【作者】 聂明；

【导师】 李博；

【作者基本信息】 复旦大学 ， 生态学， 2010， 博士

【摘要】 随着工业的发展,石油已成为当前全球最大的环境污染源之一。面对日趋严重的土壤石油污染,寻求行之有效的修复途径成为迫在眉睫的生态环境治理问题。植物修复是利用植物与微生物的相互作用清除环境中的污染物,具有环境友好与成本低等优势,已成为一项具有广阔应用前景的治理石油污染技术。然而,石油污染对修复植物、微生物及其相互关系有强烈的负面影响,并导致土壤功能退化。本论文选择芦苇作为植物修复工具种,从生态系统角度探讨芦苇及其根围微生物对石油污染的响应,着眼于黄河三角洲石油污染对植物修复系统的影响以及生物适应性对于植物修复的重要性,研究了微生物群落在芦苇根围效应作用下对石油污染的响应,揭示了植物修复过程中芦苇与微生物的相互作用,探讨了石油污染对芦苇光合作用产物分配与周转的影响,揭示了石油污染下芦苇对氮的利用方式以及土壤氮转化过程,得出以下主要结论：(1)石油污染深刻影响着芦苇、根围微生物及其相互关系。石油污染对芦苇的个体大小、生物量以及光合作用效率存在显著的负面作用；土壤微生物群落结构与动态、菌根真菌侵染率、胞外酶活性以及微生物驱动的氮循环均受到石油污染不同程度的影响；在石油污染下芦苇在生长早期加强了与菌根真菌的互作,对于缓解生长阶段营养缺乏以及促进营养吸收有积极的作用。(2)芦苇通过其根围效应缓解了环境胁迫对微生物的影响,对于根围微生物群落具有保育作用。芦苇根围效应能够有效地缓解黄河三角洲的土地次生盐渍化,降低土壤盐度以及提高水份含量。芦苇根围土壤中各类型细菌数量显著高于裸地土壤,包括细菌总数、十六烷细菌、F2油细菌与多环芳香烃细菌。在芦苇根围效应下缓解了土地次生盐渍化对各细菌多度的控制作用。此外,在芦苇根围较裸地土壤具有高的细菌多样性。表明芦苇根围为细菌的生长与发育提供了合适的微环境。(3)芦苇的生长期是植物修复的关键阶段。在整个芦苇生长阶段,石油污染对芦苇多个性状有显著影响,在生长早期显得尤为明显,表明该时期的芦苇对石油污染的胁迫最为敏感。此外,在芦苇生长早期,表征细菌数量的rpoB基因以及石油烃降解微生物的关键基因alkB与tol的拷贝数具有较高多度,表明植物修复主要在该时期完成。另外,在芦苇生长早期,石油浓度对各基因的拷贝数影响最为强烈,表明芦苇和石油烃降解微生物的相互作用在该阶段较为强烈。(4)石油污染下芦苇增加了生物量向地下的分配。芦苇生物量的积累被石油污染显著地抑制,然而根冠比随着石油浓度的升高而显著地升高,表明在石油污染下芦苇增加了其生物量向根部的分配。此外,在土壤受到石油污染后,较高的13C分配百分率在芦苇地下系统中被检测到(包括根13C、土壤13C、微生物生物量13C以及土壤呼吸13C)。上述结果表明,石油污染下芦苇将增加光合作用固定碳向其根部的分配并以土壤呼吸形式被快速周转,具有增进植物与微生物协作的潜力。(5)芦苇具有通过增加吸收有机氮来缓解石油污染土壤中无机氮周转快、消耗大等不利条件的潜力。石油污染阻碍了芦苇吸收无机氮与有机氮,但芦苇增加了有机氮在总吸收氮中的比重。不同氮形式利用的变化可能反映出芦苇对石油污染的适应性,在受石油污染土壤中有机氮对于芦苇的生长可发挥更加重要的氮源作用。此外,石油污染不同程度地促进了土壤中各种氮的转化过程,潜在地影响土壤中氮的平衡、动态以及可利用性。由于石油污染土壤中具有较高的总固持与总硝化速率,从而可能减少芦苇可利用无机氮的数量。更多还原

