Hydrogeochemistry of Alkaline Steel Slag Leachates in the UK
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Drainage from steel slag disposal sites can be extremely alkaline and a source of pollution to surface and ground waters. Data is presented detailing the hydrogeochemistry of seven highly alkaline (pH > 10) steel slag surface discharges in the UK. While there is the consistent presence of Ca–OH type groundwater in all the discharges, there are clear disparities in hydrochemical facies within and between sites, reflecting native hydrochemistry, source material and hydrogeological setting. The longevity of the pollution problem from steel slag disposal sites is highlighted at one site where the water quality records date back three decades. The consistent presence of Al, B, Ba, Fe, Sr, V and occasional presence of Cr, Mo, Ni, Pb were found at concentrations typically below surface water quality standards in the leachates. Some of the monitored metals (Al, Fe, Ni, V) were found to be lost from solution downstream of emergence in calcite-dominated precipitates which rapidly form at all sites at rates up to 100 g m−2 day−1. The low concentrations of potentially problematic trace elements in both solution and the sediments are discussed with regard development of economically viable passive treatment wetlands for highly alkaline industrial discharges.
KeywordsSteel slag Leachate Alkaline Remediation Wetland
This research was funded by ENTRUST through Corus Group and the Mineral Industry Research Organisation (MIRO) under project RC 174 and the Natural Environment Research Council under project NE/F014465/1. Sarah Smith at Corus Group is thanked for funding the work at Coatham Marsh. Lisa Smith (Corus Group Scunthorpe) is thanked for assistance with sampling. The assistance of Jane Davis and Patrick Orme are in undertaking some of the laboratory analyses is gratefully acknowledged while Kath Liddell is thanked for performing XRD analyses. The authors are indebted to Diane Steele and Mark Merrix at the Environment Agency (Northumbria) for providing archival data for the Consett discharges. The comments of two anonymous reviewers are also greatly appreciated in improving the final version of the manuscript.
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