Part II: PM2.5 and Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) in the Ambient Air of Northern China

ABSTRACTThe atmospheric PM2.5, PM2.5/PM10, PCDD/Fs-WHO2005-TEQ, and PCDD/F (polychlorinated dibenzo-p-dioxins and dibenzofuran) phase distributions of 23 cities in southern China, during 2014–2016, were investigated in this study. In general, the cities with higher latitudes had higher PM2.5 concentrations than those with lower latitudes. During 2014–2016, the lowest three-year average concentrations of PM2.5 occurred at Sanya and Haikou and were 16.4 and 21.7 µg m–3, respectively; while the highest concentrations of PM2.5 was occurred at Wuhan and Luzhou and were 68.8 and 63.1 µg m–3, respectively. During 2015–2016, the PM2.5 concentrations of most of cities decreased, but those of five cities (Chengdu, Luzhou, Nanchang, Qujing and Quanzhou) increased, indicting that the air quality of these five cities was still not well controlled. The average RM values of the 23 cities were 5.20, 4.49 and 4.13 in 2014, 2015 and 2016, respectively, which revealed that the PM2.5 concentrations in the cities of southern China slowly decreased, although they were still far above the WHO air quality regulated standard (10 µg m–3). In general, a city with a higher PM2.5 concentration was also had a higher PM2.5/PM10 ratio. Among the 23 cities, the six highest three-year averages of total-PCDD/Fs-WHO2005-TEQ concentrations were 0.0665, 0.0633, 0.0625, 0.0600, 0.0528 and 0.0526 pg-WHO2005-TEQ m–3 in Chengdu, Wuhan, Nanjing, Hefei, Luzhou and Hangzhou, respectively. During 2014, the six cities (Hefei, Nanjing, Wuhan, Guiyang, Shanghai and Chengdu) with the lowest temperatures in winter (an average of 5.4°C), their average particle phase fractions of total-PCDD/Fs-WHO2005-TEQ that were approximately 76%, 53%, 71% and 93% in the spring, summer, fall and winter, respectively; while, the six cities (Haikou, Fuzhou, Guangzhou, Nanning, Nanchang and Changsha) with the highest temperatures in summer (an average of 16.5°C), had average particle phase fractions of total-PCDD/Fs-WHO2005-TEQ that were approximately 61%, 42%, 57% and 81% in the spring, summer, fall and winter, respectively. The results of this study provide information showing the trends of both atmospheric PM2.5 and PCDD/Fs in the cities of southern China. In addition, this study provided the overview relating to the PM2.5 and PCDD/Fs in ambient air of southern China, which was not reported in previous studies. The results of this study were of great importance to present the trends of air quality in China. It is also useful for the establishment of control strategies in the future.