Variation of atmospheric PCDD/Fs associated with haze: Implications from temporary large-scale emission controls

Increased anthropogenic activities have contributed to the deteriorating air quality of Beijing in recent years. During the period of November 2014, we collected 90 air samples in the urban and rural sites of Beijing to... [ view full abstract ]

Increased anthropogenic activities have contributed to the deteriorating air quality of Beijing in recent years. During the period of November 2014, we collected 90 air samples in the urban and rural sites of Beijing to investigate the variations of PCDD/Fs before, during and after the APEC summit. The effectiveness of emission-control measures on reducing atmospheric pollution of POPs was assessed. The air concentrations of PCDD/Fs at the urban sites were in the range of 0.29-177 pg m-3, which is clearly higher than the rural site (0.02-69 pg m-3). This urban-rural concentration gradient demonstrated urban areas as emission sources of PCDD/Fs to the ambient air and can be explained by the lower population density, sparse traffic and fewer industrial activities in the rural area. The air concentrations of PCDD/Fs during the APEC was the lowest, showing a ~70% reduction from one week before the summit. Haze days corresponded to high elevation of PCDD/Fs, showing the highest of 17 folds from non-haze days. In non-haze days, the TEQs of PCDD/Fs averaged 0.23 pg WHO-TEQ m-3, lower than the air quality guideline of 0.6 pg TEQ m-3 proposed by Japan government. However, in haze days, the TEQs of PCDD/Fs averaged 3.4 pg WHO-TEQ m-3, obviously higher than non-haze days.