PHOTODEGRADATION OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS IN CUTICULAR WAXES OF LAUREL CHERRY (PRUNUS-LAUROCERASUS)

The photodegradation of 2,3,7,8-chlorosubstituted PCDD/Fs dissolved in cuticular wax from laurel cherry leaves (prunus laurocerasus) was inv estigated. Petri dishes coated with thin wax films fortified with PCDD /Fs were exposed to sunlight and to mercury high pressure lamps. Detec tion of the remaining PCDD/Fs revealed a degradation behaviour followi ng first order kinetics with two phases the first of which was quantif ied. At exposure to sunlight, the rate constants of the first phase ra nged from 3.5 10(-2) h(-1) for 2,3,7,8-TCDD to 2.2 10(-1) h(-1) for 1, 2,3,4,6,7,8-HpCDF and were similar at exposure to mercury lamps. The p hotodegradation rates increased with the degree of chlorination of the homologues. PCDFs were slightly less stable than the PCDDs. Applicati on of the results to an existing model of atmospheric deposition of ae rial contminants demonstrated that photodegradation is an important pr ocess in the fate of PCDD/Fs on vegetation and in the use of vegetatio n as a tool for air monitoring of PCDD/Fs. (C) 1997 Elsevier Science L td.