【Abstract】 Petroleum has become one of the world’s largest sources of environmental pollution with industrial development. It is urgent to develpop effective techniques for remediation of petroleum pollution. Phytoremediation, an environmentally-friendly and cost-effective technology based on the removal of petroleum hydrocarbons from the polluted soil by plants and their associated microbes, is becoming an increasingly important field in environmental and ecological research. However, petroleum pollution has profound effects on plants, microbes, and their interactions. In this way, soil functions are degraded seriously under petroleum pollution. In this study, we used Phragmites australis as a phytoremediation species to examine the ecosystem-level responses of P. australis, microbes and their interactions to petroleum pollution, and emphasized the effects of petroleum pollution on the phytoremediation systems and the significance of biological adaptations toin phytoremediation in the Yellow River Delta. The aims of this thesis were to:1) examine the rhizosphere effects on microbial abundance and diversity in petroleum-polluted soils; 2) better understand plant-microbe interactions for phytoremediation of petroleum-polluted soil; 3) evaluate allocation and turnover of photosynthetically-fixed carbon as influenced by petroleum pollution; 4) analyze P. australis’s use of different nitrogen forms and soil nitrogen transformation in the polluted environments. The major findings are summarized as follow:(1) Petroleum pollution had profound effects on P. australis, microbes, and their interactions. Plant size, biomass, and potentially photosynthetic capability were negatively related to petroleum concentration. Soil bacterial community structure and dynamics, colonization of arbuscular mycorrhizal fungi (AMF), extracellular enzyme activity, and nitrogen transformation driven by microbes were subject to changes after soil was polluted by petroleum. Higher rate of AMF colonization was found in P. australis roots in polluted soils compared to those in unpolluted soils at early stage of vegetative growth, suggesting AMF might play an important role in reducing initial nutrient deficiency of the plant in petroleum-polluted soil.(2) P. australis through rhizosphere effects could alleviate soil stresses and positively influenced soil microbes. P. australis roots could alleviate the stresses from soil salinization in the Yellow River Delta, and rhizosphere soils were mainly characterized by lower salinity and higher water content. For bacterial abundance, the numbers of total bacteria and hydroscarbon degraders were significantly higher in rhizosphere soils than those in bulk soils. Soil salinization was not the major determinant of total bacterial abundance. In addition, rhizosphere soils had higher bacterial diversity in comparison to that of bulk soil. High abundance and diversity of total bacteria with more hydrocarbon degraders in plant rhizospheres would potentially improve the roles of bacteria in maintaining ecosystem functioning and remediating polluted soils in the degraded ecosystems.(3) Early plant vegetative growth was the key period for phytoremediation. Petroleum pollution resulted in reduced P. australis performances across the growth stages, especially during vegetative growth. P. australis would be highly susceptible to petroleum pollution in the stage of plant vegetative growth. Petroleum had significantly positive effects on the rpoB, alkB and tol genes at plant vegetative growth stage, and greater abundance of these two genes was also detected at plant vegetative growth stage. These results showed that the effectiveness of phytoremediation was plant-dependent, and that the interactions between P. australis and petroleum-degrading bacteria appeared to be relatively stronger at plant vegetative growth stage.(4) P. australis increased biomass allocation to roots. Plant biomass significantly decreased under petroleum pollution, but root/shoot ratio both in plant biomass and 13C increased with increasing petroleum concentration, suggesting that the plant could increase biomass allocation to roots in petroleum-polluted soil. Furthermore, assimilated 13C was found to be higher in soil, microbial biomass, and soil respiration after the soil is polluted by petroleum. These results suggested that C released from roots rapidly turns over by soil microbes under petroleum pollution. The increased allocation of plant biomass to its below-ground parts might be adaptive in petroleum-polluted soil.(5) Plant assimilation of both inorganic and organic N was low in petroleum-polluted soil, but the percentage of organic N in total plant assimilated N increased with petroleum concentration, suggesting organic N made a great contribution to plant N availability. In addition, petroleum pollution promoted gross N transformations to some extent, but larger increases in gross N immobilization and nitrification rates relative to the increases in gross N mineralization rate might reduce inorganic-N availability to the plant. Therefore, the increased importance of organic N in plant N assimilation might be of great significance for plants growing in petroleum-polluted soils. Our results provide insights into the effects of pollutants on soil available N to the plant, and suggest that plants might regulate N capture under petroleum pollution.更多还原