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Mobilization and bioaccessibility of cadmium in coastal sediment contaminated by microplastics

Marine Pollution Bulletin 2019 40 citations

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Plastics containing cadmium (a toxic heavy metal once common in plastic pigments) were ground into microplastic-sized fragments and mixed with coastal sediment; the cadmium was mobilized and became more available to organisms under certain conditions. This shows microplastics can carry and release toxic metals into marine environments.

Body Systems
Study Type Environmental

Cadmium has had a number of historical applications in plastics but is now highly regulated. In this study, plastics containing pigmented or recycled Cd at concentrations up to 16,300 μg g were processed into microplastic-sized fragments and added to clean estuarine sediment. Plastic-sediment mixtures (mass ratio = 1:100) were subsequently exposed to fluids simulating the digestive conditions encountered in marine deposit-feeding invertebrates prepared from a protein and a bile acid surfactant in seawater and the mobilization of Cd measured as a function of time. Kinetic profiles over a six-hour period were complex, with some fitted using a diffusion model and others exhibiting evidence of Cd interactions between the plastic and sediment surface. The maximum concentration of Cd released from plastic-sediment mixtures was about 0.8 μg g and orders of magnitude greater than Cd mobilization from sediment alone. It is predicted that large communities of deposit-feeders could mobilize significant quantities of Cd from historical microplastics.

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