Studies on Ra, U, Th and Minor Element Contents in DVDP Cores and Deposits from Vestfold Hills

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The ignition loss and the Ra contents in the 10% HClO_4-soluble fraction and Na_2CO_3-fusion fraction were respectively determined for the DVDP 13 and 14 cores and four lake deposits in the Vestfold Hills. The powdered sample dried at 110℃ to constant weight, was weighed, added with 10% HClO_4 solution, then heated on a water bath and filtered. The filtrate is called the HClO_4-soluble fraction. The residue was fused with sodium carbonate. The fused mass was leached with water and HCl, which is called the Na_2CO_3-fusion fraction. Radium in each fraction was separated by coprecipitation with barium sulfate. It was then left standing in a Curie's bottle for a month. Determination of Ra was carried out with a liquid scintillation counter by measuring the activity of Rn in the radioactive equilibrium. The other radioactive elements such as U and Th and other minor elements were determined in the same samples. The U content was obtained by the fluorometry and the Th content by the colorimetry of thorin after separation of some interfering ions with cation exchange resins. For minor elements, the nondestructive neutron activation method was employed and 23 elements were determined by irradiating the samples with the reactor (TRIGA Mark II) at St. Paul's University, followed by the γ-ray spectrometry with a multichannels pulse height analyzer. Some of the results are shown in Tables. Discussion will be based upon these data.
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