Investigating the desorption of polybrominated diphenyl ethers from polyethylene microplastics to sediment

Microplastics (MPs), especially polyethylene (PE), are emerging contaminants with significant environmental impact and can act as vectors for toxic chemicals such as polybrominated diphenyl ethers (PBDEs). This study investigates the desorption behaviour of PBDEs from PE MPs to sediment, focusing on the influence of MP size, amount, and environmental temperature over a 60-day period. Using PE MPs derived from certified reference material ERM-EC590 and controlled experimental conditions, we found that smaller MPs (<1 mm) exhibited higher desorption ratios due to their larger surface area-to-volume ratios. Temperature exerted a marked effect on lower brominated PBDEs (BDEs-47, -99, and -100), with higher desorption ratios observed at 28 °C, but had minimal influence on highly brominated PBDEs (BDEs-183 and -209). Desorption ratios of BDE-47, BDE-100, and BDE-99 were higher at lower MP concentrations in sediment, but no such effect was observed for other, higher brominated congeners. These findings highlight the dynamic role of MPs as vectors of toxic organic pollutants in sediment, emphasising the complex interactions driven by both physico-chemical and environmental factors. This research enhances current understanding of contaminant behaviour at the microplastic-sediment interface.