Coprecipitation of Uranium(VI) with Calcite: XAFS, micro-XAS, and luminescence characterization

Reeder, Richard J.; Nugent, M.; Tait, C. Drew; Morris, David E.; Heald, Steve M.; Beck, Kenneth M.; Hess, Wayne P.; Lanzirotti, Antonio

doi:10.1016/s0016-7037(01)00647-0

Cited by 193 publications

(229 citation statements)

References 41 publications

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“…[56] Uranium in the carbonate mineral fraction is likely incorporated into carbonate minerals in source materials and would not be released down gradient of the pond because calcite and aragonite have low solubility under the neutral to basic pH conditions of the sampling locations. [66,67] Aqueous U concentrations in surface waters (in Larson et al [4] ) support the lack of solubilised U at down gradient sites, with a U concentration 2 times background level (32.7 mg L À1 ) measured at Pete's Creek wetland and a below background level concentration (5.14 mg L À1 ) measured at the Bowman-Haley backwaters during summer sampling. [4] Aqueous U VI is expected to adsorb preferentially to amorphous iron oxides in sediments rather than to carbonate minerals.…”

Section: Geochemical Controls On U Transportmentioning

confidence: 87%

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Troyer

Stone

2014

Environ. Chem.

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Environmental context. Uranium and arsenic, two elements of human health concern, are commonly found at sites of uranium mining, but little is known about processes influencing their environmental behaviour. Here we focus on understanding the chemical and physical processes controlling uranium and arsenic transport at an abandoned uranium mine. We find that the use of sedimentation ponds limits the mobility of uranium; however, pond conditions at our site resulted in arsenic mobilisation. Our findings will help optimise restoration strategies for mine tailings.Abstract. Although As can occur in U ore at concentrations up to 10 wt-%, the fate and transport of both U and As at U mine tailings have not been previously investigated at a watershed scale. The major objective of this study was to determine primary chemical and physical processes contributing to transport of both U and As to a down gradient watershed at an abandoned U mine site in South Dakota. Uranium is primarily transported by erosion at the site, based on decreasing concentrations in sediment with distance from the tailings. Sequential extractions and U X-ray absorption near-edge fine structure (XANES) fitting indicate that U is immobilised in a near-source sedimentation pond both by prevention of sediment transport and by reduction of U VI to U IV . In contrast to U, subsequent release of As to the watershed takes place from the pond partially due to reductive dissolution of Fe oxy(hydr)oxides. However, As is immobilised by adsorption to clays and Fe oxy(hydr)oxides in oxic zones and by formation of As-sulfide mineral phases in anoxic zones down gradient, indicated by sequential extractions and As XANES fitting. This study indicates that As should be considered during restoration of uranium mine sites in order to prevent transport.

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Section: Geochemical Controls On U Transportmentioning

confidence: 87%

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Troyer

Stone

2014

Environ. Chem.

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“…Reeder and colleagues (e.g. Paquette and Reeder, 1995;Reeder et al, 2001) have demonstrated the crucial importance of differential ion incorporation at complementary growth sites around growth hillocks on rhombohedral surfaces. This factor was argued to account for scatter in partition coefficients experimentally determined at microscopic scale by , but data so far indicates that any heterogeneity of these growth sites appears to occur on a spatial scale smaller than that of the analytical points Treble et al, 2006).…”

