Mono- to Octa-Chlorinated PCDD/Fs in Stack Gas from Typical Waste Incinerators and Their Implications on Emission

Mono- to octa-chlorinated dibenzo-<i>p</i>-dioxins and dibenzofurans (mono- to octa-CDD/Fs) were determined in 14 stack gas samples from two municipal solid waste incinerators and two medical waste incinerators. The total PCDD/F concentrations were 5.1–390 ng/Nm³, and the mono- to trichlorinated homologues contributed 53.2–94.5% of the total concentrations. The homologue profiles were dominated by the MoCDF, ranged from 1.51 to 113.1 ng/Nm³, and the proportion that each PCDF homologue group contributed to the total concentration decreased with increasing chlorination level. The toxic equivalent concentrations (I-TEQs) were 0.01–2.81 ng I-TEQ/Nm³, with 2,3,4,7,8-PeCDF being the biggest contributor, at 30.6–60.0%. Correlations were found among the PCDD/PCDF ratios (D/F ratios), the degree of chlorination, and the TEQ. Stack gases with low I-TEQs had higher proportions of the less chlorinated homologues and lower D/F ratios, which could be attributed to the removal of the more chlorinated isomers by the air pollution control systems used by the incinerators. 2,8-DiCDF, 2,4,8-TrCDF, DiCDF, and TrCDF can be used as TEQ indicators for monitoring PCDD/Fs. 2,8-DiCDF and 2,4,8-TrCDF correlated well with the TEQ because they strongly correlated with 2,3,4,7,8-PeCDF, implying possible correlations in their formation mechanisms