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Mechanisms of Pentachlorophenol Phytoremediation in SoilEPA Grant Number: U915148
Title: Mechanisms of Pentachlorophenol Phytoremediation in Soil
Investigators: Miller, Erica K.
Institution: Montana State University - Bozeman
EPA Project Officer: Smith, Bernice
Project Period: January 1, 1997 through January 1, 1999
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1997) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Biochemistry
The objective of this research project is to identify the mechanisms by which "Hycrest" crested wheatgrass (Agropyron desertorum x Agropyron cristatum) accelerates pentachlorophenol (PCP) degradation in soil. This research should furtherbroaden our understanding of how plants stimulate rhizosphere microorganisms to enhance the biodegradation of organic soil contaminants.
Ferro, et al. (1994) showed that "Hycrest" crested wheatgrass accelerates the degradation of PCP in soil compared to unplanted controls. Greenhouse studies were conducted using PCP-contaminated soil collected from a nearby site wasere planted with crested wheatgrass seed collected from a different PCP-contaminated site or with "Hycrest" crested wheatgrass. Our results confirmed that the unplanted control soil contained significantly more PCP than the two planted treatments after 13 weeks. In a second study, "Hycrest" seedlings were grown in sand either axenically or were inoculated with a bacterial consortium isolated from contaminated soil. The results showed that sterile wheatgrass seedlings could only tolerate 3 mg PCP per kg sand, while inoculated seedlings could tolerate 6 to 10 mg PCP per kg sand. Sealed flow-through systems were constructed to monitor 14C-PCP mineralization. Sterile "Hycrest" seedlings (~ 2 cm tall) are inoculated with an extract from PCP-contaminated soil (inoculated), with autoclaved soil extract (sterile inoculum), or with sterile extraction buffer (sterile), and are transplanted into sterile sand spiked with 0, 2, or 5 mg 14C-PCP per kg sand and placed in the sterile flow-through system. 14CO2 is trapped in 0.5 M NaOH and sampled every 7 days. Preliminary results show that sterile seedlings do not contribute to PCP mineralization, while inoculated seedlings and inoculated sand show significant levels of PCP mineralization. In most cases, the rate of mineralization by inoculated seedlings is higher than in inoculated sand, indicating that both plants and rhizosphere microorganisms are required for efficient PCP mineralization.