[en] Dried, sized, and homogenized peat that contained 5980 ± 307 ppm U was subjected to a variety of leaching conditions to determine the nature and strength of U-organic bonding in recently accumulated organic matter. The fraction of U leached in 24 h experiments at 25⁰C ranged from 0 to 95%. The most effective leach solutions included H₂SO₄ and concentrated (>0.01 M) solutions of sodium bicarbonate-carbonate, or sodium pyrophosphate. Effective leaching by carbonate and pyrophosphate in the absence of added oxidant, and the insignificant effect of added oxidant (as pressurized O₂) strongly suggest that U is initially fixed on organic matter as an oxidized U(VI) species. Uranium is more strongly bound than some other polyvalent cations, based on its resistance to exchange in the presence of large excesses of dissolved Ca²⁺ and Cu²⁺. Measurements of the rate of U leaching indicate faster rates in acid solution compared to carbonate solution, and are consistent with simultaneous attack of sites with different affinities for U. Sulfuric acid appears a good choice for commercial extraction of U from mined peat. In situ disturbances such as overliming of peat soils, addition of fertilizers containing pyrophosphate, or incursions of natural carbonate-rich waters could produce significant remobilization of U, and possibly compromise the quality of local domestic water supplies. (author)

[en] A method of analysis of geological materials for the determination of the rare-earth elements using the inductively coupled plasma mass spectrometric technique (ICP-MS) has been developed. Instrumental parameters and factors affecting analytical results have been first studied and then optimized. Samples are analyzed directly following an acid digestion, without the need for separation or preconcentration with limits of detection of 2-11 ng/g, precision of +/-2.5% relative standard deviation, and accuracy comparable to inductively coupled plasma emission spectrometry and instrumental neutron activation analysis. A commercially available ICP-MS instrument is used with modifications to the sample introduction system, torch, and sampler orifice to reduce the effects of high salt content of sample solutions prepared from geologic materials. Corrections for isobaric interferences from oxide ions and other diatomic and triatomic ions are made mathematically. Special internal standard procedures are used to compensate for drift in metal:metal oxide ratios and sensitivity. Reference standard values are used to verify the accuracy and utility of the method

[en] Previously reported concentrations of U in well and surface waters of the Arkansas River drainage in southeastern Colorado approach or exceed the proposed EPA drinking water standard of 20 ppb U with values as high as 230 ppb. The authors sampled water, solid and bedrock in the drainage to determine the influence of natural weathering and agricultural practices on the amount of dissolved U. Waters are of the Na-Ca-SO₄ type and are saturated with gypsum and calcite. Dissolved U correlates positively with conductivity and occurs as uranyl carbonate complexes. In nonirrigated areas U is dissolved during oxidative chemical weathering of sulfidic marine shales (U=2-12 ppm) and their derivative soils, and can be concentrated to as much as 100 ppb in ponded surface water and shallow ground water. Irrigation increase the rate of natural weathering and enhances soil-water contact as irrigation waters return to the river and the alluvial aquifer for reuse downstream. In irrigated areas limited application of phosphate-bearing fertilizer containing as much as 150,000 ppb U also may contribute some uranium to local waters