微生物修复石油污染土壤的生态毒性指示

摘要

发光菌的相对发光度和植物光合色素含量以及土壤酶活性是土壤石油污染程度和生态毒性强弱的综合反映。为探究不同生物指示方法对石油污染土壤生态毒性的指示效果以及污染土壤在生物修复过程中毒性的变化规律，采用前期筛选分离的三株对石油烃具有良好降解效果的降解菌构建混合菌体系，开展石油污染土壤模拟微生物修复实验。文章首先以明亮发光杆菌为指示生物考察不同修复时期土壤生态毒性，并以高等植物毒性试验以及土壤酶活性试验结果作为辅助证据从生态学角度揭示修复过程中石油污染土壤生态毒性的变化，并分析了以上3种指示方法的一致性。结果表明，该混合菌能高效降解对石油烃污染物，污染土壤经40 d修复后，石油烃污染物浓度从5000 mg·kg-1降到1781 mg·kg-1，去除率达到64%。高等植物生态毒性试验、土壤酶活性试验与发光菌生态毒性试验结果呈现良好的一致性，石油污染土壤的生态毒性随着微生物修复过程的进行呈先上升后下降的趋势。具体而言，修复初期的土样对小麦光合色素含量的抑制作用最大，叶绿素a含量相对于对照组降低了39.3%，仅为(1.36±0.04) mg·g-1；土壤过氧化氢酶酶活性与石油烃残留量呈极显著负相关关系（-0.973）；污染土壤生态毒性在修复的第8天达到最大，其二氯甲烷/二甲基亚砜浸提液中发光菌的相对发光度为18.1%，与0.187 mg·L-1 HgCl2的毒性相当。明亮发光杆菌的相对发光度和小麦光合色素含量以及土壤过氧化氢酶活性能较好地指示石油污染土壤在生物修复过程中的生态毒性，可作为石油污染土壤微生物修复效果的指示生物。%Bacterial luminescence, content of photosynthetic pigments together with soil enzyme activity could be used to comprehensively reflecting the soil health condition. In order to explore the soil ecotoxicity patterns and biological indicator effects, bioremediation of oil-contaminated soil were conducted. Oil degrading bacterial consortium were built with three strains isolated from oil-contaminated soil. Bacterial luminescence, chlorophyll a and carotene contents, and soil catalase activity was employed to evaluate the ecotoxicity of soil sampled in different bioremediation phases. Good consistency can be obtained among phytotoxicity tests, soil enzyme activity and Photobacterium phosphoreum ecotoxicity tests. The results showed that the application of a mixed bacterial consortium was illustrated to effectively remediate oil-contaminated soil due to the high TPH removal efficiency, which reduced the crude oil concentration from 5 000 mg·kg-1 soil to 1 781 mg·kg-1 in only 40 d. The maximum inhibition of bacterial luminescence for Photobacterium phosphoreum in the dichloromethane/dimethyl sulfoxide extracts was observed at the initial stage of bioremediation and gradually dropped to normal. Compared with the control group, the chlorophyll a content of Triticum acstivnm L. was significantly inhibited in the different phases of bioremediation. In soils S1, the chlorophyll a content decreased by 39.3%to (1.36±0.04) mg·g-1. A significant negative correlation can be found between soil catalase activity and the residue of petroleum hydrocarbon. The correlation coefficient is-0.973. Soil extract on the 8th day of the bioremediation remained constant at a relative luminosity of 18.1%, with toxicity equivalent to that of 0.187 mg·L-1 HgCl2. Therefore, bacterial luminescence, phytotoxicity (inhibition of chlorophyll a and carotene contents), and soil catalase activity could potentially be sensitive indicators to evaluate the effectiveness of bioremediation techniques.