Phytoextraction and Uptake Patterns of Weathered Polychlorinated Biphenyl-Contaminated Soils Using Three Perennial Weed Species

Three promising phytoextracting perennial weed species [Chrysanthemum leucanthemum L. (ox-eye daisy), Rumex crispus L. (curly dock), and Solidago canadensis L. (Canada goldenrod)] were planted in monoculture plots at two polychlorinated biphenyl (PCB)-contaminated sites in southern Ontario and followed over 2 yr to investigate the effects of plant age, contaminant characteristics, and species-specific properties on PCB uptake and accumulation patterns in plant tissues. Results from this study indicate that, for each of these weed species, shoot contaminant concentrations and total biomass are dependent on plant age and life cycle (vegetative and reproductive stages), which affects the total amount of PCBs phytoextracted on a per-plant basis. Even at suboptimal planting densities of 3 to 5 plants m(-2), all three weed species extracted a greater quantity of PCBs per unit area (4800-10,000 mu g m(-2)) than the known PCB-accumulator Cucurbita pepo L. ssp pepo (cv Howden pumpkins) (1500-2100 mu g m(-2)) at one of the two sites. Calculated PCB extractions based on theoretical optimal planting densities were significantly higher at both sites and illustrate the potential of these weeds for site remediation. This study also demonstrates that S. canadensis plants may accumulate PCBs along the stem length in a similar manner as C. pepo plants.