Plastic pollution has become a major environmental concern worldwide, and marine ecosystems have become polluted with ubiquitous microplastic particles (MP). MP can contain chemical additives and can also scavenge pollutants from the surrounding environment, and these co-contaminants may threaten the marine biota when MP become inadvertently ingested and transferred up the food chain. However, our understanding of the sorption-desorption kinetics of chemical compounds bound to MP remains limited. Moreover, whether MP are better transport vectors of co-contaminants than other natural particles (e.g. sediment) has not received much attention. Here, we used radiotracers to examine the partition coefficients (K_d) of three trace metals (¹⁰⁹Cd, ¹³⁴Cs, and ⁶⁵Zn) to virgin MP (32–75 μm polyethylene beads) and to natural sediment particles of a similar size (35–91 μm) in seawater. After 72 h, sediment particles adsorbed 2.5% of ¹⁰⁹Cd, 68.0% of ¹³⁴Cs, and 71.0% of ⁶⁵Zn, while MP adsorbed <0.8% of these three elements. Results highlight that under these experimental conditions, virgin polyethylene MP may not be effective transport vectors for these trace metals. Important variations in K_d were observed between elements, inciting for further studies to decipher how chemical characteristics, MP composition, and associated-biofilms, all interact in these biokinetic processes. These results demonstrate how radiotracers can allow us to address important knowledge gaps and broaden our understanding regarding the interactions between waterborne contaminants, naturally occurring particles and marine wildlife.

塑料污染已成为全球主要的环境问题，海洋生态系统已被普遍存在的微塑料颗粒（MP）污染。MP可能包含化学添加剂，还可以清除周围环境中的污染物，当MP意外摄入并沿食物链转移时，这些共污染物可能威胁海洋生物。但是，我们对与MP结合的化合物的吸附-解吸动力学的理解仍然有限。此外，MP是否比其他天然颗粒（例如沉淀物）更好地是共污染物的运输载体，这一点尚未引起广泛关注。在这里，我们使用放射性示踪剂检查了三种痕量金属（¹⁰⁹ Cd，¹³⁴）的分配系数（K _d）Cs和⁶⁵ Zn）到纯MP（32-75μm聚乙烯珠）和海水中相似大小（35-91μm）的天然沉积物颗粒。72小时后，沉积物颗粒吸附了¹⁰⁹ Cd的2.5％，¹³⁴ Cs的68.0％和⁶⁵ Zn的71.0％，而MP吸附了这三种元素的<0.8％。结果表明，在这些实验条件下，纯聚乙烯MP可能不是这些痕量金属的有效转运载体。K _d的重要变化在元素之间观察到了这一点，这促使人们进行进一步的研究，以了解化学特征，MP组成以及相关的生物膜在这些生物动力学过程中如何相互作用。这些结果证明了放射性示踪剂如何使我们能够解决重要的知识空白，并拓宽了我们对水污染物，天然颗粒和海洋野生生物之间相互作用的理解。