Greening a Steel Mill Slag Brownfield with Biosolids and Sediments: A Case Study.

The former US Steel Corporation's South Works site in Chicago, IL, is a 230-ha bare brownfield consisting of steel mill slag fill materials that will need to be reclaimed to support and sustain vegetation. We conducted a case study to evaluate the suitability of biosolids and dredged sediments for capping the steel mill slag to establish good quality turfgrass vegetation. Eight study plots were established on a 0.4-ha parcel that received biosolids and dredged sediment blends of 0, 25, 50, or 100% biosolids (v/v). Turfgrass was successfully established and was thicker and greener in biosolids-amended sediments than in unamended sediments. Concentrations of N, P, K, and micronutrients in turfgrass tissues increased with increasing biosolids. Soil organic carbon, N, P, and micronutrients increased with increasing biosolids. Cadmium, Cu, Ni, and Zn concentrations in biosolids-amended sediments also increased with increasing biosolids but were far below phytotoxicity limits for turfgrass. Lead and Cr concentrations in biosolids-amended plots were comparable to concentrations in unamended sediments. Groundwater monitoring lysimeters and wells below the study site and near Lake Michigan were not affected by nutrients leaching from the amendments. Overall, the results from this case study demonstrated that blends of biosolids and dredged sediments could be successfully used for capping steel mill slag brownfield sites to establish good quality turfgrass vegetation.