活性炭结合碳纳米管材料修复洞庭湖洲滩湿地有机氯农药污染的微观机理研究

Wetland in Dongting Lake has been contaminated with organochlorine pesticides (OCPs) in various degrees at different levels. It is an important method for in-situ immobilization/stabilization persistent organic pollutants in wetland remediation using carbonaceous materials such as activated carbon. However, the adsorption capacity of activated carbon toward organic pollutants should be improved. Furthermore, the interaction between carbonaceous materials and organic pollutants and their mechanism on micro-scale needs further investigation. Due to high specific surface area and controllable porous structure, carbon nanotube materials exhibit high adsorption ability toward OCPs. In this project, the combination of activated carbon and carbon nanotube materials was used for in-situ remediation of OCPs polluted wetland in Dongting Lake. The change of OCPs concentration in pore water, quiescent flux and aqueous equilibrium in Dongting wetland after remediation will be investigated. The aim of this project is to elucidate the interaction among OCPs, activated carbon and carbon nanotube materials and OCPs’ mass transfer among medias during the remediation process, to in-situ analyze and characterize the trace distribution of OCPs on the surface and in the hole of wetland soil, activated carbon and carbon nanotube materials, to disclose the mechanism of in-situ remediation for OCPs polluted wetland on the micro-scale level using in-situ characterization technologies including microprobe laser desorption/laser ionization mass spectrometry, fourier transform infrared microspectroscopy, scanning electron microscopy with wavelength dispersive X-ray spectroscopy. This project will provide theoretical basis for effective control and remediation OCPs pollution in wetland ecosystem.

洞庭湖洲滩湿地不同程度地受到有机氯农药污染。采用活性炭等碳质材料原位固定/稳定化有机污染物是修复湿地污染的一类重要方法。然而活性炭对有机物的吸附容量有待提高、活性炭在湿地修复过程中如何与有机污染物发生相互作用及其微观机理是什么需要进一步研究。碳纳米管材料由于高比表面积和可控孔隙结构，对有机氯农药具有很强的吸附性能。本项目拟采用活性炭结合碳纳米管材料原位修复洞庭湖湿地中有机氯农药污染，研究修复后有机氯农药在孔隙水、静态通量和平衡溶液中的浓度变化，探究修复过程中有机氯农药与湿地土壤、活性炭、碳纳米管材料等多介质发生的相互作用及质量转移，采用微探针激光脱附/激光离子化质谱技术、傅里叶变换红外光谱技术、扫描电镜和X射线光谱等技术，原位表征有机氯农药在湿地土壤颗粒、活性炭和碳纳米管材料的表面与孔隙中的痕量分布，从微观尺度阐明湿地修复的机理，为有效控制和修复湿地生态系统中有机氯农药污染提供理论依据。

洞庭湖湿地孕育着丰富的野生动植物资源和越冬候鸟栖息地。然而历史遗留的有机氯农药杀虫剂、菲以及新出现的抗生素等难降解有机污染物最终流入洞庭湖并沉积在湿地底泥中。这些难降解有机污染物不仅污染了洞庭湖区的水质和土壤，而且还污染了洞庭湖区的水生生物，从而导致洞庭湖湿地生物多样性减少和净化水质能力降低。本资助项目研究了堆肥产物、生物炭、活性炭结合碳纳米管材料原位修复洞庭湖湿地难降解有机物污染的效果及其内在机理。研究结果发现，单壁碳纳米管材料比多壁碳纳米管材料对洞庭湖底泥中六六六和滴滴涕污染的修复效果好。多壁碳纳米管材料的粒径越小，对洞庭湖底泥中六六六和滴滴涕的修复效果越好。活性炭的修复效果比多壁碳纳米管材料好，其主要原因是我们实验中所用的活性炭的比表面积（802 m2/g）远远大于多壁碳纳米管材料的比表面积（126 m2/g）。同时，研究结果还发现，跟生物炭相比，堆肥产物由于其较高的ECE，EC，SOM和大量微量元素，是吸附和降解有机污染物的优良修复材料和土壤改良剂。修复后底泥对测试植物种子的发芽率没有明显的影响，而根伸长量比植株鲜重对污染物浓度的变化更加敏感。含有0.5％（w/w）多壁碳纳米管材料的菲污染沉积物表现出最高的微生物活性和Shannon-Wiener多样性指数。添加高浓度的生物炭和堆肥产品提高了湿地土壤优势门菌类的相对丰度，包括变形菌门，芽孢菌门，酸杆菌门，厚壁菌门，放线菌门和弯曲菌门，但同时减少了拟杆菌门相对丰度。同时，本资助项目研究了堆叠型氧化石墨烯低压纳滤膜的制备和分离性能研究。研究结果发现，这些纳滤膜对染料的截留率都在96%以上。此外，本资助项目还研究了氧化石墨烯基复合纳米抗菌材料的灭菌效果及其机理。研究结果发现，掺杂了纳米银的石墨烯基海绵对E. coli和S. aureus的灭菌率可分别达99.86%和99.31%左右。而通过简单的浸润-挤压-干燥步骤，将其循环抗菌12次后，其灭菌率仍然能达到85%以上。