Abstract
Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were analyzed in the pyrolysis products of the organochlorine pesticides chloronitrophene (CNP) and pentachlorophenol (PCP) to check the hypothesis that incineration of these pesticides, which contain comparatively high levels of dioxins as impurities, might be a major source of occasional high level of octachlorinated dibenzo-p-dioxin (OCDD) in the atmosphere. Analysis of all the isomers in the gaseous products as well as the residues clearly showed the production of high levels of dioxins by pyrolysis in air and in nitrogen. The highest levels of PCDDs, PCDFs, and PCBs were 1.1 × 108ng/g (under air, 800 °C), 5.1 × 105ng/g (under N2, 800 °C), and 6.8 × 103ng/g (under N2, 800 °C), respectively, in the case of PCP, and 3.8 × 105 (under air, 800 °C), 2.3 × 106ng/g (under air, 800 °C) and 9.0 × 104ng/g (under N2, 800 °C), respectively, in the case of CNP. It was estimated that 30-41% of the chlorine in PCP and 1.9-3.2 % of that in CNP were recovered in dioxins following pyrolysis.
The isomer profiles of PCDD/Fs and PCBs varied considerably depending on the experimental conditions and samples. The reasons for these large variations could not be clarified by the present study. Relatively high level of OCDD was detected in gaseous products from pyrolysis of PCP under all experimental conditions.
The isomer profiles of dioxins in the air samples of the present study could be differentiated from those from other sources. Their profiles were different from those in flue gases of ordinary incinerators when the relative concentrations of all isomers were compared.
