污泥胞外聚合物（EPS）对微塑料胶体稳定性及吸附四环素的影响机制研究

Microplastics have been identified as contaminants of emerging concern and research into their pollution problem has been sharply increasing in recent years. Microplastic can be released into the environment by various ways, and then enter into the municipal sewage treatment system. As the biological macromolecules that are ubiquitous in the sewage treatment system, extracellular polymeric substances (EPS) are secreted by the microorganisms, which have significant effects on regulating the stability and adsorptive property of inorganic colloid. These microplastics could be a new set of environmental concerns, because: (a) they are small enough to be taken up by biota and thus can accumulate in the food chain; and (b) they can sorb pollutants on their surfaces, thus increase risks of these particles. Therefore, the transport and transform as well as the adsorption ability to organic pollutant of microplastic will be affected by EPS. However, few studies have been conducted on the interaction between EPS and microplastic. In this proposal, EPS that extracted from active sludge, polystyrene, tetracycline were chose as the object of study. Some technologies such as dynamic light scattering, flow cytometry coupled with microscopy, high performance liquid chromatography will be used to investigate the adsorption and aggregation kinetics of microplastic, as well as the adsorption capacity changes of microplastic to organic pollutant in the presence of EPS. The purpose of all combination studies is to clarify the fate and transport of microplastic in the sewage treatment system, and provide the theoretical and technical support to pollution control of microplastic in the aquatic environment.

作为一种新型污染物，微塑料污染问题引起了广大学者的关注，其可通过多种途径排入环境，进入城市污水处理系统。污泥胞外聚合物（EPS）是污水处理系统中微生物生长代谢释放的一种大分子有机物质，可以调控环境中无机胶体的稳定性及吸附特性。大比表面积的疏水性微塑料被检出可吸附大量有机污染物，对水生生物及土壤生物造成很大威胁。因此，污水处理系统中，EPS对微塑料的迁移、转化及吸附有机污染物的特性将产生一定的影响。然而，有关EPS与微塑料相互作用的研究还鲜有报道。本课题以提取的活性污泥EPS、聚苯乙烯微塑料和四环素为研究对象，拟运用动态光散射、流式细胞仪结合显微术、高效液相色谱-质谱等现代仪器分析技术，在分子水平上研究EPS与微塑料颗粒相互作用的吸附、团聚动力学过程，以及EPS存在下微塑料对四环素吸附的影响，揭示微塑料在污水处理系统中的迁移和转化规律，为水体中微塑料污染控制提供理论及技术支撑。

作为一种新型污染物，微塑料污染问题引起了广大学者的关注，其可通过多种途径排入环境。细菌胞外聚合物（EPS）是环境系统中微生物生长代谢释放的一种大分子有机物质，可以调控环境中无机胶体的稳定性和吸附特性。基于此，本项目研究了细菌EPS在微塑料表面的吸附特性，发现细菌EPS在微塑料表面的等温吸附能较好地拟合Langmuir方程和Freundlich方程，EPS中含有的多糖成分能较多的吸附在聚苯乙烯微塑料表面，但是EPS中含有的蛋白质在微塑料表面的吸附力最强。通过动力学吸附实验及方程模型拟合，发现EPS在微塑料表面的吸附既包括单层吸附，又存在多层吸附；聚苯乙烯的絮凝实验研究发现，随着NaCl和CaCl2溶液浓度增加，聚苯乙烯微塑料的絮凝速率先增大后趋于平稳。聚苯乙烯微塑料在一价电解质溶液中的絮凝能力要弱于二价电解质溶液，EPS的加入会减弱微塑料的絮凝能力；微塑料对小油菜的胁迫实验研究中，发现不同尺寸微塑料胁迫均显著抑制小油菜生长发育和光合生理过程，其叶片数、株高、叶面积和生物量等表型指标以及叶绿素a、叶绿素b、叶绿素a+b、类胡萝卜素和光合特性等均随微塑料胁迫程度增加而显著降低。同时，微塑料胁迫显著增强了小油菜氧化应激反应能力，降低了小油菜叶片厚度、海绵组织厚度和栅栏组织厚度，提升了小油菜叶片植株冠层群体温度。研究结果将为揭示微塑料对生态环境健康影响提供理论基础。