Heavy metal risks and policy analysis on using industrial waste salts for making value-added snow-melting agents

Industrial waste salts are commonly used to make value-added snow-melting agents to ensure traffic safety in northern China during winter and spring after snowfall. However, heavy metals in industrial waste salts may pose certain environmental risks. Snow-melting agents and snow samples were collected and analyzed from highways, arterial roads, footbridges, and other locations in Beijing after the snowstorm in December 2023. It was found that the main component of snow-melting agents was sodium chloride with high concentrations of Cu, Mn, and Zn, which are not regulated in the current policies, despite the recent promotion of environmentally friendly snow-melting agents. The Pb, Zn and Cr contents of some snow samples exceeded the limitation value of surface water quality standards, potentially affecting the soil and water environment near roadsides, although the snow-melting agents comply with relevant standards, which indicates the policy gap in the management of recycled industrial salts. We reviewed and analyzed the relevant standards for snow-melting agents and industrial waste salts proposed nationally and internationally over the past 30 years. Through comparative analysis, we proposed relevant policy recommendations to the existing quality standards of snow-melting agents and the management regulations of industrial waste salts, and the formulation of corresponding usage strategies, aimed at reducing the potential environmental release of heavy metals from the use of snow-melting agents, thereby promoting more sustainable green urban development and environmentally sound waste management.