Polychlorinated dibenzo-p-dioxins and dibenzofurans in plywood combustion gas

Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/DF) levels in plywo od combustion gas were investigated for the effects of ammonium chloride (N H4Cl) and paint. For combustion systems in which neither NH4Cl nor paint we re present in the plywood samples, total amounts of PCDD/DFs in the combust ion gas were in the order of 35-529 ng/Nm(3), and were higher in the system s with softwood trees than broadleaf ones, depending on the Cl concentratio ns. For the systems with added NH4Cl and no paint, and those without NH4Cl but were painted, higher PCDD/DF rates were observed at combustion temperat ures of 270 degreesC and 500 degreesC, respectively. However, for the syste ms with both NH4Cl and paint, their amounts in the range of 0.6-13 ng/Nm3 w ere the lowest in all systems. The PCDD/DF abundance profiles were similar to their patterns in pentachlorophenol (PCP). Furthermore, it was found tha t the 2,3,7,8-chlorine substituted penta- and hexa-CDDs contributed more th an other 2,3,7,8-chlorine substitutes to toxicity equivalency (TEQ). (C) 20 01 Elsevier Science Ltd. All rights reserved.