土壤中邻苯二甲酸酯微生物降解的有机-矿质复合体界面作用机制

The residues and contamination of phthalate esters (PAEs) in soils have attracted widely attention in the world. The correct prediction of PAEs biodegradability would pave a better way for risk assessment and management of PAEs contaminated sites and environmental health. However, studies about the interrelationships between the PAEs biodegradability and its interface behaviors on clay organo-mineral complexes are scarce. In this project, a selection of typical PAEs will be used as the model pollutants to explore its interactions with the testing sorbents: natural soil samples, the clay organo-mineral fractions and the simulated organo-mineral complexes to elucidate the mechanisms involved. Based on the characterization of surface and structural properties of these sorbents, the interface behaviors of PAEs on them will be investigated. The correlation of the main characteristic parameters and sorption/desorption coefficients will be established. Specifically, researches will be focused on influencing of the organo-mineral complexes interface interactions affecting biodegradation of PAEs. Theoretical model will be established to describe the relationship between the biodegradability and the sorption/desorption of PAEs by the soils and clay organo-mineral complexes. The biodegradation efficiency of PAEs in different forms in soil will be researched. Moreover, the main factors of soil properties affecting on PAEs biodegradability will also be discussed to understand the mechanism involved contributing to the differences of PAEs biodegradation in agricultural soils. The results will provide scientific basis for the PAEs pollution control and the human health risk management.

邻苯二甲酸酯（PAEs）在土壤中的残留与污染已引起国内外广泛关注，正确预测其生物可降解性对于生态风险评估和农产品安全管理具有重要意义。目前就土壤中PAEs微生物降解与其在粘粒级有机-矿质复合体上界面行为的关系及机制还鲜见报道。本项目以自然土壤、粘粒级有机-矿质复合体及模拟有机-矿质复合体为吸附剂，在对其进行表面和结构特性表征的基础上，考察PAEs在各吸附剂上的界面行为，建立吸附剂的主要特征参数与吸附/解吸系数之间的相关关系；重点研究粘粒级有机-矿质复合体界面作用对土壤中PAEs微生物降解过程的影响，构建PAEs在土壤和粘粒级有机-矿质复合体中的生物可降解性与吸附/解吸系数间的理论模型，探讨土壤中不同形态PAEs的微生物降解性能，从而揭示影响PAEs微生物降解的主要因素，明确不同特性土壤中PAEs生物可降解性的差异机制。本研究有望为后续的PAEs污染控制技术和风险管理决策提供科学依据。

本项目从四个地区（东北长春（CC）、华北沧州（CZ）、西北银川（YC）和中南长沙（CS））采集农田土壤，分离出矿质态胡敏素和粘粒级有机-无机复合体，研究两种PAEs单体——邻苯二甲酸二乙酯（DEP）和邻苯二甲酸二丁酯（DBP）在各吸附剂上的吸附行为，并明确不同土壤中PAEs生物可降解性的差异机制。这些研究结论可以为完善PAEs的土壤环境行为奠定理论基础。.主要研究结论有如下几点：.（1）四个地区土壤样品的孔容和比表面积为东北地区最大，中南地区最小；不同组分的孔容和比表面积大小排序为：粘粒级有机-无机复合体>矿质态胡敏素>土壤。DEP和DBP在四个地区土壤上的吸附量排序为：CC>CS>CZ>YC；不同组分的吸附能力排序为：粘粒级有机-无机复合体>矿质态胡敏素>土壤；四个地区的样品对DBP和DEP均存在解吸滞后现象，有机质含量越高，粒径越小，比表面积越大，孔隙结构越丰富时，吸附能力越强，也更难解吸附。.（2）以吸附剂的理化性质参数为自变量，以吸附系数Kf为因变量，建立多参数线性回归模型，回归方程分别为：.K_f=1.026×孔容-0.016，其中R2=0.545，F=2.095，sig.=0.040；.K_f=0.901×孔容-0.002，其中R2=0.849，F=7.892，sig.=0.010。.（3）DBP在四个地区土壤中的降解速率依次为：CS＞CC≈CZ＞YC，DEP的降解速率依次为：CC＞CS＞CZ＞YC；可见PAEs在土壤中的降解速率与其吸附亲和力并没有明显相关性；结合在均相体系的生物降解实验可以得出，土壤有机质含量和 pH 值是影响 PAEs生物可降解性的主要因素。.（4）DOM影响PAEs生物降解的机制有：一方面DOM能够促进微生物的生长以及提高酶的活性。另一方面DOM与PAEs的结合导致了与微生物的隔离作用。基于本论文实验成果来看，DOM对PAEs 生物降解的增强机制主要是由于 DOM 刺激了微生物的生长并提高了降解酶活性。.（5）降解菌活菌体与失活菌体均能吸附DBP和DEP，且活菌体吸附量要大于失活菌体；红外光谱分析表明，细菌对PAEs的吸附主要是通过C-H的伸缩振动产生；添加表面活性剂能够改变细菌对PAEs的吸附，从而进一步影响细菌对PAEs的降解。