Assessing Influence of Experimental Parameters on Formation of PCDD/F from Ash Derived from Fires of CCA-Treated Wood

Abstract

Ash residues from fires of radiata pine timber, both untreated and treated with chromated copper arsenate (CCA), were analyzed for the presence of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F). Fire conditions were simulated using a cone calorimeter. The sensitivity of the magnitude and profile of PCDD/F in the ash under controlled experimental conditions were examined to gain an insight into the formation of PCDD/F in a system containing CCA. The total amount of PCDD/F increased from 2.0 ng/kg of ash (0.05 ng of TE/kg of ash, using WHO-TEF) for untreated radiata pine to a maximum of 2700 ng/kg of ash (78 ng of TE/kg of ash) for 0.94% CCA. Ash containing CCA showed a distinct preference for formation of PCDFs, particularly the tetrachloro homologue. It is concluded that PCDD/F formation predominantly occurred via de novo synthesis during smoldering of the char rather than during the initial flaming and pyrolysis. Furthermore, the composition of the CCA constituents present in the timber was controlled to assess whether the physical presence of Cu, a known catalyst in PCDD/F production, was sufficient to account for the formation of PCDD/F in fires of timber impregnated with CCA.

Formation Of Dioxin During Smoldering Of Cca Treated Wood Char

“…These results were further confirmed in the burning of household refuse by Lemiuex et al [15]. Other recent studies have shown that, the presence of the preservative CCA in pine, dramatically increased the ash dioxin concentration in the ash under fire conditions [16]. The enhanced formation was observed during the burnout of the wood char, after cessation of the flames.…”

“…The chemical characteristics of the timber sample have been published elsewhere [16]. O 2 and N 2 (Linde) used in the annealing experiments were of 99.999% purity.…”

“…The method for preparing the char sample from the original wood has been described in detail elsewhere [16,19]. Briefly, as-received timber lengths were shredded and dried in an inert atmosphere.…”

“…An automated soxhlet unit (Buchi, Switzerland) was charged with a mixture of acetone:dichloromethane (50:50) to extract the analytes. Details of the subsequent preparation steps have been published previously [16]. Final analysis of the samples was conducted at the National Measurement Institute (NMI) -Pymble (Sydney, Australia).…”

Risks and Management of Dioxins and Dioxin-like Compounds in Baltic Sea Fish: An Integrated Assessment

“…In the Baltic Sea region, a TeCP-TCP-PeCP mixture is a notable PCDF source , Bergkvist et al 2005. Burning wood that also contains CCA salts greatly increases TEQ DF yields (Tame et al 2003b). Other biocides of importance for cumulative emissions include 2,4,5-T.…”