In recent years, Beijing has experienced severeair pollution which has caused widespread public concern.Compared to the same period in 2014, the first threequarters of 2015 exhibited significantly improved airquality....In recent years, Beijing has experienced severeair pollution which has caused widespread public concern.Compared to the same period in 2014, the first threequarters of 2015 exhibited significantly improved airquality. However, the air quality sharply declined in thefourth quarter of 2015, especially in November andDecember. During that time, Beijing issued the first redalert for severe air pollution in history. In total, 2 red alerts,3 orange alerts, 3 yellow alerts, and 3 blue alerts wereissued based on the adoption of relatively temporaryemergency control measures to mitigate air pollution. Thisstudy explored the reasons for these variations in airquality and assessed the effectiveness of emergency alertsin addressing severe air pollution. A synthetic analysis ofemission variations and meteorological conditions wasperformed to better understand these extreme air pollutionepisodes in the fourth quarter of 2015. The results showedthat compared to those in the same period in 2014, thedaily average emissions of air pollutants decreased in thefourth quarter of 2015. However, the emission levels ofprimary pollutants were still relatively high, which was themain intrinsic cause of haze episodes, and unfavorablemeteorological conditions represented important externalfactors. Emergency control measures for heavy airpollution were implemented during this red alert period,decreasing the emissions of primary air pollutants byapproximately 36% and the PMa.5 concentration by 11%-21%.展开更多
文摘In recent years, Beijing has experienced severeair pollution which has caused widespread public concern.Compared to the same period in 2014, the first threequarters of 2015 exhibited significantly improved airquality. However, the air quality sharply declined in thefourth quarter of 2015, especially in November andDecember. During that time, Beijing issued the first redalert for severe air pollution in history. In total, 2 red alerts,3 orange alerts, 3 yellow alerts, and 3 blue alerts wereissued based on the adoption of relatively temporaryemergency control measures to mitigate air pollution. Thisstudy explored the reasons for these variations in airquality and assessed the effectiveness of emergency alertsin addressing severe air pollution. A synthetic analysis ofemission variations and meteorological conditions wasperformed to better understand these extreme air pollutionepisodes in the fourth quarter of 2015. The results showedthat compared to those in the same period in 2014, thedaily average emissions of air pollutants decreased in thefourth quarter of 2015. However, the emission levels ofprimary pollutants were still relatively high, which was themain intrinsic cause of haze episodes, and unfavorablemeteorological conditions represented important externalfactors. Emergency control measures for heavy airpollution were implemented during this red alert period,decreasing the emissions of primary air pollutants byapproximately 36% and the PMa.5 concentration by 11%-21%.
