バイカル湖堆積物の元素組成特性とその鉛直変動から見た古環境(平成17年度京大原子炉実験所専門研究会要旨)

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Thirty-one short sediment cores (20-50 cm in length) and two long drilling cores (BDP93-2 and BDP96-1; ca. 100 m and 200 m in length, respectively) from Lake Baikal were analyzed for about 40 elements by inductively coupled plasma atomic emission spectrometry and instrumental neutron activation analysis. The L. Baikal sediment was rich in Na, alkaline earth elements, U, and rare earth (especially light rare earth) elements, but deficient in Cs and Br. Fe-Mn-rich oxidized sediment layers, occurred sometimes as crust, contained high concentrations of Ba, Co, Ni, As, and P, among which cationic elements were in the Mn- oxide phase and anionic elements in the Fe-oxide phase. The surface sediment has been slightly polluted with Pb. Ratios of light rare earth elements/heavy rare earth elements in the sediment decreased from northern to southern parts of the lake. Climate changes induced by Milankovitch cycles have been recorded in elemental compositions of the drilling cores. Among the elements analyzed, U was the most sensitive climate indicator.