有机酸对鼠李糖脂同步解吸复合污染土壤中有机物和重金属的影响及机制

Site contamination with both organics and heavy metals has becoming increasingly prominent in China, research of remediation technologies for these sites is therefore of great significance. Soil washing is one of the few techniques that can simultaneously treat both organics and heavy metals in soils. However, for the washing of soils with mixed pollutants, currently most investigated methods are based on a combination of two chemosynthetic washing agents, and the consequent environment risk can not be ignored. A novel and environment friendly washing system, which combines rhamnolipid biosurfactants with natural organic acids (OAs), is worthy to be noted. In the present project we choose benzene hexachloride (BHC) and lead (Pb) as the representative organics and heavy metals to explore the effects and mechanism of OAs on the simultaneously enhanced desorption of organics and heavy metals by rhamnolipid. We tend to investigate the effects of OAs on the morphology of rhamnolipid, and the capability of rhamnolipid to solubilize BHC and complex Pb. We give a deep insight to the enhanced dissolution of soil organic matter by OAs and adsorptive interplay between OAs and rhamnolipid. We further systematically study desorption behaviors of BHC and Pb with the co-existence of rhamnolipid and OAs, and various characterizations are conducted on soils before and after desorbing treatments to reveal the relative reactions and mechanisms in the complicated systems. The investigation is supposed to provide theoretical basis as well as technical support for the simultaneous washing of organics and heavy metals from soils by rhamnolipid-OAs comibination.

我国由有机物和重金属造成的场地复合污染问题日益突出，开展修复技术及相关研究十分必要。化学淋洗是少数能够同时治理土壤中有机物和重金属的技术之一。但目前针对复合污染土壤，通常研究的是两种化学合成类淋洗剂的组合，其环境风险不容忽视。新型环境友好型淋洗体系，即生物表面活性剂鼠李糖脂和天然有机酸组合值得关注。本项目选择六六六（BHC）和铅（Pb）为有机物和重金属代表，以揭示有机酸对鼠李糖脂解吸土壤中有机物和重金属的影响及机制为主要目标；在研究有机酸对鼠李糖脂形态、增溶BHC及配合Pb能力的影响，以及探索有机酸对土壤有机质溶解的促进及与鼠李糖脂在土壤上吸附交互作用的基础上，系统研究有机酸和鼠李糖脂共存时BHC和Pb的解吸行为，并对解吸处理前后土壤进行表征，阐明复杂体系中的相关作用机制。通过本项目研究，为鼠李糖脂-有机酸组合同步淋洗修复有机物-重金属复合污染土壤提供理论基础和技术支撑。

我国由有机物和重金属造成的场地复合污染问题日益突出，开展修复技术及相关研究十分必要。化学淋洗是少数能够同时治理土壤中有机物和重金属的技术之一。新型环境友好型淋洗体系，即生物表面活性剂鼠李糖脂和天然有机酸组合值得关注。本项目选取典型有机氯农药（OCPs）γ-六六六（林丹）为土壤有机污染物代表，Pb、Cd为重金属代表，系统研究了有机酸柠檬酸对鼠李糖脂同步解吸复合污染土壤中污染物的效果和机制。结果证实，鼠李糖脂-有机酸组合可用于有机-重金属复合污染土壤同步淋洗修复。本项目研究可为有机-复合污染土壤修复提供理论基础和技术支撑。.主要研究内容及结论如下：.（1）研究了有机酸及鼠李糖脂单独或复配体系中OCPs及Pb、Cd的增溶/配合作用。总体上柠檬酸浓度提高有助于鼠李糖脂的增溶，且对于γ-六六六和p,p’-DDT，柠檬酸加入促进了鼠李糖脂对两种OCPs的增溶，且增溶协同作用较为明显；但柠檬酸抑制了鼠李糖脂对α-六六六的增溶效果。pH值和盐度对鼠李糖脂及复配体系增溶都有显著影响。鼠李糖脂对Pb和Cd具有较强的吸附作用。柠檬酸加入明显增加促进了鼠李糖脂与Cd的配合，而对配合Pb的影响不明显。.（2）揭示了鼠李糖脂及柠檬酸在土壤-水溶液中的吸附行为及SOM的溶解行为。柠檬酸加入，抑制了低浓度鼠李糖脂（0-5000 mg/L）在土壤上的吸附而促进了高浓度鼠李糖脂（10000-20000 mg/L）的吸附。鼠李糖脂的加入促进了柠檬酸在土壤上的吸附，且随鼠李糖脂浓度提高而增强。洗脱剂的加入有助于土壤溶解性有机质的溶出，随柠檬酸及鼠李糖脂浓度的增加，土壤溶解性有机质的含量也随之增加。.（3）阐释了柠檬酸-鼠李糖脂复合同步解吸复合污染土壤中林丹和Pb、Cd的效果和机制。柠檬酸的加入显著促进了鼠李糖脂对土壤中林丹的解吸。组合药剂对土壤中Pb的解吸表现出联合作用；但组合药剂对土壤中Cd的去除效果与柠檬酸单独体系相当。当鼠李糖脂浓度为1%，柠檬酸浓度为0.1mol/L时，组合药剂对土壤中林丹、Cd和Pb的解吸率分别为85.4%，76.1%及28.1%。鼠李糖脂-柠檬酸体系对不同形态的Pb和Cd去除能力有差异，其中对可交换态重金属去除最为有效。土壤中镉主要以可交换态存在，铅主要以有机态和残渣态存在。鼠李糖脂-柠檬酸组合对铅去除的联合主要贡献在对有机态去除的联合作用上。