抗生素在农田土壤颗粒态有机质中的分配与锁定机制

Soil contamination and associated risks by veterinary antibiotics has been concerned of greatly as a kind of emerging pollutants. However, limited information has been reported on the impact of soil constituents, especially the fractions of soil organic matter on the environmental fate of antibiotics in soil. This project is aiming at the severe pollution of veterinary antibiotics in soil of the farmland, in particular of the protected vegetable land as a result of long-term application of manure with large amount. Such a pollution is supposed to be connected with particulate organic matter(POM) which is a labile pool of organic carbon with a short turn over in soil and tending to be change with agricultural activities easily. The POM is expected to be isolated from the soil samples with different manures application, soil types and cultivation history. Advance technologies such as solid 13C NMR, 14C radioactive isotopic tracing, NICA-Donna model, etc. will be applied in the research. The research contains the following aspects including fractionation of the antibiotics in size-fractions of the POM, dissipation and degradation of POM associated antibiotics, sorption and sequestration of antibiotics by POM and its modeling. Significant results are expected to be achieved based on the project. First is the aggregate and particle fractionation mechanisms of the POM associated antibiotics and their extractable fractions. Second is dynamic changes of the POM associated antibiotics and the metabolites. Third is the surface microscopic mechanism and the predication model for antibiotics sorption and partition by the POM. All these results are assumed to be useful in the explaination of mechanisms of the antibiotics contamination in soils and the risk assessment of the polluted soils due to a long-term application of manure with large amount under modern agricultural environment.

土壤中抗生素等新型污染物的污染与风险问题日益引起关注，但目前土壤组分，尤其是有机质组分对土壤中抗生素环境行为的影响机制尚不清楚。本项目针对以设施菜地为主的农田土壤中长期大量施用有机肥导致土壤抗生素严重污染的现实问题，结合土壤颗粒态有机质（POM）这一受农业措施影响大、周转快的土壤有机碳库，采用从不同有机肥源、土壤类型和种植历史的农田土壤中分离提取的POM,通过固态13C核磁共振表征、14C放射性同位素示踪、NICA-Donna模型模拟等技术手段研究POM结合态抗生素的粒径分配、逸散降解、吸附锁定及其预测等内容。探明土壤POM结合态抗生素及其提取形态的颗粒分配机制，阐明POM结合态抗生素及其代谢产物的动态变化规律，揭示POM-抗生素结合的表面微观机制，建立土壤POM对抗生素的吸附分配预测模型，为现代农业环境下长期高量施用有机肥导致的土壤抗生素污染形成机制与风险评估提供理论依据。

土壤中抗生素污染问题已引起广泛关注，颗粒态有机质是土壤中重要的有机质组分，其组成与结构对抗生素的环境行为具有重要影响。本研究在文献调研基础上，优化了颗粒态有机质分离提取方法与富含颗粒态有机质土壤中抗生素分析方法，并探明了高量有机肥施用土壤中抗生素的污染特征及在土壤-水中的分配规律。针对分离到的土壤颗粒态有机质，利用稳定同位素质谱分析、13C固态核磁共振技术与同步辐射技术从物质组成、微观三维空间结构、微米及纳米尺度的表面结构官能团微域分布等方面系统深入分析了典型滨海湿地土壤、潮土和农田土壤中颗粒态有机质的物理和化学性质，认识到颗粒态有机质中存在游离型、团聚体内部结合型、有机-无机复合型等多种有机质形态特征，并且不同颗粒态有机质微域也存在表面结构官能团异质性等现象。. 通过室内模拟培养试验与同位素标记抗生素的田间降解试验相结合，研究了大量添加有机肥等颗粒态有机质条件下，抗生素的动态逸散和降解特征，计算提出了富含颗粒态有机质土壤环境中四环素、土霉素半衰期为17天的残留时间，并通过结合不同种植年限农田土壤中抗生素的积累分析，验证了模拟培养与田间试验条件下抗生素的动态逸散规律。在此基础上，为进一步分析土壤颗粒态有机质对抗生素的吸附与结合机制，利用不同性质特征的颗粒态有机质对土霉素、环丙沙星的吸附模拟试验等，阐明了土壤颗粒态有机质对土壤抗生素的吸附动力学和热力学特征，并采用同步辐射STXM、软x-射线NEXAFS和NanoSIMS等非破坏性表征技术，从纳米与分子尺度探明了颗粒态有机质表面存在脂肪基碳、酚基碳为主的亲水性吸附微域和以醌类、不饱和芳香碳等官能团为主的疏水性吸附微域的异质性。这些不同吸附微域的差异表现在不同性质抗生素在颗粒态有机质表面的吸附结合机制的差异上，如土霉素的吸附以表面吸附为主，受到氢键结合控制，而环丙沙星的吸附以共价结合或疏水作用为主。这些结果为解析土壤中抗生素的积累与迁移提供了理论基础。