Consistent elemental leaching profiles from waste smartphones in aquatic systems

• The release of 51 elements from end-of-life smartphones in river water is consistent. • The leaching of trace elements from newer models is limited because of coating. • Water chemistry, especially dissolved complexing ligands, affects leachability. • The emissions of tin nano- and micro-particles are of particular concern. As the manufacture of electronic devices escalates to meet the demands of an increasingly technology-driven society, the impact of electronic waste (e-waste) on the environment becomes more prominent as a global issue. In particular, end-of-life small electronics (e.g. smartphones, personal computers) that escape e-waste collection and recycling processes frequently become environmentally burdensome. This study assesses the leaching patterns of inorganic elements from smartphones of several generations in natural river waters with different chemistries. We classified 51 elements into seven clusters with consistent behaviours under different testing conditions. Their leaching behaviours were related to their abundance in electronic components and technologies employed on the electronics, such as coatings that temporarily isolate the components from environmental media. Water chemistry, especially the abundance of complexing organic ligands, can also increase elemental mobility and leachability. Additionally, scanning electron microscopy revealed the emission of tin nano- and micro-particles from soldering points. Tin is essential in phasing out lead in soldering technologies. Nevertheless, the emission of tin nanoparticles from modern smartphones is concerning, and further studies are required on their ecotoxicity. In summary, more stringent directives on regulating recycling centers globally are needed to minimize the environmental footprint of electronic waste.