Differential bioavailability of field-weathered p,p′-DDE to plants of the Cucurbita and Cucumis genera

Field experiments were conducted to assess the bioavailability of weathered p,p′-DDE in soil to plants in the Cucurbita (squash, pumpkin) and Cucumis (cucumber, melon) genera. As expected, significant variability exists in the uptake of p,p′-DDE between plants of different genera. Root:soil concentration factors, defined as the ratio of p,p′-DDE (ng/g, dry weight) in the roots to that in the soil, approach 1.8 for cucumbers/melons and 16 for squash/pumpkin. However, significant differences were also observed among varieties of squash and pumpkin, with greater than an order of magnitude variation in the root:soil concentration factors and up to two orders of magnitude difference in the absolute amount of contaminant present within the plant. Although root systems routinely contain the highest concentration of p,p′-DDE (ng/g), this compartment comprises less than 2% of the total plant biomass. In all varieties but one, more than 86% of the extracted pollutant was in the shoot system. For two of varieties of Cucurbita pepo, concentrations of p,p′-DDE in the stems reached 1.1–2.2 mg/g and estimations of percent contaminant extraction from the soil ranged from 0.40% to 2.4%. These values approach those observed in the phytoremediation of heavy metals by “hyperaccumulating” species and indicate the potential for a plant-based remediation approach to soils contaminated with persistent organic pollutants.