Freshwater Phenanthrene Removal by Three Emergent Wetland Plants

The use of floating wetlands has been receiving increased attention as a minimally invasive method for oil spill remediation, but the species of vegetation incorporated in floating wetlands may influence the success of oil degradation. Therefore, a freshwater microcosm experiment was conducted at the IISD Experimental Lakes Area, Canada to assess the potential of common wetland plants Typha sp., Carex utriculata, and C. lasiocarpa, to remove phenanthrene, a polycyclic aromatic hydrocarbon ubiquitously found at oil spill sites. Triplicate microcosms containing 3L of lake water were established with either Typha sp., Carex utriculata, or C. lasiocarpa and then treated with nominal concentration of 1 mg/L phenanthrene and monitored over 21 days. Two types of reference microcosms were also included: one set with the same plant allocations but not treated with phenanthrene and another with water only and no plants or phenanthrene. Phenanthrene declined by over 89.30% in all microcosms that received the compound, but the decline was more rapid in microcosms that included Typha sp. and C. lasiocarpa, than those with C. utriculate or no plants. Declining phenanthrene concentrations in microcosms without plants may have resulted from biofilm stimulation. Specific conductivity and pH were influenced by plant type but not phenanthrene, while dissolved oxygen was influenced by both. There was no influence of phenanthrene on plant growth rates or root biofilm bioactivity, measured by adenosine triphosphate or oxygen consumption. Results indicate there may be plant-specific factors influencing remediation success which should be explored in future research.