The influence of cosmetic microbeads on the sorptive behavior of cadmium and lead within intertidal sediments: A laboratory study

Concentrations of microplastics within two geographically distinct urban locations within Burrard Inlet, British Columbia (BC), and the influence of facial scrub microbeads on lead and cadmium sorption within intertidal sediments were determined. Bulk intertidal sediment sampled from Cates Park (CP) located within the protected part of the inlet contained greater concentrations of microplastics (5560/kg wet sediment) as compared to Horseshoe Bay (HSB) (3120/kg wet sediment) located on the exposed open part of the inlet. Of the recovered microplastics ca. 75% were characterized as microbeads. Laboratory controlled microcosm experiments in which microbeads separated from a commercial facial scrub were added to bulk sediments collected from CP at ambient and 10-fold ambient (high) concentrations indicated that the microbeads acted as sorption sites. At ambient concentrations, less lead was recovered from pore water and surface water of treatment as compared to control microcosms. At high concentrations, the microbeads acted as a contaminant source to the microcosms, notably cadmium. Sorption of lead to microbeads has important implications for the potential role of microplastics, in this case microbeads acting as a yet quantified link in aquatic food webs.