concentrations of fine particles were reduced during the intense emission control stages, with the reduction of carbonaceous matter being mostly responsible for this observed decrease. This, in turn, was mainly ascribed to the decrease of secondary organic aerosols via the suppression of daytime peak secondary organic carbon (SOC)formation. Although the regional joint control was enacted extending to the Yangtze River Delta region, the effect of long-range transport on the air quality of Hangzhou was ubiquitous. Unexpectedly high NOx concentrations were observed during the control stage, when the strictest restriction on vehicles was implemented, owing to contributions from upstream populous regions such as Jiangsu and Shandong provinces. In addition, the continental outflow traveling over the ocean triggered a short pollution episode on the first day of the G20 summit, resulting in a significant enhancement of the nitrogen/sulfur oxidation rates. In the wake of the summit, all air pollutants evidently rebounded after the various control measures were lifted. Overall, the fraction of secondary inorganic aerosols (SIA; in this case sulfate, nitrate, and ammonium aerosols – SNA) in PM2.5 increased as relative humidity increased; however, the overall concentration of PM2.5 did not increase. Aerosol components that had distinctly different sources and formation mechanisms, e.g., sulfate/nitrate and elemental carbon, exclusively showed strong correlations during the regional/long-range transport episodes. The sulfate, nitrate, and ammonium to elemental carbon (SNA∕EC) ratio, which was used as a proxy for assessing the extent of secondary inorganic aerosol formation, was found to be significantly enhanced under transport conditions from northern China. This study highlighted that emission control strategies were beneficial for curbing particulate pollution, in addition to the fact that regional/long-range transport may offset local emission control effects to some extent.

No abstract