Plastic litters in marine environment usually contain varied types and contents of additives that can significantly affect the photochemical aging and fragmentation process of microplastics (MPs). This study investigated the photo aging process of two common polypropylene (PP) food packaging materials (i.e., meal box and tea cup) in artificial seawater within 12 d of ultraviolet (UV) irradiation. Results revealed that the aging of both plastic materials were critically inhibited compared with pure PP, indicating that PP food packaging materials in natural seawater may share longer aging time than pure ones. GC-MS analysis revealed that antioxidant Irgafos 168 (tris (2,4-di-tert-butylphenyl) phosphite) was the dominant additive in these plastic materials. Photo reaction between Irgafos 168 and hydroperoxide species on the surface of MPs to prevent the formation of hydroxyl radical was the possible mechanism for the inhibiting effects. After antioxidant was exhausted, its photo degradation products could become the dominant contributor to influence the aging process of MPs. This is the first work exploring the role of antioxidant on the aging process of PP MPs in simulated ocean environment. The findings could be of great help for unraveling the effect of antioxidants on the aging-related environmental risk of hydrocarbon plastics in ocean environment.

海洋环境中的塑料垃圾通常包含各种类型和含量的添加剂，这些添加剂会显着影响微塑料（MPs）的光化学老化和破碎过程。这项研究调查了两种常见的聚丙烯（PP）食品包装材料（即餐盒和茶杯）在紫外线（紫外线）照射下12 d内的光老化过程。结果表明，与纯PP相比，两种塑料材料的老化都受到了明显的抑制，这表明天然海水中的PP食品包装材料可能比纯PP具有更长的老化时间。GC-MS分析表明，抗氧化剂Irgafos 168（亚磷酸三（2，4-二叔丁基苯基）酯）是这些塑料中的主要添加剂。Irgafos 168与MPs表面的氢过氧化物物质之间发生光反应以防止羟基自由基的形成是抑制作用的可能机制。抗氧化剂耗尽后，其光降解产物可能成为影响MPs老化过程的主要因素。这是探索抗氧化剂在模拟海洋环境中对PP MPs老化过程的作用的第一项工作。该发现可能有助于阐明抗氧化剂对海洋环境中碳氢化合物塑料老化相关的环境风险的影响。这是探索抗氧化剂在模拟海洋环境中对PP MPs老化过程的作用的第一项工作。该发现可能有助于阐明抗氧化剂对海洋环境中碳氢化合物塑料老化相关的环境风险的影响。这是探索抗氧化剂在模拟海洋环境中对PP MPs老化过程的作用的第一项工作。该发现可能有助于阐明抗氧化剂对海洋环境中碳氢化合物塑料老化相关的环境风险的影响。