Begy R-Cs, Simon H, Kelemen Sz, Preoteasa L
Babeș-Bolyai University, Faculty of Environmental Science and Engineering, Fântânele 30, 400294, Cluj-Napoca, Romania; Babeș-Bolyai University, Interdisciplinary Research Institute on Bio-Nano-Science, Treboniu Laurean 42, 400271, Cluj-Napoca, Romania.
Babeș-Bolyai University, Faculty of Environmental Science and Engineering, Fântânele 30, 400294, Cluj-Napoca, Romania.
J Environ Radioact. 2018 Dec;192:95-104. doi: 10.1016/j.jenvrad.2018.06.010. Epub 2018 Jun 15.
Being a dynamic environment associated with complex costal, fluvial and marine processes, only a few studies regarding the evolution of the Danube Delta and the human impacts on its ecosystem have been carried out. Being a sensible to all processes occurring in its catchment area, information is stored in the deposited sediments, which can be used as tracers for natural and anthropogenic processes. The aim of this study is to determine a detailed reconstruction of the sedimentation rates in the last century by applying the Pb dating method validated by Cs profiles. Additionally, the impacts of the construction of river-regulating structures (mainly the Iron Gates Hydro-Energetic Power Plants) are investigated, along with the assessment of natural phenomena (floods, storms etc.). To achieve this, 26 sediment cores from seven lakes were collected. Pb and Cs were determined using gamma spectrometry, while Pb was measured via alpha spectrometry (Po), using the CRS model for age determination. From the assessed lakes, the most affected was the Matița Lake with a maximum sedimentation rate of 10.93 g cm yr and the least affected was the Isac Lake. Average sedimentation rates are: 0.95 g cm yr for Cruhlig Lake, 0.70 g cm yr for Uzlina Lake, 0.44 g cm yr for Isac Lake, 0.47 g cm yr for Cuibida Lake, 0.51 g cm yr for Iacob Lake, 1.00 g cm yr for Matița Lake and 0.76 g cm yr for Merhei Lake. Physical parameters (water content, porosity and bulk density) and LOI (organic matter and inorganic carbon content) were determined for each core to differentiate organic and non-organic sedimentation. Beside the natural influences, it is difficult to track the effects of the Iron Gates and not all analysed lakes were suitable for this task. The 1940-1970 period and the following ten years were compared in means of sedimentation: a decrease in sedimentation can be observed in four of the lakes: 59% in Cruhlig Lake, 16% in Uzlina Lake, 10% in Iacob Lake and 42% in Isac Lake, leading to an average 32% for the four lakes. The other three lakes show increasing tendencies of 39% in this period: 87% in Matița Lake, 6% in Merhei Lake and 24% in Cuibida Lake. Sedimentation rates show growths of 3 times after 1989, the most affected being the two northern lakes (3 times increase in both Matița Lake and Merhei Lake) and the four central lakes (2 times in case of Cuibida Lake, 3 times in Iacob Lake, 3 times in Isac Lake and 4 times in Uzlina Lake) with an average increase of 3 times, while the southern one (Cruhlig Lake) 2 times.
多瑙河三角洲是一个与复杂的海岸、河流和海洋过程相关的动态环境，关于多瑙河三角洲的演变以及人类对其生态系统影响的研究开展得较少。由于对其集水区内发生的所有过程都很敏感，相关信息存储在沉积的沉积物中，这些沉积物可作为自然和人为过程的示踪剂。本研究的目的是通过应用经铯剖面验证的铅测年方法，详细重建上个世纪的沉积速率。此外，还研究了河流调节结构（主要是铁门水力发电厂）建设的影响，并评估了自然现象（洪水、风暴等）。为实现这一目标，从七个湖泊采集了26个沉积物岩芯。使用伽马能谱法测定铅和铯，同时通过α能谱法（钋）测量铅，并使用CRS模型进行年龄测定。在所评估的湖泊中，受影响最大的是马蒂察湖，最大沉积速率为10.93克/平方厘米·年，受影响最小的是伊萨克湖。平均沉积速率分别为：克鲁赫利格湖0.95克/平方厘米·年，乌兹利纳湖0.70克/平方厘米·年，伊萨克湖0.44克/平方厘米·年，库比达湖0.47克/平方厘米·年，雅各布湖0.51克/平方厘米·年，马蒂察湖1.00克/平方厘米·年，梅尔黑湖0.76克/平方厘米·年。测定了每个岩芯的物理参数（含水量、孔隙率和 bulk密度）和烧失量（有机质和无机碳含量），以区分有机和无机沉积。除了自然影响外，很难追踪铁门的影响，并非所有分析的湖泊都适合这项任务。对1940 - 1970年期间及随后十年的沉积情况进行了比较：在四个湖泊中观察到沉积减少：克鲁赫利格湖减少59%，乌兹利纳湖减少16%，雅各布湖减少10%，伊萨克湖减少42%，四个湖泊平均减少32%。其他三个湖泊在此期间呈现增长趋势，增长了39%：马蒂察湖增长87%，梅尔黑湖增长6%，库比达湖增长24%。1989年后沉积速率增长了3倍，受影响最大的是北部的两个湖泊（马蒂察湖和梅尔黑湖均增长3倍）以及中部的四个湖泊（库比达湖增长2倍，雅各布湖增长3倍，伊萨克湖增长3倍，乌兹利纳湖增长4倍），平均增长3倍，而南部的克鲁赫利格湖增长2倍。
