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 investigated. Petri dishes coated with thin wax films fortified with PCDD/Fs were exposed to sunlight and to mercury high pressure lamps. Detection of the remaining PCDD/Fs revealed a degradation behaviour following first order kinetics with two phases the first of which was quantified. At exposure to sunlight, the rate constants of the first phase ranged 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 photodegradation rates increased with the degree of chlorination of the homologues. PCDFs were slightly less stable than the PCDDs. Application of the results to an existing model of atmospheric deposition of aerial contminants demonstrated that photodegradation is an important process in the fate of PCDD/Fs on vegetation and in the use of vegetation as a tool for air monitoring of PCDD/Fs. (C) 1997 Elsevier Science Ltd.