溶解性有机质强化微生物降解多环芳烃的机制

Microbial degradation of polycyclic aromatic hydrocarbons (PAHs) can be enhanced through increasing the solubility of PAHs and providing the nutrients for microorganisms when adding the dissolved organic matter (DOM) to soils contaminated by PAHs. The recent studies focus on the effect of DOM on the solubility and degradation of PAHs. However, the mechanism of DOM enhancing the microbial degradation of PAHs is still not clear up to now. In this study, the sterilized DOM from cow manure, sludge, culture medium waste of mushroom or wheat straw is added to sterilized and non-sterilized soils contaminated by PAHs respectively. The solubilization effects of DOM on different forms and components of PAHs are revealed by measuring the dynamic changes of their content in sterilized soils. The characteristics of microbial utilization and degradation of DOM which serves as nutrient source of microorganisms are indicated by determing the composition, structure and property of DOM in non-sterilized soils at different culture time. The degradation of different forms and components of PAHs by soil microorganisms is revealed by analyzing the abundance and community structure of PAHs-degrading bacteria as well as degradative rates of different forms and components of PAHs in non-sterilized soils at different culture time. After the synthetic analysis of the above research contents is made, the mechanism of DOM enhancing the microbial degradation of PAHs through serving as the solubilizer for PAHs and nutrient source for microorganisms will be elucidated. This work is of important significance to enrich the theory of enhanced bioremediation and improve the treatment of PAHs-contaminated soils.

向多环芳烃（PAHs）污染土壤中添加溶解性有机质（DOM）能够通过增溶PAHs和提供营养促进微生物对PAHs的降解，当前研究主要关注DOM对PAHs的溶解和降解效果，关于DOM强化微生物降解PAHs的机制尚不清楚。本项目将灭菌后的牛粪、污泥、蘑菇培养基废料或小麦秸秆DOM分别添加到灭菌和非灭菌PAHs污染土壤中，测定灭菌土壤中不同形态、不同组分PAHs含量的动态变化，揭示DOM对PAHs的增溶作用；监测未灭菌土壤中DOM的组成和结构性质变化，探明DOM作为营养源被微生物利用和降解的特征；分析未灭菌土壤中PAHs降解菌的丰度和菌群结构以及不同形态、不同组分PAHs的降解率，确定微生物对PAHs的降解作用。综合以上三方面研究内容，阐明DOM作为PAHs增溶剂和微生物营养源强化微生物降解PAHs的机制，本研究对于丰富PAHs污染土壤的生物强化修复理论和促进PAHs污染土壤的治理具有重要意义。

本项目研究了PAHs降解基因pdo1、nah和C12O对焦化厂土壤中老化PAHs污染的响应，以及溶解性有机质（DOM）和用于提取DOM的农业废弃物对土壤中老化PAHs的降解和相应功能菌群的影响，证明了DOM能够通过增溶PAHs和为土著微生物提供营养从而促进PAHs降解菌丰度的增加和改变其群落结构，揭示了DOM强化土壤微生物降解老化PAHs的机制。主要结论如下：.（1）nah和 pdo1基因丰度可作为反映老化PAHs污染对土壤微生物影响的潜在生物学指标；.（2）分枝杆菌属（Mycobacterium ）、β-变形菌纲（Betaproteobacteria）和γ-变形菌纲（Gammaproteobacteria）细菌是老化PAHs污染土壤中重要的PAHs降解菌，并且分枝杆菌（Mycobacterium ）更为丰富；.（3）PAHs降解基因丰度与土壤TC、TN和DOC含量显著正相关，表明增加土壤中TC、TN和DOC的输入可能会通过促进PAHs降解菌增殖从而促进PAHs的降解；.（4）添加来源于农业废弃物的DOM能够通过增加PAHs降解菌的数量和改变它们的群落结构促进老化PAHs的降解，尤其是含有更高比例疏水性组分的DOM促进PAHs降解的效果更好；.（5）添加农业废弃物能够促进土壤中老化PAHs的去除，C:N 比例低的农业废弃物促进PAHs降解的效果更好；.（6）添加农业废弃物也能够通过增加PAHs降解菌的数量和改变它们的群落结构促进老化PAHs的降解，添加牛粪比添加小麦秸秆和蘑菇培养基废料对PAHs降解的效果更好，这可能与添加牛粪能够显著而持久地改变PAHs降解菌群落结构有关；.（7）添加农业废弃物来源的DOM比直接添加农业废弃物对于促进PAHs微生物降解的效果更为明显。