FORMATION OF DIBENZODIOXINS AND DIBENZOFURANS IN THE PHOTOCHEMICAL TRANSFORMATION OF POLYCHLORINATED PHENOLS

It is shown that in the direct photolysis of polychlorinated phenols ( 2,4,5-TCP, PCP) in aqueous solution, under the action of salar light o r UV-radiation from artificial sources, polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF) are found among the products of trans formation. A mechanism is suggested of formation of these toxic compou nds via the intermediate formation of free radicals. In the oxidation of chlorophenols by singlet oxygen, free radicals are not formed. Addi tion of fulvic acids prevents formation of PCDD and PCDF in solar ligh t, possibly as a result of trapping of intermediate radicals.