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W.L. Rooney¹, Z. Chen², A.P. Schwab¹, M.K. Banks² and C. Wiltsie¹
¹Department of Agronomy and ²Department of Civil Engineering, Kansas State University, Manhattan, KS, 66506


Recent studies have shown that phytoremediation is an effective means of reducing organic toxic compounds, such as polynuclear aromatic hydrocarbons (PAHs). However, little is known about the effect of specific plant traits on phytoremediation potential. Our objectives are to evaluate the role of biological nitrogen fixation, fertilization and their interactions in alfalfa (Medicago Sativa L.) on the phytoremediation of pyrene and benzo(a)pyrene in soil.

Experimental design was a 2 x 2 factorial with 16 replications. Four replications were destructively sampled at 3, 6, 9 and 12 months. Alfalfa varieties (representing nitrogen fixation levels) and fertilization levels were the variables, and an unvegetated control was included. Alfalfa varieties "Saranac" and "Ineffective Saranac" were utilized in the study. The two varieties are genetically and phenotypically identical except for nitrogen fixing capability. Saranac is capable of nitrogen fixation while Ineffective Saranac is not. Two levels of supplemental N, 0 and 50 lbs/acre, were the second factor. Three seedlings were germinated in each pot of an agricultural soil contaminated with pyrene and benzo(a)pyrene at initial concentrations of 100 ppm and 50 ppm per kilogram soil, respectively. Degradation of pyrene and benzo(a)pyrene were monitored by destructive soil sampling at 3, 6, 9 and 12 months. Results (3 month) indicate that no significant difference exist between N-fixation level or fertilization level for pyrene and benzo(a)pyrene degradation. In addition, there is no difference between the unvegetated control and treatments. Early sampling indicates little difference between vegetated and unvegetated tests. It is expected that at 6, 9 and 12 month sampling times, significant differences between treatments will emerge.

Key words: phytoremediation, nitrogen fixation, fertilization, alfalfa, PAHs, hazardous wastes


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