In situ phytoextraction of polychlorinated biphenyl - (PCB)contaminated soil

Abstract

A pilot-scale field trial of phytoextraction of PCBs provides insight into the practical application of this technology, using the plant species Cucurbita pepo ssp pepo cv. Howden (pumpkin), Carex normalis (sedge), and Festuca arundinacea (tall fescue). This in situ trial took place at a historically contaminated field site, in soil contaminated with a mean concentration of 46 microg/g (range of 0.6 - 200 microg/g) total PCBs (Aroclor 1254/1260). Shoot bioaccumulation factors (where BAF(shoot)=[PCB(shoot)]/[PCB(soil)]) of up to 0.29 were achieved in sedge. Pumpkin plants produced shoot BAFs of only 0.15. However, PCB concentrations in pumpkin shoots decreased as the distance above the root increased, suggesting that higher overall pumpkin shoot BAFs might be achieved in shorter, more densely planted plants. A model for estimating the overall PCB concentration in large pumpkin shoots with minimal sampling is proposed. Examination of congener data supports the hypothesis that C. pepo ssp pepo plants exhibit a unique biological uptake mechanism that allows for the accumulation of a significant concentration of PCBs in plant shoots. Although this mechanism is not well understood, the co-eluting IUPAC congeners 93/95 and 105/127 appear to be preferentially mobilized. Presently, all three plant species exhibit potential as PCB phytoextractors, however further research is required to elucidate methods for optimizing this technology.