滨海潮滩土壤中微塑料污染下的抗生素多相分配与释放风险

Contaminations of antibiotics and microplastics simultaneously have been an emerging combined pollution in the coastal areas. Microplastics severed as vectors of chemicals and transported as well as diffused in the coastal environment and cause the potential ecological hazards eventually, which has been of concerned greatly. However, scientific problems are still to be resolved, such as the partitioning of antibiotics in the multiple components of the coastal soil environment polluted by microplastics and its relationship with the weathered surface characteristics of the microplastics, and the impacts on the bioaccessibility of the antibiotics. Therefore, the main objective of this research project is to determine the partition in the multiple components, chemical speciations and release risk of antibiotics in the soil-solution-microplastics system. In order to fulfill the objective, several methods and techniques are expected to be applied, which include soil-microplastics incubation spiked with 14C labelled antibiotics, dynamical soil solution sampling and in-situ measurement by diffusive gradients in thin-films technique (DGT), physiologically based extraction test (PBET) for the adsorbed antibiotics in the microplastics, simulation of surface weathering and coating with extracellular polymeric substance (EPS) produced from the formation of biofilm and modeling. The research results are expected to make clear of the characteristics of partitioning of antibiotics in the multiply components in the coastal soil polluted by microplastics and to establish a series of associated kinetic partitioning models. The mechanisms associated with the impacts of surface erosion, oxidation and coating of EPS on the adsorption and partitioning of antibiotics by solid phases are going to be revealed. The project will also estimate dynamic changes of the labile pool of the antibiotics in the soil-solution-microplastics system by DGT method and evaluate the risk of antibiotics releasing from the microplastics after ingestion of the microplastics by organisms. All the achievements of the research project are hopeful to be a scientific basis for the ecological risk assessment and management of the combined pollution with mciroplastics and antibiotics in the coastal zone.

抗生素与微塑料污染共存已成为沿海环境中新型的复合污染问题。微塑料作为化学污染物的载体在海岸带环境中迁移、扩散及其带来的生态风险正受到高度关注。但抗生素在潮滩土壤环境中受微塑料污染影响下的多相分配及其表面机制，以及对抗生素生物可给性的影响尚不明确。本项目拟通过土壤—微塑料混合培养、14C同位素示踪、土壤溶液动态取样与DGT原位测定、PBET提取、微塑料表面风化与胞外聚合物包覆模拟、模型分析等技术方法，研究抗生素在土壤—溶液—微塑料体系的多相分配、形态及释放风险等内容。阐明滨海潮滩土壤中微塑料污染情况下抗生素的多相分配特征，建立抗生素的动态分配预测模型；揭示自然条件下微塑料表面侵蚀、氧化以及胞外聚合物包覆等变化对抗生素吸附分配的影响机制；探明土壤中易解离态抗生素库动态变化及其控制因素，评估抗生素经微塑料进入生物体内的释放风险，为海岸带地区微塑料与抗生素复合污染的生态风险评估与管理提供科学依据。

抗生素与微塑料污染共存已成为沿海环境中新兴的复合污染问题。微塑料作为化学污染物的载体在海岸带环境中迁移、扩散及其带来的生态风险正受到高度关注。但抗生素在潮滩土壤环境中受微塑料污染影响下的多相分配及其表面机制，以及对抗生素生物可给性的影响尚不明确。本项目通过土壤—微塑料混合培养、土壤溶液动态取样与DGT原位测定、PBET提取、微塑料表面风化与生物膜鉴定分析、模型计算等技术方法，研究了抗生素在土壤—溶液—微塑料体系的多相分配、形态及释放风险等内容。取得了以下六个研究进展：（1）探明了典型潮滩土壤中颗粒类、发泡类、纤维类、碎片类和薄膜类等主要微塑料类型，并以聚苯乙烯发泡类微塑料和聚乙烯薄膜占主导， 300μm左右大小的微塑料居多；（2）发现了潮滩土壤微塑料的表面的多孔化、羰基指数、亲水性增强等特性，表面生物膜中以非活菌和胞外多聚物为主；（3）认识到聚氯乙烯（PVC）和聚乙烯（PE）微塑料可显著（p < 0.05）降低土壤中老化磺胺甲恶唑的解吸量，揭示了他们影响土壤吸附磺胺甲恶唑吸附差异化机制；（4）阐明了环境“老化”微塑料通过物理侵蚀、光照氧化和生物膜附着等途径改变其表面亲水性、增加表面微孔等效应增强对抗生素类污染物的结合能力，并改变吸附结合机制；（5）环境“老化”PE微塑料可显著增加土壤中磺胺甲恶唑从固相到生物体的再补给能力，但降低了磺胺嘧啶的再补给能力；（6）微塑料可降低土壤中磺胺甲恶唑的迁移速率，但不同添加量的微塑料其影响机制有明显差异，老化PP微塑料添加能显著（p < 0.05）降低土壤中磺胺甲恶唑在生物体内的释放。 研究成果为海岸带地区微塑料与抗生素复合污染的生态风险评估与管理可提供科学依据。