Use of olive oil for soil extraction and ultraviolet degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans

This paper represents a successful laboratory-scale photolysis of soil-boun d tetra- to octachlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) i n olive oil. The irradiation source consisted of two blacklight lamps emitt ing light at a near-ultraviolet range. Samples used in the experiments incl uded pure 1,2,3,4,6,7,8-heptachlorodibenzo-furan, PCDD/F extract-made of a wood preservative (chlorophenol product Ky 5), and soil that was highly con taminated with PCDD/Fs. Degradation of 1,2,3,4,6,7,8-heptachlorodibenzofura n dissolved in olive oil proceeded rapidly with a first-order reaction half -life of 13 min. Irradiation of a sail sample resulted in an 84% reduction in PCDD/F toxicity equivalent (I-TEQ) in 17.5 h. A more complete degradatio n of soil-hound PCDD/Fs was achieved after extraction of the soil with oliv e oil. The oil:was effective in solubilizing PCDD/Fs. After one extraction at room temperature, only 9% of I-TEQ remained in soil. Irradiation of the resulting extract reduced toxicity of the extract by 99%, and even the high ly chlorinated congeners octa-chlorodibenzo-p-dioxin and octachlorodibenzof uran degraded easily (97 and 99% degradation, respectively). Photodegradati on byproducts found included diphenyl ether and small amounts of dechlorina tion products, which were mainly nontoxic PCDD/Fs. Degradation was probably mediated by light absorption of unsaturated fatty acids and phenolic compo unds in olive oil, leading to sensitized photolysis of PCDD/Fs.