Modeling sorption dynamics and ecotoxicological risk of microplastics and polybrominated diphenyl ethers in Arctic and subarctic freshwater.

Microplastics can act as sinks and carriers for hydrophobic organic contaminants, including polybrominated diphenyl ethers (PBDEs), increasing their bioavailability and potential harm to Arctic and subarctic freshwater biota. However, the sorption dynamics, drivers of co-contamination, and combined toxicity of microplastics and PBDEs remain poorly understood. This study develops a Bayesian Network (BN) to assess PBDE sorption onto microplastics and evaluate the ecotoxicological risk of PBDE-enriched microplastics with an application to northern pike in Great Slave Lake, Canada. The model integrates the physiochemical properties of PBDEs and microplastics, seasonal fluctuations, and local environmental factors to forecast their co-contamination and exposure to pike. Additionally, it incorporates fish physiological parameters to predict the cumulative ecotoxicological risk to pike. The results show that PBDE concentrations, seasonal changes, and microplastic abundance are the strongest contributors to reduced cell viability and endocrine-related effects in northern pike. By linking contaminant interactions, environmental drivers, and biological outcomes, this research improves ecotoxicological risk assessment for hydrophobic pollutants associated with microplastics in Arctic and subarctic freshwater ecosystems. The findings can support policymakers in designing targeted monitoring and mitigation strategies to protect the Arctic and subarctic region.