| Polycyclic Aromatic Hydrocarbons(PAHs), a kind of aromatic persistent organic compounds, is widely distributed in air, water, soil and sediment, which have a "three-induced effect(carcinogenic, teratogenic, mutagenic)" on human health and ecological environment. PAHs is one of the most important research fields of the environmental pollutants.The purification, separation and identification of PAHs-degrading strains in surface sediments, which collected from Yangtze River in Dadukou Chongqing steel company, were carried out. Taking sodium alginate and calcium chloride, were embedding carrier and cross-linking agent, to make immobilization particles of characteristics degrading-bacteria. The degradation characteristics of target compound PAHs by bacterial suspension and immobilized bacteria of two strains were studied, respectively, in phenanthrene and fluoranthene(Phe and Fluo, for short) spiked sediment-water system. The immobilized particles were also carried out in the paper. The experimental results could give basic data and theoretical support for PAHs pollution restoration research about sediment. The main research contents and conclusions are as follows:Above all, purification and identification analysis of the feature degrading bacteria: Two PAHs-degrading bacterias(named S1, S2) were obtained by enrichment culture, purificating and separating from sediment. The isolated strains could use phe and fluo as the sole carbon source and energy. Based on the observation of electron microscope and electronic scanning microscope, growth curve, serial physiological biochemical identification experiments, PCR amplification, 16 S r DNA sequence analysis and phylogenetic tree, and combined with NCBI information and relevant literature, S1 and S2 were identified as Sphingomonas pseudosanguinis strain J1-q and Klebsiella sp. J2-K. The accession Nombers of S1 and S2 were KP216807, KP216808, respectively.Then, degradation characteristics of bacterial suspension in PAHs spiked sedimentwater system: Selected weak pathogenic-S1 and pseudomonas-S3, which bought in China Center of Industrial Culture Collection(CICC), for degradation. Based on growth curve, expanding culture two preserved strains, determined Phe and Fluo residue concentration of different time sampling in degradation system, and explored the degradation of Phe and Fluo by two strains suspension in the experimental conditions. Transfered bacteria suspension(10% volume ratio) to Phe and Fluo spiked sediment-water system, reaction achieved stability after degradation 42 d, results show that the degradation rate of phe and fluo by S1 were 51.18% and 43.37%, while by S3 were 44.75% and 37.77%.In addition, degradation characteristics of immobilized bacteria in PAHs spiked sediment-water system: S1, S3 were Immobilized in calcium alginate gel beads to degradate Phe, Fluo in the spiked sediment-water system. Results showed that immobilized strains had higher degradation efficiency than bacteria suspension. More than 69.84% Phe and 60.22% Fluo were degraded by S1-immobilized and 56.89% Phe and 47.96% Fluo were degraded by S3-immobilized, after degradation 49 d. Immobilization strains were more efficiency than bacteria suspension. Combined the blank experimental, the results showed that the biodegradation of bioaugmentation is the main factor of PAHs degradation, and it is far more than volatilization, photolysis and adsorption, tec.Finally, research of the immobilized particles: At first, density, elasticity, compressive strength, adhesion, stability, mass transfer and immobilize rate of immobilized particles were measured to determine the method feasibility. By scanning electron microscope, we found that complex honeycomb, rich of gap, large specific surface area of inside particles could provide ample space for cell adhesion, increase adsorption capacity, accelerate the mass transfer rate and provide nutrition for cell timely. Amount of bacteria was considerable between the outer layer and center of inside- new made particles; the density and size of bacteria of outer layer significantly greater than center after domestication, indicated that the bacteria could absorb nutrients for normal metabolism and breeding. Sodium alginate and calcium chloride ensing rapid mass transferation, were good immobilize materials. With the domestication prolonged, bacteria density of center unchanged or even decreased, particle size was almost the same, the internal network structure became looser, even multiple spherical inclusion and keep Unicom.Bioremediation effect of PAHs is one of the key research ment in the field of environment. To our knowledge, there were few related research reports about Chongqing urban rivers. The regional characteristics of the paper were significantly. The result of the study has a certain theoretical significance for further discussion on PAHs contaminated sediment bioremediation and application research of immobilization. Moreover, this study provided scientific data support for the further research on PAHs migration, transformation, degradation mechanismthe in water-sediment system. The Project was supported by the National Natural Science Foundation of China. As countries “water ten” has been promulgated, the results of the study became more important practical significance for maintenance Three Gorges Reservoir Area Health and water environment safety. |
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