Sorption behaviors of phenanthrene on the microplastics identified in a mariculture farm in Xiangshan Bay, southeastern China.

Recently, with the accumulation of evidence that microplastic can be ingested by a variety of marine organisms, microplastic sorption behaviors towards organic contaminants (OCs) have become the subject of more studies due to the concerns about the contaminant vector effect. In this study, the priority microplastics identified in a mariculture farm in Xiangshan Bay, China, including polyethylene (PE) and nylon fibers (i.e., derived from new fishing ropes and nets), were examined for their sorption behaviors. The results indicate that both plastic fibers show linear isotherms towards phenanthrene, a common target hydrophobic organic contaminant (HOC), revealing the characteristics of a partitioning mechanism. The sorption capacity of PE fiber was found to be 1-2 orders of magnitude higher (evaluated by Freundlich parameter log KF ) than that of nylon fiber, suggesting the importance of plastic surface functional groups (i.e., with or without hydrophilic groups). By comparing carbon normalized log KF with literature data, the organic affinity of PE fiber was found to be 1-2 orders of magnitude lower than that of vectors, such as carbonaceous geosorbents (CG), but was 1-2 orders of magnitude higher than that of marine sediments. Small size and rough surface tended to enhance the sorption of plastic fibers of phenanthrene. In addition, phenol (log KOW : 1.46), a low-hydrophobicity compound, showed approximately 3 orders of magnitude lower sorption amounts onto both fibers compared to phenanthrene (log KOW : 4.46), indicating the selectivity of hydrophobicity. The results of this study demonstrate that the high abundance of plastic fibers distributed in mariculture farms could lead to a higher contaminant transfer effect than marine sediments, and their effects on cultured seafood (e.g., crab and fish) need further investigation.