Department of Quaternary Geology and Paleogeography, Adam Mickiewicz University, Dziegielowa 27, 61-680 Poznań, Poland.
Department of Radioisotopes, Institute of Physics, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland.
J Environ Radioact. 2017 Apr;169-170:174-185. doi: 10.1016/j.jenvrad.2017.01.015. Epub 2017 Jan 23.
In this study we combined radioisotopes (Pb, Cs and Be) and hydrodynamic modeling to investigate sedimentary processes in three coastal lakes on the Polish Baltic coast. The research aimed at establishing the depth of sediment mixing and its effects on sediment geochemistry as well as showing the relationship between lake water salinity and radionuclide distribution in the sediment cores. We established that the intensity of mixing displayed appreciable variability throughout the lakes and the thickness of sediment mixing layer was between <2 and 22 cm. The mixing was primarily due to wind-induced waves. The vertical mixing was shown to shift sulfidation of the sediments towards deeper layers. We found that the distributions of radioisotopes, Cs in particular, in the sediment cores from coastal lakes were strongly affected by the early diagenetic processes, which caused diffusive migration of radionuclides. The inventories of Pb and Cs in the lakes were positively related to salinity. The high inventories of both isotopes (3.2-10.9 kBq ·m for Pb and 3.0-6.0 kBq·m for Cs) in coastal lakes were explained by enhanced sedimentation within estuarine mixing zone and delivery of "additional" Pb and Cs to the lakes during saltwater ingressions. The results of this study have implications for the paleolimnology, sedimentology and biogeochemistry of coastal lakes.
在这项研究中，我们结合放射性同位素（Pb、Cs 和 Be）和水动力模型来研究波兰波罗的海沿岸三个沿海湖泊的沉积过程。该研究旨在确定沉积混合的深度及其对沉积地球化学的影响，并展示湖泊水盐度与沉积核心中放射性核素分布之间的关系。我们确定，混合强度在整个湖泊中表现出相当大的可变性，沉积混合层的厚度在<2 到 22 cm 之间。混合主要是由风引起的波浪造成的。垂直混合表明沉积物的硫化作用向更深的层迁移。我们发现，沿海湖泊沉积核心中放射性同位素的分布，特别是 Cs 的分布，受到早期成岩作用的强烈影响，这导致了放射性核素的扩散迁移。湖泊中 Pb 和 Cs 的储量与盐度呈正相关。沿海湖泊中两种同位素（Pb 为 3.2-10.9 kBq·m，Cs 为 3.0-6.0 kBq·m）的高储量归因于河口混合区的沉降增强，以及盐水入侵期间向湖泊输送“额外”的 Pb 和 Cs。本研究结果对沿海湖泊的古湖沼学、沉积学和生物地球化学具有重要意义。
