Age and isotopes in bottom sediments from Core VER-99-1-St2, Baikal Lake

A simple, reliable, and efficient method has been elaborated for direct determination of isotopic composition of authigenic uranium in siliceous lacustrine sediments. The method is based on studying kinetics of selective extraction of authigenic uranium from sediments by weak solutions of ammonium hydrocarbonate followed by ICP-MS analysis of nuclides. To estimate contamination of authigenic uranium by terrigenous one contents of 232Th and some other clastogenic elements in the extracts were measured simultaneously. Selectivity of extraction of authigenic uranium from the sediments treated with 1% NH4HCO3 solution appeared to be no worse than 99%. The method was applied to analysis of isotopic composition of authigenic uranium at several key horizons of the earlier dated core from the Baikal Lake. Measurements directly show that 234U/238U values in Baikal water varied depending on climate, which contradicts existing hypotheses. Measured 234U/238U ratios in water of the paleo-Baikal match corresponding values reconstructed from isotopic data for total uranium in the sediments on supposition that U/Th ratio is constant in terrigenous fraction of the sediments. Direct experimental determination of total and authigenic nuclides in sediments enhances potentiality of the method for 234U-230Th dating of non-carbonate lacustrine sediments including those from the Baikal Lake within intervals corresponding to periods of glaciation, when sediments were rich in terrigenous components. Portions of terrigenous and authigenic uranium are well separated and we can study variability of sources of terrigenous matter and refine the earlier model for reconstructing climate humidity in the East Siberia.

Environmental Monitoring and Support Laboratory : Las Vegas, Nevada.

Mode of access: Internet.

Ecological studies of fish near a coal-fired generating station and related laboratory studies : Wisconsin power plant impact study /

"Grant no. R803971."

Materials Science and Engineering Laboratory.

"December 1993"--P. [2] of cover.

Research report - Corps of Engineers, U.S. Army, Cold Regions Research and Engineering Laboratory.

Some no. issued in more than one part.

Physics 117 and 118; laboratory instructions and supplementary problems.

Mode of access: Internet.

Suggested plan for organization and operation. Laboratory course in inspection practice for aircraft manufacture.

Unites A-B-C.

Manual of dehydrated culture media and reagants for microbiological and clinical laboratory procedures.

Mode of access: Internet.

Minimum standards for the commercial production of random bred and inbred laboratory mice (rev. Sept., 22, 1957)

Reprinted from the Journal of the National Cancer Institute, vol. 19, no. 6, Dec. 1957.

Factors affecting the nutritive value of foods : studies at the U.S. Plant, Soil, and Nutrition Laboratory.

"Issued December 1948."

Collected reprints - Atmospheric Physics and Chemistry Laboratory.

Includes bibliographical references.