This study surveyed the environmental pollution impacts of a steel slag recycling site located in Dangjin, Korea. Approximately 257,000 tons of steel slag were used, and public concerns were raised due to turbidity and high pH leachate observed after rainfall events. To assess potential contamination, analyses and field surveys were conducted, including leaching tests, up-flow leaching tests, and environmental monitoring of soil, groundwater, and surface water. The steel slag samples met the national regulatory limits for all detected heavy metals, cyanides, and fluorides. However, the pH of the slag was elevated, ranging from 8.1 to 10.4. Soil analysis results showed that the concentration of contaminants was below the Korean soil contamination concern standard and no direct evidence of slag contamination was found. Groundwater and surface water quality also met drinking water and environmental standards, although slightly higher pH and fluoride levels were observed at some locations, which were more likely attributable to local geological conditions rather than the slag. Overall, this study confirmed that the steel slag used in the field is environmentally recyclable. However, high pH may pose a potential risk to the surrounding ecosystem. Therefore, long-term maturation, pH control, and long-term environmental monitoring are necessary to ensure the safe and sustainable reuse of steel slag in land reclamation and construction.

Keywords: Free CaO, Steelmaking slag, Slag recycling site, Leachate, Alkaline leachate, Slag aging