Spatiotemporal distribution characteristics and recycling potentials of the hibernating stock of retired mobile phones in China

China's accumulating stock of hibernating retired mobile phones, driven by rapid upgrades, represents a strategic “urban mine” resource. Based on the sales and update method and the spatial allocation method, this study estimated the hibernating stock of retired mobile phones in China at the provincial level from 2009 to 2024, analyzed their spatiotemporal distribution, and further assessed their recycling potential by distinguishing the proportions and material compositions of feature phones and smartphones at different phases. The results show that the hibernating stock of retired mobile phones increased from 25 million units in 2009 to 407 million units in 2024, totalling 4.1 billion units. It displays a geographical distribution that progressively declines from the coastal districts in the southeast to the interior regions in the northwest. In terms of total metal stock, the cumulative amount of metal resources from 2009 to 2024 is estimated at 51.01 tons of gold (Au), 504.06 tons of silver (Ag), 88.48 thousand tons of aluminum (Al), 68.93 thousand tons of copper (Cu), 45.13 thousand tons of iron (Fe), and a total of 71.65 thousand tons of seven other metals, including cobalt (Co), lithium (Li), chromium (Cr), lead (Pb), barium (Ba), zinc (Zn) and nickel (Ni). This study reveals significant spatial and temporal heterogeneity in the hibernating stock of retired mobile phones in China, providing a scientific basis for developing adaptable region-specific collection strategies.