PM01 Phytoremediation and Risk Assessment
Exhibit Hall
8:00 AM - Monday
(PM007) Comparison of root-zone methanotrophic and heterotrophic populations at two phytoremediation sites contaminated with trichloroethylene.
Lindner, A. 1, Pacheco, A.1, 1 University of Florida, Gainesville, Florida, USA
ABSTRACT- While phytoremediation has become increasingly popular as a means of remediating contaminants from the subsurface, relatively little is understood concerning the roles that microorganisms in the root zone play in contaminant removal and the effect of plant exudates and contaminant concentration on this microenvironment. Two broad objectives of this work were 1) to assess differences in cell counts in the root zones of 3 different plant species, loblolly pine, poplar and willow, currently used in active remediation of trichloroethylene (TCE) at two Superfund sites -LaSalle, IL and Savannah River Site (SRS), SC- and 2) to determine the effect of monoterpene plant exudates (represented by a-pinene) on the TCE oxidation potential of representative Types I, II, and X methanotrophs as measured by oxygen uptake methods. Counts of heterotrophs and methanotrophs throughout the 120 cm rhizosphere soil profile at the SRS ranged from 106 to 109 and from 101 to 104 cells g-1 dry soil, respectively, while bacterial counts at LaSalle, although higher than observed at SRS, did not vary from the control or throughout the soil profile. Contaminant concentration, plant species, or clone type were not observed to impact cell counts, whereas the degree of soil moisture content was shown to inversely impact cell counts. However, enriched methanotrophic mixed cultures derived from zones of high TCE concentration showed lower methane oxidation potentials than those from zones of low TCE concentration. Synergistic effects of a-pinene on TCE oxidation potential were observed with Types I and X methanotrophs whereas the opposite effect was observed with Type II representative. Focus of future studies will assess the contaminant oxidation potential of rhizosphere samples at both sites (with monoterpene and non-monoterpene releasing plants) as a means of better predicting the ability of these abundant microorganisms to oxidize TCE.
Key words: methanotrophs, phytoremediation, trichloroethylene