Preferential adsorption of Cd, Cs and Zn onto virgin polyethylene microplastic versus sediment particles

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 (Kd) 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