Microplastics (MPs) are a widely distributed pollutant and have been attracting global attention. The increasing abundance of MPs in marine environments has raised concern about their adverse effects on marine organisms and influence on the fate of contaminants in seawater. In this study, we investigated the effects of natural aging on the adsorption of di (2-ethylhexyl) phthalate (DEHP), one of the most widely used phthalic acid esters (PAEs), in two types of MPs (polyethylene and polystyrene). Biofilm was observed on the surface of MPs after 3-month exposure in seawater. Atomic force microscopy revealed there were significant physical changes in the MPs after aging. Aging in coastal seawater for 3 months significantly reduced the MPs’ surface roughness and adhesion, and increased the Young’s modulus at the same time. Adsorption isotherms of DEHP indicated that aged MPs had stronger binding capacity of the organic contaminant than pristine MPs. Our data shed some light on the biogeochemical role of MPs in marine environments.

微塑料（MPs）是一种分布广泛的污染物，已引起全球关注。海洋环境中越来越多的 MPs 引起了人们对它们对海洋生物的不利影响以及对海水中污染物命运的影响的关注。在这项研究中，我们研究了自然老化对邻苯二甲酸二（2-乙基己基）酯（DEHP）（一种最广泛使用的邻苯二甲酸酯（PAE）之一）在两种 MP（聚乙烯和聚苯乙烯）中吸附的影响。在海水中暴露 3 个月后，在 MPs 表面观察到生物膜。原子力显微镜显示，老化后的 MPs 发生了显着的物理变化。在沿海海水中老化 3 个月显着降低了 MPs 的表面粗糙度和附着力，同时增加了杨氏模量。DEHP的吸附等温线表明老化的MPs比原始MPs具有更强的有机污染物结合能力。我们的数据揭示了 MPs 在海洋环境中的生物地球化学作用。