| The long-term dynamic changes of the degradation and bioavailability of pyrene as well as soil enzymatic activities were studied after addition of pyrene at the high rate (10mg-kg-1) and the very high rate (200mg-kg-1) to the riverine wetland soil in waterlogged and non-waterlogged conditions. After91days of incubation in room temperature, the residual rates of pyrene in waterlogged and non-waterlogged treatments at the very high rate of pyrene addition were61.1%and33.9%, respectively, while those in waterlogged and non-waterlogged treatments at the high rate of pyrene addition were79.0%and51.4%, respectively. Meanwhile, the bioavailable concentrations of pyrene extracted by Tenax-ta as the rapidly desorbed fraction of pyrene in waterlogged and non-waterlogged treatments at the very high rate of pyrene addition were20.31mg-kg-1and9.44mg-kg-1, respectively, while those in waterlogged and non-waterlogged treatments at the high rate of pyrene addition were1.01mg-kg-1and1.23mg-kg-1, respectively. The four parameter logistic model exactly (P<.0001) fitted the data of total and bioavailable pyrene contents. Additionally, the soil enzymatic activities of invertase, urease and polyphenoloxidase were sensitive to the concentration change of pyrene, whereas the soil catalase was not. Compared with non-sterilized treatment, sterilization of soil degradation of pyrene had a little margin, therefore, pyrene tolerance and degradation of the indigenous flora may exsit in soil.Two pyrene degration strains HLl and WN4were isolated from the riverine wetland soil of long-term artificial pollution (pyrene) in this study. The HLl belongs to Bacillus subtilis, and the WN4belongs to Ensifer adhaerens as analized by16S rDNA. The pyrene (50mg-L-1) degradation rate of strains HL1and WN4were46.64%and58.05%, respectively, after12days, while the pyrene degradation rate of mixed bacteria (WH) in12days was78.09%. The pyrene degradation of optimal incubation conditions were as follows:initial pyrene concentration at50mg-L-1, incubation temperature at30℃, and pH8. Co-metabolism experimental results showed that it had better pyrene metabolism for WH when salicylate, succinate and glucose were uased as substrates. The mixed flora WH from pyrene-contaminated soil was used for the study of soil pyrene bioremediation. The results showed that the amount of pyrene removed by the sterilized treatments were significantly lower than non-sterile handle. The residual rates of the sterilized treatments NS200s, S200s, NS10s and S10s were17.5%,26.5%,27.0%and10.5%lower than that of the the non-sterilized treatments NS200, S200, NS10, respectively, after the additon of WH. The degradation rates of straw added treatments (NSJ200s and SJ200s) were better than that of non-straw treatments (NS200s and S200s) at the very high concentrations (200mg-kg-1) level, but the degradation effect of straw treatments (NSJ10s and SJ10s) had no significant difference from non-straw treatments (NS10s and S10s) at the high concentration (10mg-kg-1) level.The results showed that the pyrene had not significantly changed the counts of bacteria and total microorganisms of the soil after90days of pyrene amendment while the number of actinomycetes and fungi reduced by one order of magnitude. The changes of bacterial and fungal community structure were obvious as analyzed by DGGE technique, which supported the results from microbial plate count.In conclusion, the present paper first discribed the accurate changes of pyrene degradation and bioavailability in soil by four parameters Logistic model, to the knowledge of us. The research provided academic understanding of the microbial biodegradation and ecotoxicity of hydrophobic organic pollutants like PAHs in soil. |
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