Pedersen Jørn B T, Bartholdy Jesper, Christiansen Christian
Department of Geography, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
J Environ Radioact. 2007;97(1):42-56. doi: 10.1016/j.jenvrad.2007.03.002. Epub 2007 Apr 20.
The 137Cs activity of salt marsh and tidal flat sediments of the northern part of the European Wadden Sea was studied based on a comprehensive dataset of 210Pb dated cores. The 137Cs inventory of salt marsh sediments shows a major peak corresponding to the Chernobyl accident in 1986, and a minor peak located in the late 1960s interpreted as the combined effect of atmospheric testing of nuclear weapons. Emissions from the nuclear reprocessing plant Sellafield are not reflected as peaks in 137Cs activity, but may contribute to the rising 137Cs activity in the years prior to 1986. The 137Cs activity of tidal flat sediments differs from salt marsh sediment in two respects. First, the activity is much lower and, second, the major peak in the 1980s is located in the beginning instead of in the middle of the decade. The differences in 137Cs inventory between the two environments are interpreted to result from repeated cycles of deposition/resuspension and mixing on tidal flats. A simple model illustrating the consequence of mixings returns an apparent shift of major peaks in 137Cs activities backwards in time corresponding to the mixing depth divided by the deposition rate.
基于210Pb测年岩芯的综合数据集，对欧洲瓦登海北部盐沼和潮滩沉积物中的137Cs活度进行了研究。盐沼沉积物的137Cs存量显示出一个与1986年切尔诺贝利事故相对应的主要峰值，以及一个位于20世纪60年代末的次要峰值，该次要峰值被解释为核武器大气试验的综合影响。核后处理厂塞拉菲尔德的排放并未在137Cs活度中体现为峰值，但可能导致了1986年之前137Cs活度的上升。潮滩沉积物的137Cs活度在两个方面与盐沼沉积物不同。第一，活度要低得多；第二，20世纪80年代的主要峰值位于该年代初期而非中期。两种环境中137Cs存量的差异被解释为潮滩上沉积/再悬浮和混合的反复循环所致。一个说明混合后果的简单模型显示，137Cs活度主要峰值在时间上向后的明显偏移与混合深度除以沉积速率相对应。