Section: Trace Elements and Other Impuritiesmentioning

confidence: 99%

Modification and preservation of environmental signals in speleothems

Fairchild

Smith

Baker

et al. 2006

Earth-Science Reviews

736

506

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Speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system. However, the climatological meaning of many speleothem records cannot be interpreted unequivocally; this is particularly so for more subtle shifts and shorter time periods, but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward.An explicit description of speleothem records as time series draws attention to the nature and importance of the signal filtering processes by which the weather, the seasons and longer-term climatic and other environmental fluctuations become encoded in speleothems. We distinguish five sources of variation that influence speleothem geochemistry: atmospheric, vegetation/soil, karstic aquifer, primary speleothem crystal growth and secondary alteration and give specific examples of their influence. The direct role of climate diminishes progressively through these five factors.We identify and review a number of processes identified in recent and current work that bear significantly on the conventional interpretation of speleothem records, for example: 1) speleothem geochemistry can vary seasonally and hence a research need is to establish the proportion of growth attributable to different seasons and whether this varies over time.2) whereas there has traditionally been a focus on monthly mean δ 18 O data of atmospheric moisture, current work emphasizes the importance of understanding the synoptic processes that lead to characteristic isotope signals, since changing relative abundance of different weather types might 1 Corresponding author, fax +44(0)1214145528, E-mail: i.j.fairchild@bham.ac.uk control their variation on the longer-term. 3) the ecosystem and soil zone overlying the cave fundamentally imprint the carbon and trace element signals and can show characteristic variations with time. 4) new modelling on aquifer plumbing allows quantification of the effects of aquifer mixing. 5) recent work has emphasized the importance and seasonal variability of CO 2 -degassing leading to calcite precipitation upflow of a depositional site on carbon isotope and trace element composition of speleothems. 6) Although much is known about the chemical partitioning between water and stalagmites, variability in relation to crystal growth mechanisms and kinetics is a research frontier. 7) Aragonite is susceptible to conversion to calcite with major loss of chemical information, but the controls on the rate of this process are obscure.Analytical factors are critical to generate high-resolution speleothem records. A variety of methods of trace element analysis are available, but standardization is a common problem with the most rapid methods. New stable isotope data on Irish stalagmite CC3 compares rapid laser-ablation techniques with the conventional analysis of micromilled powders and ion microprobe methods. A high degree of comparability between techniques ...

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“…are decay constants for 230 Th and 234 U, respectively, t is the time since the mineral formed and Th and U are the concentrations of the given Th or U isotope. Under oxidizing conditions typical of surface waters, U is mobile as the hexavalent uranlyl ion (U(VI)O 2 2+) and is readily incorporated into secondary minerals such as carbonates (Ku, 2000;Reeder et al, 2001). In contrast, Th is relatively insoluble under oxic conditions, and ideal samples have low initial Th concentrations such that all 230 Th is derived from radioactive decay of 234 U in the sample.…”

Section: Th-u Geochronologymentioning

confidence: 99%

An Assessment of Late Pleistocene to Middle Holocene Lake Level Fluctuations in Surprise Valley, California

Ibarra¹

2018

Preprint

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Knowledge of Earth’s climate history and sensitivity, combined with modeling past and future climate, are central to informing policy decisions regarding future climate change. The hydrologic response to future warming scenarios due to increased anthropogenic CO2 emissions remains uncertain. Freshwater availability in the arid western United States is projected to decrease in availability as increased agricultural, urban and industrial uses continue to stress supplies. Motivated by the potential for dramatic future hydrologic changes, studies recording the abrupt transitions between different equilibrium states of natural past climate variability shed light on our understanding of the modern climate system.The presence of pluvial lakes in the Basin and Range Province, in the western United States, during the late Pleistocene (40 to 10 ka) indicates far greater moisture availability during the Pleistocene glacials. This study investigates the timing and magnitude of the most recent pluvial lake cycle that filled Surprise Valley, California using geophysical, geochemical and geochronologic tools. Spanning 31.2 to 4.6 ka, this new lake level record places the highest lake level, at 180 meters above present day playa, at 13.9 ± 1.2 ka. This age appears to be nearly synchronous with highstands of Lake Lahontan to the south and the Chewaucan Basin to the north. Additionally, most of the Basin and Range lake highstands, including Lake Surprise, follow peaks in precipitation minus evapotranspiration (P-ET) by 8-10 kyr. By compiling a diverse set of paleoclimate data available for western North America, I found that the timing and geographic distribution of lake highstands is inconsistent with increased precipitation in response to shifting westerly winds, the current model for the genesis of large lakes in western North America. Rather, lakes levels are more strongly correlated with changes in summer insolation, suggesting that lake highstands were likely facilitated by colder temperatures and increased humidity due to the presence of continental ice sheets and increased atmospheric convergence. I compared the constraints from lake and soil-based records to Atmosphere-Ocean General Circulation Model simulations from the Paleoclimate Model Intercomparison Project 2. Based on model-proxy intercomparison, the Atmosphere-Ocean General Circulation Models, the same models used to also assess future climatic changes, poorly predict hydrologic quantities for the Last Glacial Maximum.

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Coprecipitation of Uranium(VI) with Calcite: XAFS, micro-XAS, and luminescence characterization

Cited by 193 publications

References 41 publications

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Modification and preservation of environmental signals in speleothems

An Assessment of Late Pleistocene to Middle Holocene Lake Level Fluctuations in Surprise Valley, California

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