Environmental behaviour of iron and steel slags in coastal settings

Riley, Alex L; Cameron, James; Burke, Ian T; Onnis, Patrizia; Macdonald, John M; Gandy, Catherine J; Crane, Richard A; Byrne, Patrick; Comber, Sean; Jarvis, Adam P; Hudson-Edwards, Karen A; Mayes, William M

Abstract

Iron and steel slags have a long history of both disposal and beneficial use in the coastal zone. Despite the large volumes of slag deposited, comprehensive assessments of potential risks associated with metal(loid) leaching from iron and steel by-products are rare for coastal systems. This study provides a national-scale overview of the 14 known slag deposits in the coastal environment of Great Britain (those within 100 m of the mean high-water mark), comprising geochemical characterisation and leaching test data (using both low and high ionic strength waters) to assess potential leaching risks. The seaward facing length of slag deposits totalled at least 76 km, and are predominantly composed of blast furnace (iron-making) slags from the early to mid-20th Century. Some of these form tidal barriers and formal coastal defence structures, but larger deposits are associated with historical coastal disposal in many former areas of iron and steel production, notably the Cumbrian coast of England. Slag deposits are dominated by melilite phases (e.g. gehlenite), with evidence of secondary mineral formation (e.g. gypsum, calcite) indicative of weathering. Leaching tests typically show lower element (e.g. Ba, V, Cr, Fe) release under seawater leaching scenarios compared to deionized water, largely ascribable to the pH buffering provided by the former. Only Mn and Mo showed elevated leaching concentrations in seawater treatments, though at modest levels (<3 mg/L and 0.01 mg/L, respectively). No significant leaching of potentially ecotoxic elements such as Cr and V (mean leachate concentrations <0.006 mg/L for both) were apparent in seawater, which micro-X-Ray Absorption Near Edge Structure (µXANES) analysis show are both present in slags in low valence (and low toxicity) forms. Although there may be physical hazards posed by extensive erosion of deposits in high energy coastlines, the data suggest seawater leaching of coastal iron and steel slags in the UK is likely to pose minimal environmental risk.

Citation

Riley, A. L., Cameron, J., Burke, I. T., Onnis, P., Macdonald, J. M., Gandy, C. J., …Mayes, W. M. (2024). Environmental behaviour of iron and steel slags in coastal settings. Environmental science and pollution research, https://doi.org/10.1007/s11356-024-33897-4

• Journal Article Type: Article
• Acceptance Date: May 31, 2024
• Online Publication Date: Jun 14, 2024
• Publication Date: Jan 1, 2024
• Deposit Date: May 31, 2024
• Publicly Available Date: Jun 17, 2024
• Journal: Environmental Science and Pollution Research
• Print ISSN: 0944-1344
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1007/s11356-024-33897-4
• Keywords: Iron and steel slag; Legacy Waste; Leachate Formation; Coastal Pollution; Synchrotron; Waste Geochemistry
• Public URL: https://hull-repository.worktribe.com/output/4693457