Influence of sediment redox conditions on uranium mobilisation during saline intrusion

Abstract

In the UK, several coastal nuclear sites have been identified as vulnerable to future sea level rise. Legacy contamination at these sites has accumulated in sub-surface sediments at risk of future seawater inundation and intrusion. Porewater salinization, changes in pH and the influx of oxygen into sediments may impact the stability of sediment associated uranium (U). In this study, saturated column experiments were performed to compare the mobilisation of U from oxic and reduced sediments into seawater under environmentally relevant flow conditions. Uranium release profiles were independent of the initial geochemistry of the sediments. Uranium release from the sediments was kinetically controlled, showing relatively slow Highlights • Seawater intrusion promotes U mobilisation from oxic and reduced sediments • Initially reducing conditions result in stronger binding of U to the sediment • Mobilisation was pH dependent and kinetically controlled • Fe(III) phases formed during Fe(II) oxidation retard U release temporarily

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

“…This experimental approach, however, has the potential disadvantages of preferential flow paths, transport-limited rather than surface-limited reactions, and non-uniform contact of the reactant solution with surfaces (Steefel and Maher, 2009;Zhu, 2009). Column experiments have been used to study the release of U from contaminated soils and sediments under different environmental conditions (Qafoku et al, 2005;Liu et al, 2008;Eagling et al, 2013). However, no studies have reported dissolution rates of uranyl oxyhydroxide minerals under thermodynamically undersaturated and/or dynamic conditions of flow within porous media to simulate subsurface conditions.…”

From soil to sea: the role of groundwater in coastal critical zone processes

“…However, increasing ionic strength was shown to have a minor effect on mobilization of Cd, Cu, Pb, and Zn from marine sediments compared to physical disturbance and pH changes . These processes interact, as displacement of protons due to ion exchange can change pH . Wong et al showed experimentally that exposure of coastal lowland acid sulfate soils to seawater drives ion exchange and increases acidity, resulting in a pulsed release of Al, Fe, Ni, Mn, and Zn.…”

“…Wong et al showed experimentally that exposure of coastal lowland acid sulfate soils to seawater drives ion exchange and increases acidity, resulting in a pulsed release of Al, Fe, Ni, Mn, and Zn. An increase in pH due to exposure of reduced sediments to oxygenated seawater was shown to mobilize U from sediments from a coastal nuclear site in the UK …”

Evaluasi Sistem Pengendapan Uranium Pada Batuan Sedimen Formasi Sibolga, Tapanuli Tengah

“…Pengendapan mineral radioaktif berupa uraninite, carnotite, dan coffinite terbentuk pada proses redoks dengan kondisi reduksi yang dipengaruhi oleh kandungan material organik yang cukup tinggi [15] sehingga keterdapatannya hanya terbentuk pada serpih hitam yang kaya akan material organik [3]. Pengendapan uranium pada batuan sedimen berasal dari arah timur dan mengikuti arah aliran air tanah membentuk beberapa pola alur yang berarah timur laut-barat daya.…”