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Ikaite formation in streams affected by steel waste leachate: First report and potential impact on contaminant dynamics

Bastianini, Laura; Rogerson, Mike; Brasier, Alex; Prior, Timothy J.; Hardman, Kit; Dempsey, Eddie; Bird, Anna; Mayes, William M.


Laura Bastianini

Mike Rogerson

Alex Brasier

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Dr Tim Prior
Senior Lecturer in Inorganic Chemistry

Kit Hardman

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Dr Eddie Dempsey
Senior Lecturer in Structural Geology and Geohazards


Highly alkaline (pH 9–12) waters can arise from a range of globally significant and environmentally impactful industrial processes such as lime, steel and cement production, alumina refining and energy generation (e.g. combustion ashes). Such residue storage sites are often characterized by extreme geochemical conditions that can be hazardous to aquatic life but are quickly becoming a critical focus for resource recovery and carbon capture initiatives. The very high rates of mineral precipitation at these sites can give rise to the formation of transient minerals that are not currently well understood. As such our estimates of carbon budgets and understanding of trace metal dynamics at highly alkaline sites is currently limited. This study provides a significant advancement in the basis for characterising hyperalkaline carbonate systems through identification and chemical analysis of transient minerals forming in sites receiving high pH (>11) steel slag leachate in northern England. Whilst most of the secondary deposits at the study sites appear to be dominated by calcite, this study provides the first account of ikaite (CaCO3.6H2O) crystallization within steel-slag leachate, using novel field (Fourier Transform Infra-Red) supported by rapid laboratory (X-Ray Diffraction) validation. This study suggests that ikaite is a secondary mineral with a primary phase being amorphous calcium carbonate (ACC). Trace element analysis of ikaite forming in these steel-slag leachate affected waters is demonstrates its strong affinity to incorporate relatively large inventories of potentially harmful metals (e.g. lead and cadmium). Importantly, ikaite is only stable at low temperatures (−4 to 8 °C) and thus is of significant concern given its potential to release hazardous pulses of contamination during warming events in the spring. The findings provide an improved understanding of carbonate precipitation processes at highly alkaline sites which in turn should influence future research endeavours around mineral carbonation, trace metal dynamics and environmental remediation at these sites globally.


Bastianini, L., Rogerson, M., Brasier, A., Prior, T. J., Hardman, K., Dempsey, E., …Mayes, W. M. (2024). Ikaite formation in streams affected by steel waste leachate: First report and potential impact on contaminant dynamics. Chemical Geology, 644, Article 121842.

Journal Article Type Article
Acceptance Date Nov 18, 2023
Online Publication Date Nov 26, 2023
Publication Date Jan 20, 2024
Deposit Date Nov 27, 2023
Publicly Available Date Dec 11, 2023
Journal Chemical Geology
Print ISSN 0009-2541
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 644
Article Number 121842
Keywords Ikaite; Alkaline sites; Carbonate systems; Carbon capture; Trace metal dynamics
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