微塑料对四环素和三氯生在饱和多孔介质中迁移的影响

Effects of microplastics on transports of tetracycline and triclosan in saturated porous media

土壤和沉积物中的微塑料可能会影响污染物在环境介质中的迁移扩散。本研究以四环素和三氯生为对象,分析了二者在石英砂以及在添加了质量分数5%新制或老化聚丙烯微塑料的石英砂介质中的迁移动态。通过分析穿透曲线结合数学模型研究,结果表明,四环素和三氯生在不同pH条件下的迁移与它们的解离形态息息相关,四环素在中性条件下的迁移性较差,在酸性和碱性条件下受静电斥力影响迁移能力较强;三氯生在酸性条件下以分子形式存在时的迁移能力最弱,随着pH升高其迁移能力逐渐增强。介质中含有微塑料会抑制四环素和三氯生的迁移,使得动力学吸附点位数量增加,吸附速率减小,尤其是老化微塑料表面含氧官能团的产生较大地提升了非平衡吸附程度,使得延时因子增大,促进了四环素和三氯生在微塑料表面的吸附与截留。

Microplastics in soil and sediment may affect the transport of contaminants in the environment.In this study,we examined the transport behaviors of tetracycline and triclosan in saturated quartz sand with an addition of 5%newly made or aged polypropylene microplastics.The breakthrough curves were fitted with a convection⁃disper⁃sion model coupled with a two⁃site sorption(chemical nonequilibrium)model.The results showed that the transport dynamics of tetracycline and triclosan at different pH conditions were closely associated with their dissociation sta⁃tus.The transport of tetracycline was prohibited at neutral condition,but was almost unaffected at acid and alkaline conditions due to the electrical repulsion between tetracycline and porous media.Triclosan was least able to migrate in its molecular form under acidic conditions,but its transport ability was increased with increasing solution pH.The presence of microplastics in the media restrained the transport of tetracycline and triclosan by increasing kinet⁃ics sorption sites and reducing sorption rate.Particularly,the degree of nonequilibrium adsorption was promoted,and the retardation factor was increased when the aged microplastics existed in the porous media.As a conse⁃quence,the sorption and retention of tetracycline and triclosan were intensified due to the generation of oxygen functional groups in aged microplastics.