Abstract
In this study, the atmospheric total-PCDD/Fs-WHO2005-TEQ concentrations, gas-particle partitioning, PM2.5 concentration, PM2.5-bound total PCDD/Fs-WHO2005-TEQ content and dry deposition flux in Shanghai and Nanjing were investigated from 2018-2020. In Shanghai, the total PCDD/Fs-WHO2005-TEQ concentration dropped from 0.0291 pg-WHO2005-TEQ m–3 from 2018–2019 to 0.0250 pg-WHO2005-TEQ m–3 in 2020, while in Nanjing, it dropped from 0.0423 pg-WHO2005-TEQ m–3 to 0.0338 pg-WHO2005-TEQ m–3. The average concentrations of PCDD/Fs-WHO2005-TEQ in spring and winter in Shanghai and Nanjing were 47.6% and 53.8% higher than those in summer, respectively. From 2018-2019, the average particle phase fractions of total-PCDD/Fs-WHO2005-TEQ in Shanghai and Nanjing were 50.3% and 57.5%, respectively, while in 2020, they were 47.8% and 55.1%, respectively. From 2018-2019, the average PM2.5-bound total PCDD/Fs-WHO2005-TEQ content was 0.342 and 0.493 ng-WHO2005-TEQ g–1 in Shanghai and Nanjing, respectively, while in 2020, it was 0.312 and 0.489 ng-WHO2005-TEQ g–1, respectively. In Shanghai and Nanjing, the average PM2.5-bound total PCDD/Fs-WHO2005-TEQ content in spring and winter was 77.5% and 73.2% higher than that in summer, respectively. From 2018–2019, the dry deposition flux of total-PCDD/Fs-WHO2005-TEQ was 316.3 and 460.5 pg WHO2005-TEQ m–2 month–1 in Shanghai and Nanjing, respectively, while in 2020, it was 272.5 and 368.4 pg WHO2005-TEQ m–2 month–1, respectively. The average dry deposition flux of total-PCDD/Fs-WHO2005-TEQ in spring and winter was 47.6% and 53.8% higher than that summer in Shanghai and Nanjing, respectively. The above results indicate that COVID-19 in 2020 had a positive effect on air quality improvement in PCDD/Fs. On average, more than 98.88% of the total PCDD/Fs-WHO2005-TEQ dry deposition flux was primarily contributed by the particle phase. This was attributed to the fact that dry deposition of particle phase PCDD/Fs was mainly due to gravitational settling accompanied by higher dry deposition velocities, while the gas phase PCDD/Fs were deposited mostly by diffusion at a lower dry deposition velocity. © The Author(s).
Highlights
PCDD/Fs are common persistent organic pollutants (POPs) in the environment
In Shanghai, the total PCDD/Fs-WHO2005-Toxic Equivalent Quantity (TEQ) concentration dropped from 0.0291 pg-WHO2005-TEQ m–3 from 2018–2019 to 0.0250 pg-WHO2005-TEQ m–3 in 2020, while in Nanjing, it dropped from 0.0423 pg-WHO2005TEQ m–3 to 0.0338 pg-WHO2005-TEQ m–3
The total-PCDD/Fs-WHO2005-TEQ concentrations were calculated based on the combination of the PCDD/Fs mass concentration and the toxicity equivalence factor (TEF) following the World Health Organization (WHO) guidelines
Summary
PCDD/Fs are common persistent organic pollutants (POPs) in the environment. The elimination of PCDD/Fs occurs mainly through migration, diffusion and deposition, which is closely related to the distribution of the gas-solid phase and temperature in the atmospheric environment. Particulate matter is a type of aerosol It refers to solid or liquid particles in the atmosphere and can be further classified according to its size (Ghosh et al, 2014). PM2.5 is known as a fine particulate that can directly enter the lungs It is used as the main pollutant index that characterizes the ambient air quality (Chow et al, 2015). Aerosols in cities are mainly emitted directly from human activities such as combustion and automobile exhaust (Kong et al, 2014). The concentration, gas-particle partitioning and PM2.5-bound content of totalPCDD/Fs-WHO2005-TEQ, PM2.5 concentrations, and dry deposition of total-PCDD/Fs-WHO2005-TEQ in two cities (Shanghai and Nanjing) in the south of China from 2018 to 2020 were investigated, compared and discussed
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