Konstantinova Marina, Prokopčuk Nina, Tarasiuk Nikolaj
Center for Physical Sciences and Technology, Savanorių 231, LT-02300, Vilnius, Lithuania.
Vilnius University, Faculty of Medicine, Antakalnio Str.57, Vilnius, LT-10207, Lithuania.
J Environ Radioact. 2023 Jun;262:107150. doi: 10.1016/j.jenvrad.2023.107150. Epub 2023 Mar 17.
The shapes of the deep slope (below the maximum values) of the vertical profiles of radiocesium activity concentrations in the sediment samples taken in 2003-2012 in the Lakes Juodis, Tapeliai and Red lake were studied. The Gaussian shape of the deep slope indicates the migration of radiocesium into the depths of the sediments, and this process is significantly enhanced in some places due to bioturbation caused by tench preparing for hibernation. The exponential shape of the deep slope is typical for sediments in which in winter, in the presence of an ice cover on the lake, thermodynamic mixing occurs in the surface layer caused by the effects of pore water buoyancy. In these sediments, radiocesium dissolved in the pore fluid migrates upwards into the near-bottom water, becoming a source of secondary pollution of the water column. In winter, the presence of such a process is easily determined by the emergence of a layered structure of the water column in the lake and the temperatures of the near-bottom waters exceeding 4 °C. In this case, each layer is characterized by constant standard water parameters (temperature, conductivity, concentrations of oxygen, and trace elements). Complex forms of the deep slope of the vertical profile of radiocesium activity concentrations, combining elements of the exponential and Gaussian forms, indicate the episodic presence of both migration mechanisms. A method is proposed for identifying sediments that are a source of secondary pollution of lake waters by estimating the differences between the normalized logarithms of the radiocesium activity concentrations of the deep slopes (below the maximum concentrations) of its vertical profiles in the sediments of the studied samples and the sample of the carbonate barrier sediments, which were discovered in the shallow part of Lake Juodis in 2003.
研究了2003 - 2012年在尤迪斯湖、塔佩利亚伊湖和红湖采集的沉积物样本中放射性铯活度浓度垂直剖面深斜率（低于最大值）的形状。深斜率的高斯形状表明放射性铯向沉积物深处迁移，并且由于丁鱥准备冬眠引起的生物扰动，这一过程在某些地方显著增强。深斜率的指数形状是冬季湖面上有冰盖时，表层因孔隙水浮力作用发生热力混合的沉积物所特有的。在这些沉积物中，溶解在孔隙流体中的放射性铯向上迁移到近底层水体中，成为水柱二次污染的来源。在冬季，通过湖泊水柱分层结构的出现以及近底层水温超过4℃，很容易确定这种过程的存在。在这种情况下，每一层都具有恒定的标准水参数（温度、电导率、氧气浓度和微量元素）。放射性铯活度浓度垂直剖面深斜率的复杂形式，结合了指数和高斯形式的元素，表明两种迁移机制偶尔都会出现。提出了一种方法，通过估计研究样本沉积物垂直剖面深斜率（低于最大浓度）的放射性铯活度浓度归一化对数与2003年在尤迪斯湖浅水区发现的碳酸盐屏障沉积物样本之间的差异，来识别作为湖水二次污染源的沉积物。
