Type of Document Master's Thesis Author Begum, Sajida Author's Email Address email@example.com URN etd-0707103-121017 Title Field Validation of Bentazon Phytoremediation Degree Master of Science (M.S.) Department Environmental Studies Advisory Committee
Advisor Name Title Ralph Portier Committee Chair Ed Overton Committee Member Paul Templet Committee Member Keywords
Date of Defense 2003-06-30 Availability unrestricted AbstractPhytoremediation with black willow (Salix nigra) was conducted in 1996 by planting trees at a density of 2000 trees/hectare at BASF Corporation in a shallow groundwater plume containing low levels of bentazon. In this project, the roots, stems,and leaves of the black willow plants were extracted and analyzed to see if bentazon from the ground water was taken up by the plants. Different extraction procedures such as liquid-phase extraction and solid-phase extraction were compared. Final determination using different analytical techniques such as GC-MSD, GC-ECD, and HPLC with UV detection for the isolation and analysis of bentazon residues from the plant matrix were compared and the best clean-up and analytical procedure for its determination in plant samples was demonstrated.
On analysis using the LLE and GC-ECD method, bentazon concentrations in the plant samples collected over a one-year period did not show any discernible pattern. Residues of the pesticide were found in 15% of all the plant samples analyzed at the method detection limit of 0.27 mg/kg. The average bentazon concentration found in the samples was 0.48mg/kg with a range of 0.7mg/kg and 0.32mg/kg.
Comparison of the LLE method with the SPE method of sample extraction shows the advantages of the SPE method over LLE due to decrease in the extraction time, use of less quantity of organic solvents, better quality of final extracts, and better recoveries. The average recoveries for leaves using LLE and SPE procedures with GC-MSD were 39.1% and 49.9% respectively. Average recoveries for stems using LLE and SPE with GC-MSD were 56.3% and 63.9% respectively. Average recoveries for the LLE procedure for all the five sets of samples using GC-ECD were 51.7%, 58.1% and 59.6% respectively for leaves, stems, and roots matrices.
Comparison of the HPLC method with GC demonstrates that GC is a preferable method for analysis of bentazon from plant matrices due to its sensitivity, reliability and higher separation efficiency. Positive identification of bentazon was difficult with HPLC because of its insufficient sensitivity for trace analysis and its low separation efficiency resulting in coelution and broad peaks.
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