Atmospheric Wet Deposition of PCDD/Fs in the Ambient Air

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

《Aerosol and Air Quality Research》 21卷6期 (2021/06) Pp. 1-16

https://doi.org/10.4209/aaqr.210096

摘要

Wet deposition is an important mechanism for removing air pollutants from the atmosphere. The total PCDD/Fs-WHO_(2005)-TEQ wet deposition from 2018-2020 was investigated for Beijing and Tianjin City in this study. In addition, the gas-particle partitioning of wet deposition, the total PCDD/Fs-WHO_(2005)-TEQ concentrations in the rain, the PM_(2.5)-bound total PCDD/Fs-WHO_(2005)-TEQ content, and the PM_(2.5) concentration were also studied for Beijing and Tianjin City, respectively. Between 2018 to 2020, as a whole, the average seasonal variations in PCDD/F wet deposition fluxes in spring, summer, fall, and winter were 50.50, 41.47, 23.03 and 16.76 pg WHO_(2005)-TEQ m^(-2) month^(-1), respectively, while in Tianjin, they were 35.30, 42.40, 13.37, and 14.77 pg WHO_(2005)-TEQ m^(-2) month^(-1), respectively. Because the two cities have more rainfall in spring and summer than they do in fall and winter, rainfall has a significant influence on the wet deposition flux. In regard to PCDD/Fs-WHO_(2005)-TEQ in the rain, in Beijing, the average total PCDD/Fs-WHO_(2005)-TEQ concentration in the rain in spring, summer, fall, and winter were 1.70, 0.39, 1.42, and 1.52 pg WHO_(2005)-TEQ L^(-1), respectively, while those in Tianjin, were 1.73, 0.42, 1.35, and 1.88 pg WHO_(2005)-TEQ L^(-1), respectively. The above results show that the total PCDD/Fs-WHO_(2005)-TEQ concentrations in the rain are significantly lower in summer, which is mainly due to the fact that in summer, the total PCDD/Fs- WHO_(2005)-TEQ concentrations in the air are lower, and the proportion of the gas phase is increased. When the total PCDD/Fs-WHO_(2005)-TEQ concentrations in the air are washed away by a heavy rainfall, the PCDD/F concentrations are diluted.

關鍵字

PM_(2.5) ； Wet deposition ； PCDD/Fs ； Beijing ； Tianjin