Phytoremediation of Anthracene Contaminated Soils by Different Plant Species

Phytoremediation is perceived as an alternative technology for contaminated site remediation. Yet, the mechanisms plants use to remove organic contaminants have not been fully elucidated. The objective of the current study was, therefore, undertaken to clarify the contribution of plants to the disappearance of organic contaminants in soil. Four plant species, including alfalfa, tall fescue, barley, and orchard grass, were examined for the ability to facilitate the degradation of the polyhydric aromatic hydrocarbon, anthracene. Soil samples were intermittently collected for two months to measure the disappearance of anthracene and bacterial number by GC and epifluorescence microscopy, respectively. Plant exudates were collected to determine their ability to solubilize anthracene. Alfalfa showed a 28％ enhancement in the disappearance of anthracene compared to the unplanted control. Root exudates from alfalfa increased the release of soluble anthracene by 25 to 80％ compared to the other species and unplanted controls. Among the plants tested, there was a positive correlation between enhancing the disappearance of anthracene by plants grown in soil and increasing the release of anthracene by isolated plant exudates. The results suggest that root exudates facilitate the mobilization of anthracene from soil and that the successful implementation of phytoremediation depends on the plant species. Further, root exudates may be a useful tool in screening plants for possible application in anthracene remediation.