key: cord-0786120-jfscgoi9 authors: Jia, Haohao; Huo, Juntao; Fu, Qingyan; Duan, Yusen; Lin, Yanfen; Jin, Xiaodan; Hu, Xue; Cheng, Jinping title: Insights into chemical composition, abatement mechanisms and regional transport of atmospheric pollutants in the Yangtze River Delta region, China during the COVID-19 outbreak control period() date: 2020-09-09 journal: Environ Pollut DOI: 10.1016/j.envpol.2020.115612 sha: 65a4094ac14b958698b231715e6773e17b048c51 doc_id: 786120 cord_uid: jfscgoi9 To investigate chemical characteristics, abatement mechanisms and regional transport of atmospheric pollutants during the COVID-19 outbreak control period in the Yangtze River Delta (YRD) region, China, the measurements of air pollutants including fine particulate matter (PM(2.5)) and volatile organic compounds (VOCs) on non-control period (NCP, 24 December, 2019–23 January, 2020) and control period (CP, 24 January–23 February, 2020) were analyzed at the urban Pudong Supersite (PD) and the regional Dianshan Lake Supersite (DSL). Due to the stricter outbreak control, the levels of PM(2.5) and VOCs, and the occurrence frequencies of haze-fog episodes decreased substantially from NCP to CP, with average reduction rates of 31.6%, 38.9% and 35.1% at PD, and 34.5%, 50.7% and 37.9% at DSL, respectively. The major source for PM(2.5) was secondary sulfate & nitrate in both periods, and the emission control of primary sources such as coal burning and vehicle exhaust decreased the levels of precursors gas sulfur dioxide and nitrogen oxide, which highly contributed to the abatement of PM(2.5) from NCP to CP. The higher levels of ozone at both PD and DSL on CP might be due to the weak nitrogen monoxide titration, low relative humidity and high visibility compared with NCP. Vehicle exhaust and fugitive emission from petrochemical industry were the major contributors of ambient VOCs and their decreasing activities mainly accounted for VOCs abatement. Moreover, the high frequency of haze-fog events was closely impacted by medium-scale regional transport within Anhui and Jiangsu provinces. Therefore, the decreasing regional transported air pollutants coincided with the emission control of local sources to cause the abatement of haze-fog events in YRD region on CP. This study could improve the understanding of the change of atmospheric pollutants during the outbreak control period, and provide scientific base for haze-fog pollution control in YRD region, China. Atmospheric pollution has aroused global concern due to the presence of harmful particles and visibility was applied to characterize the pollution levels, which was generally classified into five 126 categories: ≥10 km, clear; ≥ 5.0 km, and < 10 km, slight fog-haze (SFH); ≥ 3.0 km, and < 5.0 km, 127 low fog-haze (LFH); ≥ 2.0 km, and < 3.0 km, medium fog-haze (MFH); < 2.0 km, heavy fog-haze 128 (HFH). Primary OC (POC) and secondary OC (SOC) were estimated using EC as a tracer by the 155 following relation (Turpin and Huntzicker, 1995) : conversion factor for atmospheric aerosols is 1.6 suggested by Turpin and Lim (2001 The average data for 17 elements during the two periods at PD and DSL are depicted in Fig. S6 . NOR showed the similar variations with SOR on PD and DSL on each period (Fig. S9) . The relative contributions of six sources for PM 2.5 at PD and DSL on two periods are showed in Fig. 4a , and the source identification of PM 2.5 is provided in Supplemental materials. The statistics of 56 VOC species measured at PD and DSL during the NCP and CP are depicted 343 in Fig. S10 . The hourly concentrations of Σ 56 VOCs were 23.9 ± 12.6 ppbv and 14.6 ± 7.05 ppbv at Alkanes were the major components of VOCs at both PD and DSL for two periods, with the mean 347 contribution rates of 70.2% and 60.6% on NCP, and 76.7% and 64.9% on CP, respectively. As 348 showed in Fig. S11 , the top ten abundant components of VOCs at PD were consistent with those of 349 DSL for NCP and CP, respectively, which 9 of 10 species were also the same on two periods. 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