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PCDD/F TEQ INDICATORS AND THEIR MECHANISTIC IMPLICATIONS
Citation:
Oh**, J E., A. Touati, B K. Gullett*, AND J. A. Mulholland. PCDD/F TEQ INDICATORS AND THEIR MECHANISTIC IMPLICATIONS. ENVIRONMENTAL SCIENCE AND TECHNOLOGY. American Chemical Society, Washington, DC, 38(17):4694-4700, (2004).
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Description:
Stack gas samples from two incinerator facilities with different operating conditions were investigated to find polychlorinated dibenzo-p-dioxin/furan (PCDD/F) toxic equivalent quantity (TEQ) indicators from amongst the 210 PCDD/F isomers. Similarities in isomer patterns were also examined to understand how formation mechanisms relate to operating conditions and facility types and to relate specific indicators with formation mechanisms. Some of the tri-CDD/F (8-30%) and tetra-CDF (18%) isomers, as well as most of the highly chlorinated (penta-CDF, hexa-, and hepta-CDD/F) isomers, showed potential to be used as strong (R2>0.7) common indicators in both incinerators, including most of the toxic equivalent factor (TEF) isomers. A common formation mechanism was found, especially for highly chlorinated DD/F, regardless of facility type and operating condition. This resulted in similar isomer distribution patterns, and was responsible for the percentage of potential indicator isomers within each homologue. Chlorination/dechlorination reactions comprised the dominant formation mechanism for PCDF whereas condensation reactions of phenolic precursors were responsible for PCDD formation. The chlorination/dechlorination mechanism was closely related with the TEF isomers, so many PCDF isomers were found to be strong TEQ indicators. Unlike highly chlorinated PCDD/F, lowly chlorinated PCDD/F mechanisms (especially, mono- and di-CDF) were sensitive to operating condition and facility type. Mixed formation mechanisms were observed, resulting in variation of the observed isomer distribution patterns and relatively low correlation of these isomers with PCDD/F TEQ values.
