Formation Pathways of Mono- to Octa-Chlorinated Dibenzo‑p‑dioxins and Dibenzofurans in Main Organochemical Industries

• Published in: Environmental science & technology Vol. 49; no. 18; pp. 10945 - 10950
• Main Authors: Han, Ying, Liu, Wenbin, Pan, Wenxiao, Wang, Pu, Tian, Zhenyu, Zhao, Yuyang, Wang, Mengjing, Chen, Xuebin, Liao, Xiao, Zheng, Minghui
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 15-09-2015
• Subjects: Benzofurans - chemical synthesis; Chemical plants; Dioxins; Halogenation; Industry; Molecules; Organic chemistry; PCB; Polychlorinated biphenyls; Polychlorinated Dibenzodioxins - analogs & derivatives; Polychlorinated Dibenzodioxins - chemical synthesis; Thermodynamics
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.5b02683

The concentrations and formation pathways of mono- to octa-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were investigated in main organochemical industries. High levels of PCDDs and PCDFs were detected. The total concentrations of 27 PCDD/F congeners in chloranil, 2,4-D, and 1,4-dichlorobenzene were 5302397 ± 8944449, 20963 ± 15908, and 242 ± 67 pg g–1, respectively, and the less-chlorinated PCDD/F levels were 12006 ± 20155, 9536 ± 5594, and 195 ± 94 pg g–1, respectively. The distribution trends of less and more chlorinated PCDD/Fs were similar in different chemical plants because of their similar formation pathways, which may also be related to the degree of chlorination of chemical products and purification processes. 1,2,3,4-TeCDF and 2,4,8-TrCDF were selected as model molecules to calculate the bond dissociation energy, showing that 2-MCDF, 3-MCDF, and 2,8-DCDF are more easily formatted as shown by the analytical results. The formation pathways of less to more chlorinated PCDFs are proposed to explain why 2-MoCDF, 2,8-DiCDF, 2,4,8-TrCDF, and 2,3,4,7,8-PeCDF are the dominant congeners and to explain why 2,3,4,7,8-PeCDF is the largest contributor of I-TEQs in most studies.