Phytoremediation of TNT -contaminated water by the submersed aquatic macrophyte Potamogeton pectinatus
Abstract
Phytoremediation using constructed wetlands has been identified as a potential cost effective method for the clean-up of 2,4,6-trinitrotoluene (TNT)-contaminated groundwater. The feasibility of employing sago pondweed (Potamogeton pectinatus L.) in wetland remediation systems was determined in growth chamber studies utilizing hydroponic plant cultures. The study objectives were to: identify the tolerance of sago pondweed to TNT; characterize and compare TNT dissipation from water in the presence and absence of this plant species; and examine plant uptake and fate of TNT. Results showed that sago pondweed could tolerate a one-time dose of 5 mg TNT L−1 without affecting plant growth, development, or physiological competence; however, multiple dosing at this concentration was toxic to the plant. When TNT was applied in successive doses (once every 4 days), sago pondweed could tolerate concentrations of only 0.5 mg TNT L −1. Concentrations as high as 60 mg TNT L−1 did not influence sago pondweed tuber germination; however, the growth of newly emerged plants from tubers was sensitive to concentrations ≥20 mg TNT L−1. In the presence of sago pondweed, TNT dissipation from water occurred at a faster rate than could be explained by photolysis. When incubated with plants, TNT concentrations decreased below HPLC detection limits within 48 to 96 hrs, whereas without plants, only 37 to 56% of the added TNT was lost a result of photolysis. As TNT concentrations decreased, mono- and di-aminonitrotoluenes increased in both the culture media and whole plant tissues suggesting a reduction reaction occurs as the first phase in TNT metabolism. The principle reduction product identified was 4-amino-2,6-dinitrotoluene. Plant uptake of TNT was not confirmed since reduction products were isolated inside and outside of plant tissues and the parent compound could not be detected in plant extracts. Evidence that sago pondweed released exudates into the surrounding aqueous media that could degrade TNT was demonstrated. Radiolabel studies revealed that mineralization of the parent compound did not occur in the presence of sago pondweed, but that TNT and its major photolytic product, 1,3,5-trinitrobenzene, were reduced to less toxic compounds.
Degree
Ph.D.
Advisors
Lembi, Purdue University.
Subject Area
Botany|Environmental science|Botany
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