Uranium

Keith, Larry S.

doi:10.1016/b978-012369413-3/50100-2

Cited by 16 publications

(9 citation statements)

References 74 publications

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“…Conversely, recoil processes and the spontaneous oxidation of U 4+ to U 6+ during decay are reasons for preferential leaching of 234 U from soil, leaving it with AR < 1 and the leaching water with AR > 1 (Osmond and Cowart, 1976). The extent of 234/238 U disequilibrium depends on the characteristics of the disturbance and values of 0.8-10 in waterbodies, 0.8-8 in precipitation and 0.5-1.2 in soil have been reported (Keith et al, 2007). The contribution of fertilizer-derived U to soils, surface and groundwater can therefore be recognized by a shift in AR towards 1, which has been successfully used in a number of studies to trace the sources of U in soil and water (Conceicao and Bonotto, 2003;Zielinski et al, 1997Zielinski et al, , 2000Zielinski et al, , 2006.…”

Section: Introductionmentioning

confidence: 97%

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Uranium in agricultural soils and drinking water wells on the Swiss Plateau

Bigalke

Schwab

Rehmus

et al. 2018

Environmental Pollution

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Mineral phosphorus fertilizers are regularly applied to agricultural sites, but their uranium (U) content is potentially hazardous to humans and the environment. Fertilizer-derived U can accumulate in the soil, but might also leach to ground-, spring and surface waters. We sampled 19 mineral fertilizers from the canton of Bern and soils of three arable and one forest reference sites at each of four locations with elevated U concentrations (7-28 μg L) in nearby drinking water wells. The total U concentrations of the fertilizers were measured. The soils were analysed at three depth intervals down to 1 m for general soil parameters, total Cd, P, U and NaHCO-extractable U concentrations, and U activity ratios (AR). The U concentrations and AR values of the drinking water samples were also measured. A theoretical assessment showed that fertilizer-derived U may cause high U concentrations in leaching waters (up to approx. 25 μg L), but normally contributes only a small amount (approx. 0-3 μg L). The arable soils investigated showed no significant U accumulation compared to the forest sites. The close positive correlation of AR with NaHCO-extractable U (R = 0.7, p < 0.001) indicates that application of fertilizer can increase the extractable U pool. The lack of depth gradients in the soil U concentrations (1.5-2.7 mg kg) and AR (0.90-1.06) ratios are inconsistent with the accumulation of U in the surface soil, and might indicate some leaching of fertilizer-derived U. The AR values in the water samples were close to 1, possibly suggesting an influence of fertilizer-derived U. However, based on findings from the literature and considering the heterogeneity of the catchment area, the agricultural practices, and the comparatively long distance to the groundwater, we conclude that fertilizer-derived U makes only a minor contribution to the elevated U concentrations in the water samples.

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Section: Introductionmentioning

confidence: 97%

“…The 234 U/ 238 U alpha activity ratio (AR) is a tool to relate U to its source directly. In an undisturbed closed system, as is assumed in a phosphate rock deposit, a secular equilibrium becomes established and AR levels approach 1 (Figure 1; Bourdon et al, 2003;Keith et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Uranium in agricultural soils and drinking water wells on the Swiss Plateau

Bigalke

Schwab

Rehmus

et al. 2018

Environmental Pollution

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“…The number of radionuclide atoms present and thus toxicity of these radionuclides with very long half-lives may therefore be important. A recent epidemiological study suggests a higher chemical than radiological risk from 226 Ra [ 74 ], but it is also well known that uranium has a pronounced chemical toxicity that is more acute than its radiotoxicity [ 74 , 75 ]. Thus, with secular equilibrium for 226 Ra with progenitor radionuclides, the large number of uranium atoms and covariation with the distribution of 226 Ra could help explain the statistical results.…”

Section: Discussionmentioning

confidence: 99%

Reduced soil fauna decomposition in a high background radiation area

Haanes

Gjelsvik

2021

PLoS ONE

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Decomposition of litter and organic matter is a very important soil ecosystem function where soil fauna play an important role. Knowledge of the responses in decomposition and soil fauna to different stressors is therefore crucial. However, the extent to which radioactivity may affect soil fauna is not so well known. There are some results showing effects on soil fauna at uranium mines and near Chernobyl from relatively high levels of anthropogenic radionuclides. We hypothesize that naturally occurring radionuclides affect soil fauna and thus litter decomposition, which will covary with radionuclide levels when accounting for important soil parameters. We have therefore used standardised litterbags with two different mesh sizes filled with birch leaves (Betula pubescens) to assess litter decomposition in an area with enhanced levels of naturally occurring radionuclides in the thorium (232Th) and uranium (238U) decay chains while controlling for variation in important soil parameters like pH, organic matter content, moisture and large grain size. We show that decomposition rate is higher in litterbags with large mesh size compared to litterbags with a fine mesh size that excludes soil fauna. We also find that litter dried at room temperature is decomposed at a faster rate than litter dried in oven (60⁰C). This was surprising given the associated denaturation of proteins and anticipated increased nutritional level but may be explained by the increased stiffness of oven-dried litter. This result is important since different studies often use either oven-dried or room temperature-dried litter. Taking the above into account, we explore statistical models to show large and expected effects of soil parameters but also significant effects on litter decomposition of the naturally occurring radionuclide levels. We use the ERICA tool to estimate total dose rate per coarse litterbag for four different model organisms, and in subsequent different statistical models we identify that the model including the dose rates of a small tube-shape is the best statistical model. In another statistical model including soil parameters and radionuclide distributions, 226Ra (or uranium precursory radionuclides) explain variation in litter decomposition while 228Ra (and precursors) do not. This may hint to chemical toxicity effects of uranium. However, when combining this model with the best model, the resulting simplified model is equal to the tube-shape dose-rate model. There is thus a need for more research on how naturally occurring radionuclides affect soil fauna, but the study at hand show the importance of an ecosystem approach and the ecosystem parameter soil decomposition.

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“…At the same time, U(VI) is a heavy actinide with a long half-life of radioactive decay, high chemical and biological toxicity, and a non-biodegradable and carcinogenic nature which constitutes a great threat to human health. 3,4 To reduce these health risks, both World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA) set a guideline limit for total U(VI) content in drinking water at 30 ppb. 5 Uranium concentrations in the groundwater of the contaminated zone were much higher than the safety limit.…”

Section: Introductionmentioning

confidence: 99%