Leaching of carbon, metals, and additives from microplastics to water

The occurrence of microplastics (MPs) has been evidenced worldwide in various aquatic environments, and while quite many studies have been devoted to the quantification and characterisation of these MPs, the knowledge of potential leaching from MPs to water is yet limited. In the current study, a range of different MPs prepared from consumer plastic products were soaked in water for 12 weeks, and variable composition of the water leachates was continuously analysed. Majority of investigated MPs released substantial amounts of dissolved organic carbon, with the maximum of approximately 65 mg per g of MPs after the 12 weeks, and some MPs also released dissolved inorganic carbon. Additionally, up to 10 other elements were detected in individual leachates – including metals (Al, Ba, Ca, Fe, K, Mg, Mn, Na, Zn) and one metalloid (Si). Out of those, Ca, K, and Na occurred most frequently, while Ca reached the highest values (up to approximately 2.5 mg per g MPs). In general, the overall highest leaching was observed in the case of MPs comprising polyurethane, polyvinyl chloride, and acrylonitrile-butadiene copolymer as the main polymers. Another general observation is that the leaching was usually most rapid during the first few weeks of MP contact with water. Further, in order to provide a better insight into composition and properties of the leachates, non-target analysis was conducted, and dozens of chemical individuals were tentatively identified in the leachates. Considering that the amounts of some elements released from MPs were quite high, and that some of the tentatively identified compounds are considered harmful to human health and/or to the environment, the leaching from MPs to ambient water might be important from different perspectives, including toxicology as well as fluxes of carbon and metals.