Uranium in soil

Gueniot B, Munier-Lamy C, Berthelin J (1988b) Geochemical behavior of Uranium in soils, part 11 Distribution of uranium in hydromorphic soils and soil sequences. Application for suificial prospecting. J Geochem Explor 31 39-55... 

Moreira-Nordemann LM, Sieffermann G (1979) Distribution of uranium in soil profiles of Bahia state, Brazil. Soil Science 127 275-280... 

Bertsch, P. M., Hunter, D. B., Sutton, S. R., Bajt, S. Rivers, M. L. 1994. In situ chemical speciation of uranium in soils and sediments by micro x-ray absorption spectroscopy. Environmental Science and Technology, 28, 980-984. 

Toole et al. [225], Shaw and Francois [226] and Zbiral et al. [227] determined thorium (and uranium) in soils by inductively coupled plasma mass spectrometry. 

Parsa [228] has described a sequential radiochemical method for the determination of thorium (and uranium) in soils. Mukhtar et al. [229] have described a laser fluorometric method for the determination of thorium (and uranium) in soils. Steam digestion has been employed in the preparation of soil samples for the determination of thorium (and uranium) [230]. Thorium (and uranium) were determined by X-ray fluorescence using a germanium planar detector and by chemometric techniques. No sample preparation was required in this method [231]. 

Earlier methods for the determination of uranium in soils employed spectrophotometry of the chromophore produced with arsenic(III) at 655 nm [237 ] and neutron activation analysis [238]. More recently, laser fluorescence [239] and in situ laser ablation-inductively coupled plasma atomic emission spectrometry [240] have been employed to determine uranium in soil. D Silva et al. [241] compared the use of hydrogen chloride gas for the remote dissolution of uranium in soil with microwave digestion. 

An appreciable amount of work has been carried out on the application of microwave digestion techniques to the determination of heavy metals, arsenic and uranium in soils. 

Methods involving solutions in hydrogen chloride gas and microwave dissolution have been compared for the dissolution of uranium in soil [50]. 

Uranium deposited by wet or dry precipitation will be deposited on land or in surface waters. If land deposition occurs, the uranium can be reincorporated into soil, resuspended in the atmosphere (typically factors are around 10 ), washed from the land into surface water, incorporated into groundwater, or deposited on or adsorbed onto plant roots Gittle or none enters the plant through leaves or roots). Conditions that increase the rate of formation of soluble complexes and decrease the rate of sorption of labile uranium in soil and sediment enhance the mobility of uranium. Significant reactions of uranium in soil are formation of complexes with anions and hgands (e.g., COj, OH ) or humic acid, and reduction of U" " to U. Other factors that control the mobility of uranium in soil are the oxidation-reduction potential, the pH, and the sorbing characteristics of the sediments and soils (Allard et al. 1979, 1982 Brunskill and Wilkinson 1987 Herczeg et al. 1988 Premuzie et al. 1995). 

In addition to the migration of dissolved or suspended uranium due to the movement of water in the environment, the transport and dispersion of uranium in surface water and groundwater are affected by adsorption and desorption of the uranium on surface water sediments. On the other hand, migration of uranium in soil and subsoil and uptake in vegetation are usually quite local involving distances from several centimeters to several meters. 

The mobility of uranium in soil and its vertical transport (leaching) to groundwater depend on properties of the soil such as pH, oxidation-reduction potential, concentration of complexing anions, porosity of the soil, soil particle size, and sorption properties, as well as the amount of water available (Allard et al. 

Other factors also affect the mobility of uranium in soil. A field study performed near an active carbonate leach uranium mill showed that uranium in an alkali matrix can migrate to the groundwater (Dreesen et al. 1982). Uranium mobility may also be increased due to the formation of soluble complexes with chelating agents produced by microorganisms in the soil (Premuzie et al. 1995). 

The primary abiotic and biological processes that transform uranium in soil are oxidation-reduchon reactions that convert U(VI) (soluble) to U(IV) (insoluble). Reduction of U(VI) to U(IV) can occur as a result of microbial action under anaerobic soil or sediment conditions, thereby reducing the mobility of uranium in its matrix (Barnes and Cochran 1993 Francis et al. 1989). Further abiotic and biological processes that can transform uranium in the environment are the reactions that form complexes with inorganic and organic ligands (see Section 5.3.1). 

This reaction enhances the mobility of uranium in soil from mining and milling wastes (Barnes and Cochran 1993 de Siloniz et al. 1991 Scharer and Ibbotson 1982). 

