Operational speciation of uranium in inter-tidal sediments from the vicinity of a phosphoric acid plant by means of the BCR sequential extraction procedure and ICP-MS

Abstract

A method has been developed for the determination of uranium in sediment digests and sequential extracts by ICP-MS. No interferences were found due to the presence of the extractant matrices (0.11 mol l(-1) acetic acid, 0.1 mol l(-1) hydroxylammonium chloride, 1.0 mol l(-1) ammonium acetate and 30% v/v aqua regia) provided U-236 was used as internal standard and the samples were diluted 5-fold with 5% v/v nitric acid prior to analysis. Detection limits (8 ng g(-1) for extracts and 20 ng g(-1) for digests) were adequate for determination of uranium at environmental levels. Results obtained by ICP-MS for aqua regia digests were slightly lower than those obtained by alpha spectrometry, but overall recoveries of uranium by sequential extraction were generally within +/- 10% of pseudototal values. Application of the developed method to inter-tidal sediments collected from the vicinity of the Albright and Wilson phosphoric acid plant, Whitehaven, Cumbria, confirmed the presence of significant technological enhancement of uranium at Whitehaven Harbour but showed that concentrations had decreased since the plant discontinued phosphate ore processing in 1992. Results of the sequential extraction suggested that spillage of phosphate ore (containing up to 120 mu g g(-1) uranium) during shipping may have made a significant contribution to the environmental contamination observed

Uranium Speciation and Bioavailability in Aquatic Systems: An Overview

“…Desideri et al [89] used a fivestage sequential extraction protocol [93] to partition U from several marine sediments into water soluble, acid soluble, carbonate, reducible, and residual sediment fractions. In contrast to the results of Howe et al [87], U was associated primarily with the carbonate and residual sediment fractions.…”

“…A number of studies [86,87,88,89,90,91] have employed sequential extraction to indirectly determine the speciation of U in sediments or suspended particulate matter. Howe et al [87] used a three-stage sequential extraction protocol [92] to partition U from Whitehaven Harbour (U.K.) sediment into exchangeable (water and acid soluble), oxidizable (bound to Fe and Mn oxyhydroxides), reducible (bound to organic matter and sulfides), and residual (insoluble) fractions.…”

“…Howe et al [87] used a three-stage sequential extraction protocol [92] to partition U from Whitehaven Harbour (U.K.) sediment into exchangeable (water and acid soluble), oxidizable (bound to Fe and Mn oxyhydroxides), reducible (bound to organic matter and sulfides), and residual (insoluble) fractions. Although the distribution of U in the sediment samples was somewhat variable, it was predominantly (40 to 80%) associated with the oxidizable fraction.…”

Is there a future for sequential chemical extraction?

“…503 Sequential extraction procedures have been applied to investigate uranium geochemistry in rivers, 504 fertilizeramended soils 505 and Moroccan black shale oil. 506 Environmental contamination arising from uranium mining [507][508][509] and the technological enhancement of natural radionuclides by phosphates mining 510 and production, [511][512][513] coal burning and pyrite roasting 514 and other industrial processes 515 have been investigated. Studies have indicated that relatively small proportions of the transuranic elements plutonium and americium occur in easily extractable forms in contaminated soil [516][517][518] and sediment.…”

Soil Chemical Pollution, Risk Assessment, Remediation and Security

“…The identification of definite geochemical associations of metallic elements in polluted solids has been seriously questioned (see above). Chemical extractions are not geochemical association-specific (e.g., Howe et al, 1999).…”