Formation of PCDDs, PCDFs, and coplanar PCBs from incineration of various woods in the presence of chlorides.

Exhaust gases from the combustion of woods (Japanese red pine, Japanese cedar, Siebold's beech, seawater-impregnated Japanese red pine and Japanese cedar, waste woods containing chlordane, and waste woods containing pentachlorophenol) were collected at the outlet of a combustion chamber. A small-scale incinerator with a stationary grate was used. The samples were analyzed for PCDDs, PCDFs, and coplanar PCBs by gas chromatography/ mass spectrometry (GC/MS). When the grate temperature of the combustion chamber was lower than 700 degrees C, the total amount of PCDDs, PCDFs, and coplanar PCBs formed was proportional to the chlorine content of the combustion samples. On the other hand, when the grate temperature of the combustion chamber was higher than 800 degrees C, there was only a slight formation of PCDDs, PCDFs, and coplanar PCBs regardless of the chlorine content of the combustion samples. When the grate temperature was low, nearly 90% of total PCDDs, PCDFs, and coplanar PCBs formed were PCDFs, whereas when the grate temperature was higher, 50-80% of total PCDDs, PCDFs, and coplanar PCBs formed was PCDFs. The total amount of PCDDs, PCDFs, and coplanar PCBs formed in a high-temperature condition was approximately 1/50 of that formed in a low-temperature condition. Coplanar PCBs tended to form less than PCDDs or PCDFs did. Mono-ortho-PCBs were formed several times more than nonortho-PCBs. PCDDs or PCDFs contributed significantly to the values of TEQ, while coplanar PCBs contributed only slightly.