| Summary: | Strontium-90 is present in contaminated land at nuclear sites around the world and is also an important component of nuclear waste inventories. The mobility of 90Sr in the subsurface is often controlled either by adsorption to sediment particle surfaces or incorporation reactions into secondary mineral precipitates. This thesis presents the results of a multidisciplinary study examining the behaviour of 90Sr in West Cumbrian unconsolidated aquifer sediments under a range of groundwater and anthropogenic liquor compositions relevant to contaminated land scenarios. Experiments using low ionic strength (IS) regional .groundwater at circumneutral pH found 90Sr was almost completely removed from solution. In higher IS artificial waste tank leachate (PH 11), sorption of 90Sr decreased, suggesting that higher concentration of ions in solution inhibited 90Sr sorption. In both scenarios, EXAFS data confirmed that Sr was present as an outer-sphere adsorption complex. Sorbed 90Sr remained exchangeable with MgCl2 even after one year. In contrast, experiments using pH 13.5 young cement water (YCW), found very high sorption despite the extremely high IS. EXAFS analysis of samples suggested that mineral alteration and the formation of secondary phases had occurred. Secondary phases initially sorbed Sr via inner-sphere adsorption, but in a sample aged for a year at 70 [degree]C there was evidence of Sr incorporation in a newly formed zeolite mineral which was identified as K-chabazite. Once incorporated, Sr was only desorbed using a pH 1.5 solution. Finally, experiments using Ca(OH)2 (PH 12.7) found no evidence of mineral alteration, and sorption was inhibited by the higher ionic strength present.
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