Sediment Records of Fallout Radionuclides and their Application to Studies of Sediment-Water Interactions
Sediment Records of Fallout Radionuclides and their Application to Studies of Sediment-Water Interactions
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DOI：
10.1007/978-94-011-5552-6_58
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发表时间：
1997-10
期刊：
影响因子：
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通讯作者：
P. Appleby
中科院分区：
文献类型：
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作者：
P. Appleby
沉降物中的放射性核素210 Pb和137 Cs被广泛用于湖泊沉积物中环境记录的定年。由于放射性核素记录本身是大气沉降物转化的结果，它通过介导从集水区通过水柱和沉积后经由孔隙沃茨迁移的迁移过程，因此这些过程的可靠模型对于准确测年至关重要。湖泊沉积物中~（210）Pb和~（137）Cs的大量测年数据可用于迁移模型的研究。它们作为迁移过程示踪剂的优点包括通过环境的广泛扩散、相对简单和众所周知的输入函数以及易于测量。控制任何物种通过水柱迁移的主要因素之一是其在水相和颗粒相之间的分布。沉积物中137 Cs、210 Pb的存量比低于直接沉降物的预期值，证明了137 Cs在水柱中的相对溶解度。利用坎布里亚湖的大量沉积物记录，基于简单模型的计算表明，水柱中武器沉降物137 Cs的颗粒分数在5- 22%之间，与沉积速率（由210 Pb确定）的平方根成正比。武器137 Cs在水柱中的KD值估计在1-2× 105 L kg−1之间。这与直接测量这些湖泊中铯-137的Kd值（Smithet al.in press）相当。
The fallout radionuclides210Pb and137Cs are widely used to date environmental records contained in lake sediments. Since the radionuclide records are themselves the outcome of the transformation of atmospheric fallout by mediating transport processes from the catchment, through the water column and post-depositional migration via pore waters, reliable models of these processes are crucial to accurate dating. The large quantities of data on210Pb and137Cs in lake sediments accumulated through their widespread dating applications may be used to study transport models. Their advantages as tracers of transport processes include widespread dispersal through the environment, relatively simple and well known input functions, and ease of measurement.One of the principle factors controlling the transport of any species through the water column is its distribution between aqueous and particulate phases. The relatively solubility of137Cs in the water column is demonstrated by the reduced137Cs,210Pb inventory ratios in sediments compared to values expected from direct fallout. Using sediment records from a wide range of Cumbrian lakes, calculations based on simple models indicate that the particulate fraction of weapons fallout137Cs in the water column ranged from 5–22%, and was proportional to the square root of the sedimentation rate (determined by210Pb). TheKDvalue for weapons137Cs in the water column is estimated to be in the range 1–2×105L kg−1. This is comparable withKDvalues for Chernobyl137Cs in these lakes (Smithet al.in press) obtained from direct measurements in the cater column.