| In the present study, heavy ring PAH-degradation bacteria were screened from the soil contaminated with PAHs. And the composition changes of soil microorganism were investigated during the electro-bioremediation by PLFA and DGGE. Meanwhile, the degradation rates of PAHs were monitored based on the analysis of microbial community. All results could apply the degradation bacteria and the optimized conditions for electro-bioremediation of soil contaminated with PAHs. The conclusion of the study indicated as follows:(1)PAH-degrading bacteria were isolated from the soil contaminated with PAHs around Benxi iron and steel company using enrichment procedure, sublimation method and flask degradation experiment. The results showed that G1, G2 and G3 strains had stronger degradation ability of heavy PAHs. Meanwhile, the results of degradation ability was mixed bacteria>G1>G2>G3. G1, G2 and G3 strains were identified as Sphingomonas sp., Ochrobactrum sp. and Achromobacter sp. respectively based on their physiological characteristics and the sequence analysis of 16 S r RNA.(2)During the electro-bioremediation experiment, the high efficient degradation bacteria were inoculated was inculated in the soil polluted by PAHs. The structure changes of soil microorganism were analyzed under different electric field conditions(1.2 V·cm-1, 1.8 V·cm-1 and 3.6 V·cm-1) using the methods of PLFA and DGGE. The results are as follows:The species and amount of PLFA were determined in the different treatments. The results showed that soil microbial species and amount all changed after adding the high efficient degradation bacteria. Compared with the control CK, in the treatment with only adding the high efficient degradation bacteria, the microbial species and amount are reduced, but the amount of bacteria are increased, in which the amount of Gincreased and the change of G+ was little. Under the voltage of 1.2 V·cm-1, the total microbial amount increased by 9500 nmol·g-1 than that in CK, while the total microbial amount reduced 1807 nmol·g-1 and 6634 nmol·g-1 under the voltage of 1.8 V·cm-1 and 3.6 V·cm-1. Electric field also affected the amount of bacteria, actinomycetes and fungi. The result showed that the amount of bacteria reduced after increasing with the electic voltage increasing and the amount of actinomyces and fungi reduced all the time. Under the condition of the same voltage, the amount of fungus was higher in anode area than cathode area, but the amount of bacteria is the opposite; the amount of G-and G+ bacteria also indicated different responses in the electric field, G+ have no much change and the G- reduced as the voltage risesing.The change of three degradation bacteria G1, G2, G3 and the effect to native bacteria were analyzed in detail using the methods of DGGE. The results showed that contents of G1, G2 and G3 were obviously increased under 1.2 V·cm-1and 1.8 V·cm-1, but the contents of G1 and G3 were decreased and the content of G2 bacterial strain had little change under 3.6 V·cm-1. Indigenous bacteria diversity increased in the treatment CK′ and cathode region of the treatments 1.2 V·cm-1 and 1.8 V·cm-1, which proved that adding inoculating microbes was beneficial to the growth of indigenous bacteria under the optimal conditions.(3) It was indicated that there were correlation among soil p H, moisture, PAHs degradation rate, voltage and the quantity and diversity of microorganisms. The quantity and diversity of microorganisms had a significant negative correlation with voltage gradient and PAHs degradation rate and had a positive correlation with soil moisture and p H in the anode region. The quantity and diversity of microorganisms had a positive correlation with soil p H, moisture and PAHs degradation rate in the low voltage cathode region. The quantity and diversity of microorganisms had a negative correlation with voltage gradient, soil p H and moisture, and had a positive correlation with PAHs degradation rate in the high voltage cathode region. |
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