Microplastics (MPs) in soil undergo different aging processes such as photoaging, mechanical abrasion and biodegradation, leading to alterations in the surface properties of MPs. In this study, we investigated the adsorption-desorption of chlorpyrifos (CPF) on pristine and UV light-aged low-density polyethylene (LDPE) and biodegradable (Bio) MPs that were derived from plastic mulch films. We also tested the bioconcentration of pristine and aged MPs (LDPE- and Bio-MPs aged under UV light and LDPE-MPs aged in three different soils) associated with CPF by earthworms (Lumbricus terrestris). The results showed that UV-aged MPs showed higher CPF adsorption capacities than pristine MPs, with the adsorption capacities at 184.9 ± 5.3, 200.5 ± 1.8, 193.0 ± 8.7, and 215.9 ± 1.1 μg g⁻¹ for pristine LDPE-, UV-aged LDPE-, pristine Bio- and UV-aged Bio-MPs, respectively. The desorption rate of CPF from UV-aged LDPE-MPs within 48 h was lower than the desorption from pristine ones (28.8 ± 7.7% vs. 40.0 ± 3.9%), while both pristine and UV-aged Bio-MPs showed very low CPF desorption rates. A 4-day Petri dish experiment showed that UV-aged MPs were significantly less concentrated in earthworm casts than pristine counterparts (52% and 36% lower for UV-aged LDPE- and Bio-MPs), while UV-aged MPs with adsorbed CPF were concentrated significantly more than UV-aged MPs without CPF. Interestingly, LDPE-MPs aged in soil with a high carbon, nitrogen, and carbon-to-nitrogen ratio were significantly more concentrated in earthworm casts than pristine LDPE-MPs. In conclusion, UV-aged MPs acted as stronger vectors for CPF than pristine MPs. The bioconcentration of MPs differed significantly due to microplastic aging, as well as the combined effect with CPF. Moreover, LDPE-MPs aged in soil with enriched carbon and nitrogen were significantly concentrated in earthworm casts. Further studies on the environmental behaviours of aged MPs associated with other pollutants in soil, especially soils high in carbon and nitrogen, are needed.

土壤中的微塑料 (MPs) 经历不同的老化过程，例如光老化、机械磨损和生物降解，导致 MPs 的表面特性发生变化。在这项研究中，我们研究了毒死蜱 (CPF) 在原始和紫外光老化低密度聚乙烯 (LDPE) 和源自塑料地膜的可生物降解 (Bio) MP 上的吸附-解吸。我们还测试了与蚯蚓 ( Lumbricus terrestris ) 的 CPF 相关的原始和老化 MP（在紫外线下老化的 LDPE 和生物 MP，以及在三种不同土壤中老化的 LDPE-MP）的生物浓度。结果表明，经过紫外老化的 MPs 表现出比原始 MPs 更高的 CPF 吸附能力，吸附能力分别为 184.9 ± 5.3、200.5 ± 1.8、193.0 ± 8.7 和 215.9 ± 1.1 μg g ⁻¹分别用于原始 LDPE、UV 老化 LDPE、原始 Bio 和 UV 老化 Bio-MP。48 小时内紫外线老化 LDPE-MPs 的 CPF 解吸率低于原始 LDPE-MPs 的解吸率（28.8 ± 7.7% 对 40.0 ± 3.9%），而原始和紫外线老化 Bio-MPs 的 CPF 都非常低解吸率。为期 4 天的培养皿实验表明，经过紫外线老化的 MPs 在蚯蚓模型中的浓度明显低于原始对应物（紫外线老化的 LDPE 和生物 MPs 分别低 52% 和 36%），而具有吸附 CPF 的紫外线老化 MPs比没有 CPF 的 UV 老化 MPs 更集中。有趣的是，在碳、氮和碳氮比较高的土壤中老化的 LDPE-MPs 在蚯蚓粪中的浓度明显高于原始 LDPE-MPs。总之，紫外线老化的 MPs 比原始 MPs 更能充当 CPF 的载体。由于微塑料老化以及与 CPF 的联合作用，MP 的生物浓度存在显着差异。此外，在富含碳和氮的土壤中老化的 LDPE-MPs 在蚯蚓粪中显着富集。需要进一步研究与土壤中其他污染物相关的老化 MP 的环境行为，尤其是高碳和高氮土壤。