Assessing depleted uranium (DU) contamination of soil, plants and earthworms at UK weapons testing sites

Abstract

Depleted uranium (DU) weapons testing programmes have been conducted at two locations within the UK. An investigation was therefore carried out to assess the extent of any environmental contamination arising from these test programmes using both alpha spectrometry and mass spectrometry techniques. Uranium isotopic signatures indicative of DU contamination were observed in soil, plant and earthworm samples collected in the immediate vicinity of test firing points and targets, but contamination was found to be localised to these areas. The paper demonstrates the superiority of the 235 U: 238 U ratio over the 234 U: 238 U ratio for identifying and quantifying DU contamination in environmental samples and also describes the respective circumstances under which alpha spectrometry or mass spectrometry may be the more appropriate analytical tool. IntroductionNatural uranium (U) principally consists of three isotopes, primordial 238 U (t 1/2 = 4.47x10 9 y) and 235 U (t 1/2 = 7.04x10 8 y), which are parent members of natural radioactive decay series, and 234 U (t 1/2 = 2.45x10 5 years), which is a member of the 238 U decay chain. For natural U, the 235 U: 238 U activity ratio has a constant value 0.046 (Table 1), while the 234 U: 238 U activity ratio is variable as a consequence of decay chain disequilibrium that arises from preferential transfer of 234 U to surface and groundwater. 1,2 This disequilibrium results in pronounced 234 U: 238 U activity ratio variations, but for soils the commonly observed range is 0.8 -1.2 (e.g. 3,4 ). Depleted uranium (DU) is a byproduct of U enrichment processes, whereby the fissile isotope 235 U is preferentially concentrated for the production of nuclear fuel or nuclear weapons. The enrichment processes, e.g. gas centrifugation or gaseous diffusion, also separate 234 U from 238 U, leaving a waste material (DU) which is depleted with respect to both 234 U and 235 U. Although the exact isotopic composition of DU, particularly that used by the British military, has been determined on relatively few occasions 5,6 and thus may exhibit some subtle variation, DU has an isotopic signature strikingly distinct from naturally occurring U (Table 1). This isotopic difference can be used to identify and quantify contamination in the environment arising from the use of DU munitions, with both the 234 U: 238 U and 235 U: 238 U ratios being potentially useful for this purpose.Due to its high density (19.05 g cm -3 ), penetrating power and pyrophoric properties, DU has been used for military purposes such as tank-piercing ammunition and tank armour. In the UK alone, research and development of DU munitions dates back to the 1960s, with test programmes having been conducted at several Ministry of Defence (MoD) sites. The environmental fate of DU has, however, only recently begun to receive attention in the scientific literature, mostly in relation to areas such as the former Yugoslavia 7-14 and the Persian Gulf 15, 16 where DU munitions have been used in active warfare. While such studies have successfull...

On the possible role of macrofungi in the biogeochemical fate of uranium in polluted forest soils

“…Little is known about the geochemical behavior and fractionation of U in polluted soils. Several authors have investigated the biogeochemical fate of DU in polluted environments [6,[38][39][40] but none of these authors focused on forest soils. Results from sequential extraction for U in forest soils were published by Virtanen et al [41] but these authors studied various size fractions of four different mineral soils from an unpolluted boreal area.…”

Bioaccumulation and biological effects in the earthworm Eisenia fetida exposed to natural and depleted uranium

“…Recently, growing concern has arisen regarding the DU released from munitions employed in conflict areas, such as the Middle East and Kosovo (Bem and Bou-Rabee, 2004;Jia et al, 2004Jia et al, , 2005Di Lella et al, 2005), as well as weapons testing sites (Bleise et al, 2003;McClain et al, 2001;Oliver et al, 2007Oliver et al, , 2008. While chemical toxicity of natural U is considered to be identical to DU, radiological toxicities are different, since DU emits around 40% less radiation than natural U (Craft et al, 2004).…”

Depleted Uranium

“…In uranium mining areas, ingestion has been found to range between 13 and 18 μg/day (ATSDR, 1999;Harley, 1999). A number of studies have demonstrated increased uranium levels in the soil in these sites several years after the conflict (Sansone et al, 2001a,b;Danesi et al, 2003a,b;Durante and Pugliese, 2003;Bem and Bou-Rabee, 2004;Di Lella et al, 2004, 2005Jia et al, 2005Jia et al, , 2006Oliver et al, 2007Oliver et al, , 2008aZunic et al, 2008;Giovanetti et al, 2010). A number of studies have demonstrated increased uranium levels in the soil in these sites several years after the conflict (Sansone et al, 2001a,b;Danesi et al, 2003a,b;Durante and Pugliese, 2003;Bem and Bou-Rabee, 2004;Di Lella et al, 2004, 2005Jia et al, 2005Jia et al, , 2006Oliver et al, 2007Oliver et al, , 2008aZunic et al, 2008;Giovanetti et al, 2010).…”