Ecological Risk Assessment of Nickel Leaching from Ferronickel Slag-Containing Concrete Using Species Sensitivity Distribution

Ferronickel slag is a by-product generated during the production of raw materials for stainless steel. In recent years, it has attracted attention as a potential alternative to natural resources for use in infrastructure in marine environments; however, concerns remain regarding nickel release and its potential ecological implications. This study evaluated nickel leaching from ferronickel slag-containing concrete by combining species sensitivity distribution (SSD) analysis for marine organisms with leaching experiments. The SSD analysis, based on EC10 values, yielded a hazardous concentration for 5% of species (HC5) of 6.09 µg/L for nickel. Concrete blocks (cylindrical shape; diameter, 10 cm; height, 20 cm; surface area, 0.0785 m2) were prepared with ferronickel slag replacing natural fine aggregate at proportions ranging from 0 to 60%, and leaching tests were conducted using artificial seawater (35 PSU). Nickel concentrations appeared to reach a plateau at higher replacement ratios (45% and 60%). Using the SSD-derived HC5 under a conservative closed-system assumption, which represents a worst-case scenario for screening purposes, the maximum allowable surface area of slag-containing concrete was estimated to range from 0.186 to 1.473 m2/L, suggesting that the potential for adverse ecological effects in marine environments is expected to be limited under conditions where dilution and dispersion occur. This integrated approach provides screening-level insight into the environmentally responsible utilization of ferronickel slag in marine applications.