Geochemical and ecotoxicological assessment of iron- and steel-making slags for potential use in environmental applications

Prior to the productive use of iron- and steel-making slags as environmental amendments, a risk assessment supported by material characterization concomitant with leaching and ecotoxicological testing is necessary. Five iron- and steel-making slags were characterized geochemically, and the leachability of their elemental constituents was assessed. The toxicity of slag leachate to microalgae (Chlorella sp.), cladocerans (Ceriodaphnia dubia), and bacteria (Vibrio fischeri) was related to elemental composition. Slag leachates with the highest concentrations of dissolved elements were the most toxic (10% effective concentration [EC10] ∼1%), whereas those with the lowest concentrations of elements were the least toxic (EC10 63-85%). It was not possible to determine which elements caused the observed toxicity; however, comparisons with contaminant guidelines and published toxicity data identified several elements of potential environmental concern. Low to moderate activities were measured for radionuclides in the U and Th decay chains in slags. Based on these data, some of the slags examined herein are potentially suitable for use as environmental amendments following ≥10 times dilution to ameliorate potential toxic effects because of leachate pH.