Acceleration of Nonylphenol and 4-tert-Octylphenol Degradation in Sediment by Phragmites australis and Associated Rhizosphere Bacteria
ABSTRACT We investigated biodegradation of technical nonylphenol (tNP) in Phragmites australis rhizosphere sediment by conducting degradation experiments using sediments spiked with tNP. Accelerated tNP removal was observed in P. australis rhizosphere sediment, whereas tNP persisted in unvegetated sediment without plants and in autoclaved sediment with sterile plants, suggesting that the accelerated tNP removal resulted largely from tNP biodegradation by rhizosphere bacteria. Three bacterial strains, Stenotrophomonas sp. strain IT-1 and Sphingobium spp. strains IT-4 and IT-5, isolated from the rhizosphere were capable of utilizing tNP and 4-tert-octylphenol as a sole carbon source via type II ipso-substitution. Oxygen from P. australis roots, by creating highly oxygenated conditions in the sediment, stimulated cell growth and the tNP-degrading activity of the three strains. Moreover, organic compounds from P. australis roots functioned as carbon and energy sources for two strains, IT-4 and IT-5, supporting cell growth and tNP-degrading activity. Thus, P. australis roots elevated the cell growth and tNP-degrading activity of the three bacterial strains, leading to accelerated tNP removal. These results demonstrate that rhizoremediation of tNP-contaminated sediments using P. australis can be an effective strategy.
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ABSTRACT: Comparative study on 4-tert-octylphenol degradation under UV (253.7 nm) and VUV (combined 253.7 nm and 184.9 nm) radiation in aqueous solution was performed in laboratory scale in this paper. Excitation light played the key role on 4-tert-octylphenol photodegradation. 93.5% 4-tert-Octylphenol was decomposed after 20-min VUV radiation while only 49.5% degradation efficiency was achieved after 4-tert-octylphenol received UV radiation for the same irradiation time. Other factors influencing 4-tert-octylphenol degradation efficiency included solution pH, initial concentration and natural water constituents. Initial 4-tert-octylphenol concentration and pH exhibited different influence pattern on 4-tert-octylphenol degradation under UV and VUV radiation. 4-tert-Octylphenol photodegradation products were discerned by HPLC and GC–MS. 4-tert-octylcatechol was recognized as predominant photoproducts under both UV and VUV radiation. Trace amount of phenol was also detected when 4-tert-octylphenol was subjected to VUV radiation. Degradation of 4-tert-octylphenol upon UV radiation was, therefore, predicted to be initiated by the photoejection of an electron from excited 4-tert-octylphenol, whereas 4-tert-octylphenol photolysis upon VUV radiation may also involve the direct CC bond cleavage from excited 4-tert-octylphenol. No matter the excitation light wavelength, photopolymization process was found to occur at high initial 4-tert-octylphenol concentration. Special attention should be paid to the photopolymerization phenomena during practical application of 4-tert-octylphenol photodegradation.Journal of Photochemistry and Photobiology A Chemistry 01/2013; 251(1):69-77. · 2.42 Impact Factor