Evaluation of testing approaches for constituent leaching from electric arc furnace (EAF) slags

Increased usage of electric arc furnace (EAF) slags as soil amendments and surface aggregates raises concerns regarding heavy metal release. However, no standardized leaching characterization approach exists for EAF slags and other industrial materials. This study compares test results for three EAF slags using several testing approaches: (i) total content analysis, (ii) single-batch extractions (i.e., TCLP, SPLP, and in-vitro bioaccessibility assay), and (iii) evaluation for the fine fraction (<2 mm) and ingestion fraction (<250 μm). Test results were compared to the pH-dependent liquid-solid partitioning (LSP) and percolation column testing. Constituent screening based on total content identified As, Cr, Fe, Li, Mn, Sb, Se, Tl and V as constituents of potential concern (COPCs); however, pH-dependent LSP curves indicated that only Fe, Mn, and possibly Cr have the potential to exceed regional residential soil screening levels. Additional COPCs (Al, Ba, Cd, Cu, Cr(VI), Hg, Mo, Ni, Pb, and Sn) exceeded example thresholds at one or more of three plausible release conditions. LSP curves and column test results indicated that most COPCs are in equilibrium at test conditions. Although leaching evaluation indicated the potential for concentrations greater than thresholds, assessments incorporating test results with scenario-specific parameters provide a more precise basis for evaluating COPC release. This study demonstrates that the applicability of single-batch extraction tests is limited to conditions simulated by the test, while a well-defined LSP curve is representative of leaching over conditions of all single-batch tests. Therefore, pH-dependent and percolation column testing provides a baseline characterization to support environmental decision making.