The EPA developed two methods for the radiochemical analysis of uranium in soils, vegetation, ores, and biota, using the equipment described above. The first is a fusion method in which the sample is ashed, the silica volatilized, the sample fused with potassium fluoride and pyrosulphate, a tracer is added, and the uranium extracted with triisooctylamine, purified on an anion exchange column, coprecipitated with lanthanum, filtered, and prepared in a planchet. Individual uranium isotopes are separately quantified by high resolution alpha spectroscopy and the sample concentration calculated using the yield. The second is a nonfusion method in which the sample is ashed, the siUca volatilized, a tracer added, and the uranium extracted with triisooctylamine, stripped with nitric acid, co-precipitated with lanthanum, transferred to a planchet, and analyzed in the same way by high resolution a-spectroscopy (EPA 1984). 

METHODS AND RESULTS 2.1 Uranium in soil for spinach cultivation... 

Bertsch PM, Hunter DB, Sutton SR, Bajt S, Rivers ML (1994) In situ chemical speciation of uranium in soils and sediments by micro X-ray absorption spectroscopy. Environ Sci Technol 28 980-984 Bertsch PM and Seaman JC (1999) Characterization of complex mineral assemblages Implications for contaminant transport and environmental remediation. Proc Nat Acad Sci USA 96 3350-3357 Beyersmann D, Koester A, Buttner B, Flessel P (1984) Model reactions of chromium compounds with mammalian and bacterial cells. Toxicol Environ Chem 8 279-286 Bhattachaiya P, Chatterjee D, Jacks G (1997) Occurrence of arsenic contaminated groundwater in alluvial aquifers from Delta Plains, Eastern India Options for safe drinking water supply. Int Jour Water Resources Management 13 79-92... 

Radiation is a tbrm of energy. It comes from man-made sources. such as x-ray machines, from the sun and outer space, and from some radioactive materials such as uranium in soil. 

Papachristodoulou CA, Assimakopoulos PA, Patronis NE, loannides KG (2003) Use of HPGe (-ray spectrometry to assess the isotopic composition of uranium in soils. J Environ Radioact 64 195-203... 

Several attempts have been made in order to correlate the values to physico-chemical properties of soils however, not much success has been accomplished. Carlon et al. [26] reported a correlation between pH and soil-water distribution coefficient (K ) for Pb log = 1.99-1- 0.42pH. The EPA [19] collected values for cadmium, cesium, chromium, lead, plutonium, radon, strontium, thorium, tritium and uranium in soils. The variability in values can be many orders of magnitude as shown in Table 2. 

The alpha activity of uranium in soil samples from Slovakia was determined after a relatively simple sample preparation procedure (Donoval and Matel 2001). The soil samples were dried, ground, and ashed at 550°C, leached with HNO3 + HCl and HNO3 + HF. This was followed by solvent extraction, chromatographic separation of uranium from thorium, deposition with NdFj and alpha spectroscopy for the determination of the 238U/234U ratio. 

FIGURE 3.7 Schematic presentation of the stages for the determination of uranium in soil... 

Determination of uranium in soil samples can be carried out by nondestructive analysis (NDA) methods that do not require separation of uranium (needed for alpha spectrometry or TIMS) or even digestion of the soil for analysis by ICPMS, ICPAES, or some other spectroscopic methods. These NDA methods can be divided into passive techniques that utilize the natural radioactive mission (gamma and x-ray) of the uranium and progeny radionuclides or active methods where neutrons or electromagnetic radiation are used to excite the uranium and the resultant emissions (gamma, x-rays, or neutrons) are monitored. In many cases, sample preparation is simpler for these nondestructive methods but the requiranent of a neutron source (from a nuclear reactor in many cases) or a radioactive source (x-ray or gamma) and relatively complex calibration and data interpretation procedures make the use of these techniques competitive only in some applications. In addition, the detection limits are usually inferior to the mass spectrometric techniques and the isotopic composition is not readily obtainable. 

Wise (2012, October 15). Uranium in soil and building material—Individual dose calculator. Retrieved March 2, 2014, from http //www.wise-uranium.org/rdcush.html. 

Smith A. Y. and Lynch J. J. Field and laboratory methods used by the Geological Survey of Canada in geochemical surveys no. 11. Uranium in soil, stream sediment and water. Pap. geol. Surv. Can. 69-40, 1969, 9 p. 

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