Multi-scale investigation of uranium attenuation by arsenic at an abandoned uranium mine, South Terras

Abstract

Detailed mineralogical analysis of soils from the UK's historical uranium mine, South Terras, was performed to elucidate the mechanisms of uranium degradation and migration in the 86 years since abandonment. Soils were sampled from the surface (0-2 cm) and near-surface (25 cm) in two distinct areas of ore processing activities. Bulk soil analysis revealed the presence of high concentrations of uranium (<1690 p.p.m.), arsenic (1830 p.p.m.) and beryllium (~250 p.p.m.), suggesting pedogenic weathering of the country rock and ore extraction processes to be the mechanisms of uranium ore degradation. Micro-focus XRF analysis indicated the association of uranium with arsenic, phosphate and copper; µ-XRD data confirmed the presence of the uranylarsenate minerals metazeunerite (Cu(UO 2 ) 2 (AsO 4 ) 2 ·8H 2 O) and metatorbernite (Cu(UO 2 ) 2 (PO 4 ) 2 ·8H 2 O) to be ubiquitous. Our data are consistent with the solid solution of these two uranyl-mica minerals, not previously observed at uranium-contaminated sites. Crystallites of uranyl-mica minerals were observed to coat particles of jarosite and muscovite, suggesting that the mobility of uranium from degraded ores is attenuated by co-precipitation with arsenic and phosphate, which was not previously considered at this site.

Multiple environmental factors influence 238U, 232Th and 226Ra bioaccumulation in arbuscular mycorrhizal-associated plants

“…It has been observed that U minerals at South Terras are Cu-phosphate and Cu-arsenate rich, such as metatorbernite and metazeunerite, and were present at depths of ~25 cm (Corkhill et al, 2017;Foulkes et al, 2017;Purvis et al, 2004), consistent with the rhizosphere soils analysed here. In addition to a close association between U, Cu and P in these soils, Cu and P showed similar chemical behaviour to U as determined by sequential extraction analysis (Corkhill et al, 2017). Therefore plant roots and/or mycorrhizal hyphae accessing essential Cu and PO 4 3nutrients from the soil might coincidentally bioaccumulate 238 U.…”

“…South Terras and Needle's Eye are two ideal field locations for the characterisation of radionuclide transfer from soil into the understory vegetation of temperate woodland. While there has previously been substantial radiochemistry research at Needle's Eye and, to a lesser extent, South Terras (Basham et al, 1991;Corkhill et al, 2017;Foulkes et al, 2017;MacKenzie et al, 1991;Siddeeg et al, 2015), no previous study has investigated the radioecology of these sites. Both locations have soils with 238 U concentrations that greatly exceed the global average (UNSCEAR, 2000) and were similar to or exceeded values determined by a number of radioecology surveys (Blanco Rodriguez et al, 2010;Vera Tomé et al, 2003;Vera Tomé et al, 2002).…”

“…Elevated concentrations of 238 U and 226 Ra are present at South Terras because of historic uranium mining, which occurred on site until the early 1900's (Siddeeg et al, 2015). Secondary uranium ores torbernite and autunite have been identified at South Terras, with organic soils overlaying many of the remaining mine spoil heaps, which in turn sit astride predominantly gravel, sand and silt layers (Corkhill et al, 2017;Purvis et al, 2004;Read et al, 1991). Read et al (1991) should be referred to for a detailed description of the geochemistry and hydrogeology of South Terras.…”

Synthesis, characterisation and corrosion behaviour of simulant Chernobyl nuclear meltdown materials

“…40 Linear regression of the U L III edge energy position (defined as the energy where the edge step is equal to 0.5) with respect to standards of known oxidation state (UO 2 , Yb 0.5 U 0.5 Ti 2 O 6 and CaUO 4 ) confirmed the uranium oxidation state within the sample. 41…”

A multi-technique study of altered granitic rock from the Krunkelbach Valley uranium deposit, Southern Germany

“…This causes additional hazards associated with the release of As into water aquifers. [18][19][20][21][22][23][24] In cases when reduction conditions prevail, such as at the Ruprechtov site in the Czech Republic, As occurs in the form of arsenopyrite (FeAsS) in tertiary sediments forming layered aggregates with secondary uraninite and arsenopyrite. 19 Mixed copper uranyl arsenate-phosphate species have been identied in the soils from an abandoned U mine in the UK as a result of many years of the mining activities at the site.…”