SOIL-PLANT TRANSFER OF POLYCHLORINATED DIBENZO-P-DIOXINS AND DIBENZOFURANS TO VEGETABLES OF THE CUCUMBER FAMILY (CUCURBITACEAE)

In a preliminary study in fruits of zucchini (Cucurbita pepo L. convar. giromontiina) polychlorinated dibenzopdioxins and dibenzofurans (PCDD/PCDF) concentrations were found which were approximately 2 orders of magnitude higher than in other fruits and vegetables examined. These results formed the basis for field experiments on the uptake of PCDD/PCDF from contaminated soils by zucchini and related plant species (pumpkin and cucumber). The experimental design allowed the discrimination of several uptake pathways and an evaluation of their contribution to the total PCDD/PCDF contamination of the plants. Using two soils with different organic matter content, additional information was obtained on the influence of soil parameters on the soil-plant transfer of PCDD/PCDF. For zucchini and pumpkin (both belonging to the genus Cucurbita), root uptake of PCDD/PCDF and subsequent translocation to the shoots and into the fruits is the main contamination pathway. Cucumber plants (Cucumis sativus L.), by contrast, are mainly contaminated by deposition of airborne PCDD/PCDF and, consequently, show much lower PCDD/PCDF concentrations. The nature of the mechanism responsible for the unexpectedly high soil-plant transfer into plants of the species Cucurbita pepo L. remains to be clarified.