Activity concentrations of radionuclides in 5 short cores taken in 2007-2008 measured by ICP-MS and HPGe gamma spectrometry

Natural radionuclides and man-made 137Cs were analyzed in five short sediment cores taken in northern part of the Gulf of Eilat (Gulf of Aqaba) in order to provide information on sedimentation and mixing rates and sediment sources. The maximum estimates of sedimentation rates based on excess 210Pb were found to vary between 0.105 ± 0.020 and 0.35 ± 0.23 cm · year**-1. Even the lowest estimates are significantly higher than those expected from dust deposition, suggesting other sources and processes being responsible for most of the allochthonous material accumulation, including periodical floods following heavy rain events, internal erosion or triggers, like earthquakes. In 137Cs depth profiles no 1963 related nuclear weapon test maxima were found; instead, the activities decrease monotonically, suggesting that a major process leading to radionuclides' depth distribution might be mixing. The mixing rates calculated from 137Cs, excess 210Pb and excess 228Th reach values up to 2.18 ± 0.69 cm**2 · year**-1.为获取埃拉特湾（亚喀巴湾）北部采集的5根短沉积岩芯的沉积速率、混合速率及沉积物来源相关信息，本研究对其中的天然放射性核素（natural radionuclides）与人工放射性铯-137（¹³⁷Cs）开展了分析。基于过剩铅-210（excess ²¹⁰Pb）估算的沉积速率最大值区间为0.105 ± 0.020至0.35 ± 0.23 cm·年⁻¹。即便最低估算值也显著高于粉尘沉积的理论预期值，表明绝大多数外来沉积物的堆积主要由其他过程与来源主导，包括强降雨事件引发的周期性洪水、内部侵蚀或地震等触发因素。在¹³⁷Cs的深度剖面中未发现与1963年核武器试验相关的活度峰值；取而代之的是放射性活度随深度单调递减，这暗示控制放射性核素深度分布的主要过程为沉积物混合。基于¹³⁷Cs、过剩铅-210（excess ²¹⁰Pb）及过剩钍-228（excess ²²⁸Th）计算得到的混合速率最高可达2.18 ± 0.69 cm²·年⁻¹。