Atmospheric Wet Deposition of PCDD/Fs in the Ambient Air

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

doi:10.4209/aaqr.210096

Abstract

ABSTRACT Wet deposition is an important mechanism for removing air pollutants from the atmosphere. The total PCDD/Fs-WHO2005-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-WHO2005-TEQ concentrations in the rain, the PM2.5-bound total PCDD/Fs-WHO2005-TEQ content, and the PM2.5 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 WHO2005-TEQ m–2 month–1, respectively, while in Tianjin, they were 35.30, 42.40, 13.37, and 14.77 pg WHO2005-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-WHO2005-TEQ in the rain, in Beijing, the average total PCDD/Fs-WHO2005-TEQ concentration in the rain in spring, summer, fall, and winter were 1.70, 0.39, 1.42, and 1.52 pg WHO2005-TEQ L–1, respectively, while those in Tianjin, were 1.73, 0.42, 1.35, and 1.88 pg WHO2005-TEQ L–1, respectively. The above results show that the total PCDD/Fs-WHO2005-TEQ concentrations in the rain are significantly lower in summer, which is mainly due to the fact that in summer, the total PCDD/Fs-WHO2005-TEQ concentrations in the air are lower, and the proportion of the gas phase is increased. When the total PCDD/Fs-WHO2005-TEQ concentrations in the air are washed away by a heavy rainfall, the PCDD/F concentrations are diluted.

Highlights

Persistent organic pollutants (POPs) have characteristics that include persistence, toxicity, and biological accumulation and have a great impact on air quality (Hao et al, 2021; Sari et al, 2021)
Studies show that the retarding fuel injection timing will lead to increased emissions, and the emissions of PCDD/Fs of heavy-duty diesel engines are different at different exhaust gas recirculation rates (Chen et al, 2019; Zhao et al, 2019)
Wet deposition is the removal of particles in the atmosphere by precipitation, where precipitation scavenging accounts for the majority of PCDD/Fs removed from the atmosphere through wet deposition (Huang et al, 2011)

Summary

Introduction

Persistent organic pollutants (POPs) have characteristics that include persistence, toxicity, and biological accumulation and have a great impact on air quality (Hao et al, 2021; Sari et al, 2021). As a sub-group of persistent organic pollutants, PCDD/Fs (polydibenzo-p-dioxins and polydibenzofurans) are high similar in terms of structure and properties (Schecter et al, 2006). The toxicity of PCDD/Fs is estimated using the toxicity equivalent (TEQ) of 17 biotoxic homologues. They have high chemical stability and are difficult to be degraded in the atmosphere, soil, and other environmental media (Lee et al, 2016). Studies show that the retarding fuel injection timing will lead to increased emissions, and the emissions of PCDD/Fs of heavy-duty diesel engines are different at different exhaust gas recirculation rates (Chen et al, 2019; Zhao et al, 2019)

Methods

Results

Conclusion