Immobilisation of geogenic arsenic and vanadium in iron-rich sediments and iron stone deposits

• Published in: The Science of the total environment 2019-03, Vol.654, p.1072-1081
• Main Authors: Mikkonen, Hannah G., van de Graaff, Robert, Collins, Richard N., Dasika, Raghava, Wallis, Christian J., Howard, Daryl L., Reichman, Suzie M.
• Format: Article
• Language: English
• Subjects: Arsenic; Iron stone; Synchrotron; Vanadium; X-ray absorption near edge spectroscopy; X-ray fluorescence
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.10.427

Determination of how geogenic arsenic (As) and vanadium (V) is mobilised from naturally-enriched soils and iron (Fe) stones is integral for understanding the potential risk to the environment from changed land use conditions. Thus, the association of As, V and Fe in As-enriched sediments and Fe stones in Tertiary sediments of Melbourne, Australia, was assessed using chemical extraction methods, micro focused X-ray fluorescence and X-ray absorption spectroscopy. We show that the selective association of As with Fe during Fe stone formation has resulted in As enrichment of up to 60 times the concentration of surrounding soils, and 1000 times higher than mean As concentrations in world soils. In both soil and Fe stones, As was distributed with goethite as arsenate and relatively immobile under oxic conditions. The presence of V on the outer edge of the assessed Fe stone provided evidence of differences in historical As and V solubility; that is, As was immobilised by Fe during an earlier stage of Fe stone formation than V. [Display omitted] •Iron stones comprised up to 6700 mg/kg arsenic and 1360 mg/kg vanadium.•Arsenic was present as arsenate with goethite.•Arsenic and vanadium in iron stones had low leachability.•Iron stone banding provides an indication of differences in vanadium and arsenic historical solubility.