水环境中疏水性有机物与纳米塑料的相互作用机制

Microplastics and hydrophobic organic chemicals (HOCs) widely distribute in the global marine environment, the combined pollution they formed may affect the fate, transformation and bioavailability of HOCs. Previous study in our group found that the partitioning coefficients of polychlorinated biphenyls and polybrominated diphenyl ethers in the low density polyethylene and water phase were far lower than predicted values. The ratio of the partitioning amount of HOCs in the bulk plastic and that on plastic surface layer decreases with the decrease of plastic particle size, hence, it would be inaccurate to apply the partitioning coefficients obtained from micro-sized polyethylene film on small size microplastics (e.g., nanoplastics). In order to accurately measure the partitioning coefficients of HOCs in plastic particles and water phase, this project plans to use nanoplastics as the target plastic particles, which have large specific surface area. We designed reasonable experimental equipment and method to accurately measure the partitioning amount. Combining with kinetic curves, we are going to fit the partitioning coefficient when reach balance. Furthermore, from microscopic aspect, we would investigate the main factors that may affect the partitioning coefficients. We would also investigate the relationship between the partitioning coefficients and the hydrophobicity of HOCs, and further illustrate the partitioning mechanism of HOCs in nanoplastics. This project would provide reference data to future researches on predicting the amount of HOCs that carried by microplastics, provide technical support for future researches on the environmental behaviors and biological effects of the combined pollution of microplastics and HOCs. This project has important scientific significance as it would provide theoretical foundation for microplastic pollution control and treatment.

微塑料颗粒和疏水性有机物（HOCs）在全球海洋环境中广泛分布，二者形成的复合污染影响有机物在环境中的迁移转化及其生物可给性。课题组前期研究发现强疏水的多溴联苯醚和多氯联苯在低密度聚乙烯膜与水相之间的分配常数远小于预测值。有机物在塑料内部和塑料表层的分配比随塑料颗粒粒径的变小而变小，用大尺寸聚乙烯膜测得的分配常数应用到小粒径微塑料上极有可能是不准确的。为了更准确地测定HOCs在塑料颗粒与水相中的分配常数，本项目拟采用粒径极小的纳米塑料，合理设计实验装置和方法来更准确地测定其分配量，结合动力学曲线拟合平衡时的分配常数；从微观层面探索影响其分配常数的因素，探讨该分配常数与有机物疏水性的关联性，阐明HOCs在纳米塑料上的分配机制。为预测环境中微塑料颗粒上的疏水性有机物分配量提供参考，为微塑料和有机物的复合污染的环境行为和生物效应的研究提供技术支撑，为治理微塑料污染提供理论依据，具有重要科学意义。

近年来，塑料制品的大量使用与丢弃，导致大量废弃塑料在环境中不断累积，河流水体环境中的微塑料颗粒不断被检出。微塑料易吸附环境中的疏水性有机污染物，形成复合污染。本项目主要针对实际环境中的微塑料污染现状，研究微塑料与典型疏水性有机污染物的相互作用，特别是微塑料作为载体携带疏水性有机物进入海洋的入海通量。在水环境中采集到的所有微塑料颗粒中，和聚丙烯为主要的塑料类型，其他类型还包括聚苯乙烯、聚氯乙烯等等。珠江入海口水体中微塑料附着的多环芳烃、多溴联苯醚和多氯联苯的中值浓度分别为2010、412和67.7 ng/g，但这些有机污染物的浓度范围跨度较大，分别为25~40,100、0.84~14,800和1.86~456 ng/g。结合前期研究所得塑料河流通量数据，估算出珠江三角洲河流塑料附着的多环芳烃、多溴联苯醚和多氯联苯年入海通量为6.75、3.77和0.37千克。对比河流中的其它传输介质，塑料在有机污染物河流入海中的贡献量是无足轻重的。尽管如此，由于附着有机污染物的微塑料被生物吞食后易在生物体内富集，微塑料与有机污染物复合毒性的潜在生态风险仍不容忽视。本项目的研究为未来更进一步探究微塑料与有机物复合污染的生态效应提供重要数据支撑。