Radionuclides in ice cores I and II from Vernagferner, Austria

Fission product (90Sr-90Y, 137Cs, total beta) and 21OPb-210Po activities were measured in core samples from the temperate vernagtferner (3150 m altitude, Oetztal Alps, Austria). The results show that the investigated fission products are transported with water resulting from melting processes, and are sorbed on dust or dirt horizons. These products are, therefore, not suited for dating temperate glaciers. 210Pb is also transported with water and displaced from its original deposition. However, despite large fluctuations, the specific activity of 210Pb decreases with depth, and can be used to estimate accumulation rates and the age of the ice. The average annual accumulation rate amounts to about 80 cm water equivalent, and the deepest sample (81 m i.e. ab. 65 m w. e.) was deposited in the beginning of this century. These results agree with data obtained from other observations on this glacier and show that the 210Pb_method is suitable to date temperate glaciers, if the ice cores cover a time interval of about 100 years (i.e. ab. 4 half-lives of 210Pb). The surface activity of 210Pb was found to be 5 ± 1 dpm per kg of ice in agreement with other locations in the Alps and with measurements of fresh snow.对奥地利厄茨塔尔阿尔卑斯山脉（海拔3150米）的温带冰川凡尔纳特费纳（Vernagtferner）的冰芯样品，测定了裂变产物（Fission product，涵盖⁹⁰Sr-⁹⁰Y、¹³⁷Cs与总β放射性）以及²¹⁰Pb-²¹⁰Po的活度。研究结果表明，所考察的裂变产物随融冻过程产生的水体迁移，并吸附于尘埃或污垢地层中。因此，这类裂变产物不适用于温带冰川的年代测定。 ²¹⁰Pb同样随水迁移，并脱离其初始沉积位置。尽管存在较大波动，²¹⁰Pb的比活度随深度呈递减趋势，可用于估算冰的积累速率与冰体年龄。该冰川的年平均积累量约为80厘米水当量，最深样品（81米，即约65米水当量）沉积于本世纪初。本研究结果与该冰川其他观测所获数据一致，表明若冰芯覆盖约100年的时间跨度（即约²¹⁰Pb的4个半衰期），则²¹⁰Pb法适用于温带冰川的年代测定。测得的²¹⁰Pb表面活度为5±1 dpm每千克冰，该结果与阿尔卑斯山区其他点位以及新鲜积雪的测量结果相符。