Enhanced desorption of persistent organic pollutants from microplastics under simulated physiological conditions

Source: ScienceDirect

Authors: Adil Bakir, Steven J. Rowland, Richard C. Thompson

Abstract

Microplastics have the potential to uptake and release persistent organic pollutants (POPs); however, subsequent transfer to marine organisms is poorly understood. Some models estimating transfer of sorbed contaminants to organisms neglect the role of gut surfactants under differing physiological conditions in the gut (varying pH and temperature), examined here. We investigated the potential for polyvinylchloride (PVC) and polyethylene (PE) to sorb and desorb 14C-DDT, 14C-phenanthrene (Phe), 14C-perfluorooctanoic acid (PFOA) and 14C-di-2-ethylhexyl phthalate (DEHP). Desorption rates of POPs were quantified in seawater and under simulated gut conditions. Influence of pH and temperature was examined in order to represent cold and warm blooded organisms. Desorption rates were faster with gut surfactant, with a further substantial increase under conditions simulating warm blooded organisms. Desorption under gut conditions could be up to 30 times greater than in seawater alone. Of the POP/plastic combinations examined Phe with PE gave the highest potential for transport to organisms.

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Plastic as a carrier of POPs to aquatic organisms: A model analysis.

Environ. Sci. Technol., Just Accepted Manuscript
DOI: 10.1021/es401169n
Publication Date (Web): June 11, 2013
Copyright © 2013 American Chemical Society

Abstract

It has been hypothesised that persistent organic pollutants (POPs) in microplastic may pose a risk to aquatic organisms. Here, we develop and analyse a conceptual model that simulates the effects of plastic on bioaccumulation of POPs. The model accounts for dilution of exposure concentration by sorption of POPs to plastic (POP ‘dilution’), increased bioaccumulation by ingestion of plastic containing POPs (‘carrier’), and decreased bioaccumulation by ingestion of clean plastic (‘cleaning’). The model is parameterised for the lugworm Arenicola marina and evaluated against recently published bioaccumulation data for this species from laboratory bioassays with polystyrene microplastic. Further scenarios include polyethylene microplastic, nano-sized plastic and open marine systems. Model analysis shows that plastic with low affinity for POPs, like polystyrene will have a marginal decreasing effect on bioaccumulation, governed by dilution. For stronger sorbents like polyethylene, the dilution, carrier and cleaning mechanism are more substantial. In closed laboratory bioassay systems, dilution and cleaning dominate, leading to decreased bioaccumulation. Also in open marine systems a decrease is predicted due to a cleaning mechanism that counteracts biomagnification. However, the differences are considered too small to be relevant from a risk assessment perspective.

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