Emission Characteristics and Formation Pathways of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans from a Typical Pesticide Plant

Yufeng Ma,Xiaoqing Lin,Tong Chen,Jianhua Yan,Zhiliang Chen,Shuaixi Xu,Hailong Wu,Mingxiu Zhan,Xiaodong Li

doi:10.4209/aaqr.2019.04.0224

Abstract

ABSTRACT The emission characteristics and the formation pathways of the polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from a pesticide plant were well investigated. In the present study, the international toxic equivalent quantity (I-TEQ) value of the PCDD/Fs (0.087 ng I-TEQ Nm–3) in the flue gas at the outlet of stack can meet the emission limit (0.1 ng I-TEQ Nm–3). The I-TEQ value of the PCDD/Fs (3.25 pg I-TEQ g–1) in the fly ash is much lower than the permitted standard for disposal in sanitary landfill sites (3.0 ng of I-TEQ g–1). In addition, 1,2,3,4,6,7,8-HpCDD, OCDD and 1,2,3,4,6,7,8-HpCDF are the three main congeners in the PCDD/Fs for the outlet of both the secondary combustion chamber and the stack. 1,2,3,7,8-PeCDD, 1,2,3,6,7,8-HxCDD, 1,2,3,4,6,7,8-HpCDD and OCDD are the most dominant congeners for the PCDD/Fs from inlet of bag filter. PCDD/Fs may be formed through high temperature homogeneous synthesis and heterogeneous precursor synthesis in the flue gas. In addition, PCDD/Fs might be formed in bag filter via de novo synthesis. The main formation areas of PCDD/Fs are waste heat boiler and quenching/deacidification tower in this pesticide plant. The TEQ estimated emissions of PCDD/Fs reaches 9.3 g year–1. These findings are helpful for further controlling the formation and emission of PCDD/Fs in pesticide plants, yet more studies are still required.

Highlights

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as major classes of persistent organic pollutants (POPs), have become serious problem threatening environment and human health (Tsai et al, 2014; Hsieh et al, 2018b; Hung et al, 2018; Lee et al, 2018) because of their properties such as neurotoxicity, carcinogenicity, immunotoxicity, and bioaccumulation
The concentration and international toxic equivalent quantity (I-TEQ) value of PCDD/Fs at the outlet of the secondary combustion chamber (FG1) are 0.69 ng m–3 and 0.056 ng I-TEQ m–3, respectively, which shows that PCDD/Fs has been formed initially
The concentration and I-TEQ value of PCDD/Fs in the flue gas at the inlet of the baghouse filter (FG2) are 6.92 ng m–3 and 1.412 ng I-TEQ m–3, respectively, which shows that PCDD/Fs have been produced dramatically in the area

Summary

Introduction

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as major classes of persistent organic pollutants (POPs), have become serious problem threatening environment and human health (Tsai et al, 2014; Hsieh et al, 2018b; Hung et al, 2018; Lee et al, 2018) because of their properties such as neurotoxicity, carcinogenicity, immunotoxicity, and bioaccumulation. The emission characteristics of PCDD/Fs from industrial and thermal processes have been studied for over 40 years (Olie et al, 1977; Singh and Prakash, 2007; Mubeen et al, 2017), identifying several major sources of PCDD/Fs (McKay, 2002) such as municipal solid waste incinerators (MSWI) (Wei et al, 2016), cement kiln, the electric arc furnaces, and power plants (Tsai et al, 2014; Hsieh et al, 2018a; Xu et al, 2018; Zhan et al, 2018). The emission of each source is quite different because of the differences in scale, technology, air pollution control devices (APCDs), and the awareness of environmental protection.

Objectives

Methods

Results

Conclusion