Atmospheric Concentration, Particle-bound Content, and Dry Deposition of PCDD/Fs

Fanxuan Yu ； Kangping Cui ； Hwey-Lin Sheu ； Yen-Kung Hsieh ； Xueying Tian

《Aerosol and Air Quality Research》 21卷5期 (2021/05) Pp. 1-18

https://doi.org/10.4209/aaqr.210059

摘要

In this study, the atmospheric total-PCDD/Fs-WHO_(2005)-TEQ concentrations, gas-particle partitioning, PM_(2.5) concentration, PM_(2.5)-bound total PCDD/Fs-WHO_(2005)-TEQ content and dry deposition flux in Shanghai and Nanjing were investigated from 2018-2020. In Shanghai, the total PCDD/Fs-WHO_(2005)-TEQ concentration dropped from 0.0291 pg-WHO_(2005)-TEQ m^(-3) from 2018-2019 to 0.0250 pg-WHO_(2005)-TEQ m^(-3) in 2020, while in Nanjing, it dropped from 0.0423 pg-WHO_(2005)-TEQ m^(-3) to 0.0338 pg-WHO_(2005)-TEQ m^(-3). The average concentrations of PCDD/Fs-WHO_(2005)-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-WHO_(2005)-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 PM_(2.5)-bound total PCDD/Fs-WHO_(2005)-TEQ content was 0.342 and 0.493 ng-WHO_(2005)-TEQ g^(-1) in Shanghai and Nanjing, respectively, while in 2020, it was 0.312 and 0.489 ng-WHO_(2005)-TEQ g^(-1), respectively. In Shanghai and Nanjing, the average PM_(2.5)- bound total PCDD/Fs-WHO_(2005)-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-WHO_(2005)-TEQ was 316.3 and 460.5 pg WHO_(2005)-TEQ m^(-2) month^(-1) in Shanghai and Nanjing, respectively, while in 2020, it was 272.5 and 368.4 pg WHO_(2005)-TEQ m^(-2) month^(-1), respectively. The average dry deposition flux of total-PCDD/Fs-WHO_(2005)-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-WHO_(2005)-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.

關鍵字

PCDD/Fs ； PM_(2.5) ； Particle-bound ； Phase distribution ； Dry deposition