Plastics are used in every aspect of modern life. Plastic items from land-based activities can enter the sea through different routes, as well as from sea-based activities, often accumulating in the coastal zones where they are commonly found washed up on beaches. Plastics may have trace elements associated with them, either inherent in the form of additives and non-intentionally added substances (NIAS) or adsorbed from the surrounding environment. With changing environmental conditions, including ingestion by organisms, these trace elements have the potential to be released from the plastic. The concentrations of trace elements that are associated with beached plastic may change depending on urbanisation, industrialisation, geological characteristics, polymer type, item function, and even colour.
A lack of knowledge exists around the concentrations of trace elements associated with beached plastic debris in Aotearoa / New Zealand, and their bioaccessibility is under-studied worldwide. This study engaged citizen scientists to collect beached debris from 21 locations around Aotearoa / New Zealand. Inductively coupled plasma – mass spectrometry was used to analyse a range of trace elements that are known environmental pollutants or common plastic additives. The proportion of trace elements bioaccessible to marine invertebrate and vertebrates using gastric fluid simulants was determined using two commonly collected items; lollipop sticks and firework casings.
Trace elements were detected at a wide range of concentrations, with pigments identified as the dominant source of elevated concentrations. A varying proportion of trace elements were made bioaccessible depending on the item, simulant, and trace element. This pioneering study of contaminants associated with plastic beach debris in Aotearoa / New Zealand has identified that trace elements used as pigments may pose a risk to wildlife due to the very high concentrations present, and their ability to disassociate from the plastic under simulated gastric conditions.