氟喹诺酮类抗生素在农田土壤中的界面行为及调控对策研究

Fluoroquinolone antibiotics are a kind of emerging pollutant with property of “pseudo- persistence”, which have widely been detected at high concentrations in soils. Their release has been causing severe soil pollution and toxic effect, and threatening the food safety along with human health through food chain. The pollution status and environmental behaviors of fluoroquinolone antibiotics have been attracting increasing research concerns from scientists in environmental sciences worldwide. However, the study centering onthe environmental fate of fluoroquinolone antibiotics is still far from enough, and the factors influencing the interfacial interactions between fluoroquinolone antibiotics and soil particles as well as the intrinsic mechanisms are not fully understood yet. By using the state-of-the-art instruments and integrated analysis method, this project is aiming to gain deeper insight into the interfacial interactions of fluoroquinolone antibiotics in crop soils at molecular level. Through the analysis of micro-scale interfacial sorption process of fluoroquinolone antibiotics in various soil components, interaction mechanisms between fluoroquinolone antibiotics with biochar and the biochar-dissolved organic matter complex, as well as the effect of biochar addition on sorption behaviors of fluoroquinolone antibiotics in soils, the interfacial behaviors and processes of fluoroquinolone antibiotics in soil medium will be clarified. Furthermore, the strategies for fluoroquinolone antibiotics pollution control in crop soils will be proposed in this work. The results of this work are of significance for better understanding of the bioavailability and toxic effect of fluoroquinolone antibiotics in soils. In addition, our findings will be helpful for prediction of the regional environmental behaviors and risk assessment of fluoroquinolone antibiotics once they are released into the crop soils, and make scientific foundation for environment management of these contaminants.

氟喹诺酮类抗生素是一类具有“假持久性”的新型污染物，在农田土壤中残留浓度较高，易造成严重污染、产生毒害效应、经由食物链威胁粮食安全与人类健康，其污染现状及环境行为已受到各界学者的广泛关注。然而，关于该类抗生素在土壤中的界面行为及其调控对策的研究仍不尽完善。本项目采用从简单体系到复杂体系的研究思路，借助现代光谱、能谱和显微技术，运用综合创新分析方法，从微观尺度上获得对土壤中此类抗生素的界面行为及调控策略的深入理解和认识。通过分析氟喹诺酮类抗生素在土壤各组分上的吸附过程，对比不同农田类型土壤有机质对其吸附行为的影响机制，探究生物炭及生物炭-溶解性有机质复合物与该类抗生素的相互作用机理，明晰生物炭对其固定作用，阐释氟喹诺酮类抗生素在土壤中界面行为的影响因素及内在机制，提出其污染控制的调控原理及策略。研究成果可为准确预测抗生素污染的区域环境过程提供基础数据、为环保部门制定污染控制措施提供科学依据。

本项目提取并分离了土壤有机质胡敏素各个组分，制备了以农业废弃物、畜禽粪便等物质为原料的生物炭与生物灰，并完成了了上述样品的理化属性与微观形貌特征的表征测试。本研究中的目标化合物包括了氟喹诺酮类类抗生素环丙沙星(CIP)、磺胺类抗生素磺胺甲嘧啶、多环芳烃菲、增塑剂邻苯二甲酸酯二乙酯(DEP)，结合丰富的表征结果与批量吸附实验数据，从微观尺度上探讨了胡敏素及其组分、生物炭与生物灰对目标污染物的吸附机理，分析了生物炭的原始材料、制备条件、热解温度对其自身的理化属性（化学组成、极性、孔隙度等）的影响，以及对吸附强度和吸附非线性程度的影响机制。.本研究使用不同的化学方法去除胡敏素样品中的各个组分，通过表征数据可得，各步骤有效地去除了相应目标组分，去除方法可在今后有关土壤有机质分析研究中继续使用。随着土壤矿物、含氧烷基碳、脂质、木质素类物质依次从原始胡敏素样品中去除，残留下来的样品呈现出了更大的比表面积与微孔体积，大量被占据的吸附点位得到释放，对抗生素吸附强度逐渐增大。研究中直接观察到从胡敏素中提取出脂质与木质素均对磺胺类抗生素的吸附由线性分配作用主导且吸附强度极弱，因此去除上述两种有机组分后，胡敏素对磺胺类抗生素的吸附强度提高，吸附非线性增强。.本项目在300℃、500℃和700℃热解温度下制备了以畜禽粪便、农业废弃物为原材料的第一批生物炭，在富氧不控温条件下制备了相应的生物灰（bioash）。毛豆秆与玉米秆生物灰样品对CIP的有机碳标化吸附系数Koc值分别是同类生物炭Koc值12.7~19.0倍。生物灰样品富含芳香碳基团，可与CIP分子中苯环结构产生π-π作用，促进对CIP的吸附。而畜禽粪便类生物炭，随着热解温度从300℃到500℃，样品所含极性官能团减少，猪粪与兔粪生物炭与CIP之间的氢键作用减弱，使其对CIP的吸附强度低于富含大量烷氧基团的原始畜禽粪便样品。通过调整制备条件，在严格厌氧氛围下，本研究分别在6个温度（300℃、400℃、500℃、600℃、700℃和800℃）制备了第二批比表面积更大、孔隙结构良好的生物炭，其中800℃生物炭比表面积均大于400m2/g，800℃花生壳生物炭的对DEP吸附能力最强。从扫描电镜图可得，800℃花生壳生物炭表面生成了大量微孔，丰富的孔隙结构为DEP吸附提供了更多结合位点，促进了DEP在800℃花生壳生物炭表面及微孔内部的吸附。