title: Photolysis of polychlorinated dibenzo-p-dioxins and dibenzofurans dissolved in vegetable oils: influence of oil quality.
abstract: Sunlight or ultraviolet light irradiation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the presence of vegetable oil offers a potential method for the cleanup of contaminated soil. In this study, the effects of different types of vegetable oils on the photochemical degradation of 1,2,3,4,6,7,8-heptachlorodibenzofuran and heptachlorodibenzo-p-dioxin (1,2,3,4,6,7,8-HpCDF/HpCDD) were investigated in the laboratory. Using a blacklight lamp as a source of ultraviolet light, 93-100% of 1,2,3,4,6,7,8-HpCDF degraded in 60 min in rapeseed oil, extra virgin olive oil and olive oil. Less degradation occurred in palm oil (59%), toluene (39%) and hexane (20%). The better degradation in vegetable oils in comparison with organic solvents was attributed to the photooxidation of lipids producing hydrogen for PCDD/F dechlorination. In addition to the hydrogen donor capacity, permeability of ultraviolet light was involved in the differences between vegetable oils. alpha-Tocopherol and chlorophyll did not influence the performance of oil at concentrations normally present in vegetable oils, whereas beta-carotene had an inhibitory effect on the degradation of 1,2,3,4,6,7,8-HpCDF. Up to 28% of the degradation products of 1,2,3,4,6,7,8-HpCDF were formed via the dechlorination pathway. Products included both toxic (2,3,7,8-chlorinated) and non-toxic PCDD/Fs, the toxic PCDD/Fs being more stable. Irradiation of 1,2,3,4,6,7,8-HpCDD yielded only non-toxic dechlorination products. Polychlorinated hydroxybiphenyls (OH-PCBs), polychlorinated dihydroxybiphenyls (DOH-PCBs) and polychlorinated hydroxydiphenylethers (OH-PCDEs) containing one to seven chlorine atoms were not detected in irradiated HpCDF/HpCDD samples.
authors.affiliation: National Public Health Institute, Department of Environmental Health, P.O. Box 95, FI-70701 Kuopio, Finland. pirjo.isosaari@ktl.fi
authors.forename: Pirjo
authors.initials: P
authors.lastname: Isosaari
authors.forename: Olli
authors.initials: O
authors.lastname: Laine
authors.forename: Tuula
authors.initials: T
authors.lastname: Tuhkanen
authors.forename: Terttu
authors.initials: T
authors.lastname: Vartiainen
mesh_terms: D001572:Benzofurans / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated; D004787:Environmental Pollution / Q000517:prevention & control; D010782:Photolysis; D010938:Plant Oils / Q000737:chemistry*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry*; D011786:Quality Control; D012989:Soil Pollutants / Q000032:analysis*; D012995:Solubility; D014466:Ultraviolet Rays
chemical_list: D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; D010938:Plant Oils; D000072317:Polychlorinated Dibenzodioxins; D012989:Soil Pollutants