Microplastics (MPs), polymer particles capable of accumulating heavy metals from ambient medias, have been widely found in agriculture and pasture soils. Through the consumption of MPs in soils, heavy metals adsorbed on MPs can be transported into ruminant digestive guts. To explore the behavior of Cd loaded MPs in ruminant digestive system, we initially established a ruminant digestive in-vitro method (RDM) that simulates the rumination cycle between mouth and rumen to evaluate the release rates of Cd on 4 most commonly used undegradable MPs (PE, PP, PVC, and PS) and a biodegradable MP (PLA). After 120 h of adsorption, the Cd adsorption capabilities by 5 MPs ranged from 0.23 μg/g to 2.45 μg/g. Through RDM, all tested Cd loaded MPs released high proportions of Cd with release rates from 21.5% to 41.8%, where PLA showed the highest Cd release rate. Cadmium was mainly released in rumen and abomasum phases, and the rumination cycle between mouth and rumen can affect the Cd release from MPs. The present study provides a new view on the environmental hazard of heavy metal and MP pollution that their co-exposure to ruminants should be taken into account.

微塑料 (MPs) 是一种能够从环境介质中积累重金属的聚合物颗粒，已广泛存在于农业和牧场土壤中。通过消耗土壤中的 MPs，吸附在 MPs 上的重金属可以被运输到反刍动物的消化道中。为了探索 Cd 负载 MPs 在反刍动物消化系统中的行为，我们初步建立了反刍动物体外消化系统方法 (RDM) 模拟口腔和瘤胃之间的反刍循环，以评估 Cd 在 4 种最常用的不可降解 MP（PE、PP、PVC 和 PS）和可生物降解 MP (PLA) 上的释放率。吸附 120 小时后，5 MPs 的 Cd 吸附能力范围为 0.23 μg/g 至 2.45 μg/g。通过 RDM，所有测试的 Cd 负载 MPs 释放高比例的 Cd，释放率从 21.5% 到 41.8%，其中 PLA 显示出最高的 Cd 释放率。镉主要在瘤胃和皱胃阶段释放，口和瘤胃之间的反刍周期会影响MPs的Cd释放。本研究为重金属和MP污染的环境危害提供了新的观点，应考虑它们与反刍动物的共同暴露。