缓释螯合剂在铀污染土壤植物修复中的调控作用及机制

Efficient and safe remediation of uranium contaminated soil is one of important envionmental problems that need urgent resolution both home and abroad. During the process of phytoremediation of uranium contaminated soil, the improvement of desorption ability and the adjustment of release rate of uranium in contaminated soil will play an important role in phytoextraction of uranium from contaminated soils. In this work, based on modification of chitosan and β-cyclodextrin, a new kind of sustained release carrier named hydroxypropyl chitosan-grafted carboxymethyl β-cyclodextrin was prepared, and citric acid, oxalic acid,malic acid and lactic acid are used as sustained release targets. Sustained release chelant may improve the bioavailability of uranium in contaminated soil and adjust the release rate of uranium in contaminated soil, which was used as a new type chelant for phytoremediation of uranium contaminated soil. Sustained release behavior and kinitics law of uranium in contaminated soil were investigated, the release rates of uranium were effectively adjusted. The enhanced phytoremediation behavior of uranium contaminated soil with sustained release chelant was studied, the transportation, transformation and accumulation mechanisms on uranium in plants were explained, and the ecological risk assessment of sustained release chelant was also given during the process of phytoremediation. This research might provide scientific basis and technological support for the practical application of remediation of uranium contaminated soil.

铀污染土壤的高效、安全修复是国内外环境修复领域急需解决的重要环境问题之一。铀污染土壤植物修复过程中，有效提高污染土壤中铀的解吸能力的同时又能合理控制土壤中铀的释放速率，这对植物有效提取土壤中铀起到重要作用。本项目在壳聚糖和环糊精改性的基础上，获得一种基于羧甲基-β-环糊精接枝羟丙基壳聚糖的缓释载体，以螯合剂柠檬酸、草酸、苹果酸和乳酸为缓释对象，合成的缓释型螯合剂同时具备改善污染土壤中铀的生物有效性和调控污染土壤中铀的释放速率的特点，可成为铀污染土壤植物修复的新型螯合剂。研究缓释型螯合剂对污染土壤中铀的缓释行为、缓释动力学规律，有效调控铀的释放速率，研究缓释型螯合剂对铀污染土壤的植物增效修复行为，阐明缓释型螯合剂促进土壤-植物系统中铀的迁移、转化及积累的作用机制，评估缓释型螯合剂在植物修复过程的生态风险，此项研究可以为铀污染土壤修复的实际应用提供科学依据和技术支持。

随着核工业的迅速发展和核能的大规模开发，铀矿开采后留下的尾矿和废渣、铀的冶炼和浓缩过程不可避免地会向环境境中释放一定量的铀，导致周围土壤受到铀污染，铀污染土壤的高效、安全修复是国内外环境修复领域急需解决的重要环境问题之一。本项目在壳聚糖和环糊精改性的基础上，成功合成一种基于羧甲基-β-环糊精接枝羟丙基壳聚糖的缓释载体，以天然小分子有机酸柠檬酸作为缓释对象，在此基础上通过喷雾干燥法研究制备了新型缓释螯合剂，研究了缓释螯合剂中柠檬酸在水中的缓释动力学规律，研究了缓释型螯合剂对铀污染土壤中铀的缓释行为、缓释动力学规律，研究了缓释型螯合剂对铀污染土壤中铀的植物增效修复行为，阐明了缓释型螯合剂促进土壤-植物系统中铀的迁移、转化及积累的作用及机制，评估了缓释型螯合剂在植物修复过程的生态风险，结果表明:缓释螯合剂在增效植物修铀污染土壤的同时，又能有效降低植物修复过程中对地下水的渗滤风险。此项研究可以为矿区重金属污染土壤修复的实际应用提供科学依据和技术支持。