An effective method to assess the sorption dynamics of PCB radiotracers onto plastic and sediment microparticles

One important aspect of marine plastic pollution is that small particles are ubiquitously present in seawater and can transport a large variety of co-contaminants. The sorption-desorption kinetics of these co-contaminants sorbed to microplastics (MPs) are not fully understood, partially due to the lack of any standardised procedures between studies. The present work aims at describing a new and efficient method to investigate the sorption of co-contaminants onto different types of particles using proven radiotracer techniques. This work provides recommendations as well as a thorough description of the materials, conditions and procedures required to optimise the adsorption of polychlorinated biphenyl (PCB) onto particles. Details of the controlled experimental conditions, such as the volume of the container, the concentration of particles, and specifics of the radiotracer are provided. In addition, a thorough description of the novel filtration methodology specific to these radiotracer techniques is presented, for the first time in the literature. To validate the efficiency of the method, we examined the partition coefficients (Kd) of ¹⁴C-PCB#153 onto virgin MP (10-29 µm polyethylene beads) and onto natural sediment particles that are similarly sized (1-17.8 µm) in seawater. After 40 h, plastic particles adsorbed 25.7% of ¹⁴C-PCB#153 while sediment particles adsorbed 89.3% of the same compound. Results suggest that in this scenario, polyethylene MP particles may be less effective transport vectors of ¹⁴C-PCB#153 than natural sediment particles. • Details of experimental conditions, such as the volume of the container, and the concentration of particles and of radiotracer, were defined; • A thorough description of the filtration methodology specific to radiotracer techniques is presented; • Results highlight that virgin polyethylene MPs may be less effective transport vectors of ¹⁴C-PCB#153 than natural sediment particles.