Siddeeg Saifeldin M, Bryan Nicholas D, Livens Francis R
Centre for Radiochemistry Research, School of Chemistry, The University of Manchester, Manchester, M13 9PL, UK.
Environ Sci Process Impacts. 2015 Jan;17(1):235-45. doi: 10.1039/c4em00230j. Epub 2014 Dec 12.
Sediment samples were collected from the vicinity of the abandoned South Terras uranium mine in south-west UK and analysed for uranium and (226)Ra to explore their geochemical dispersion. The radioactivity concentrations in the sediment samples were measured using alpha spectrometry for uranium, and gamma spectrometry for radium. Sequential chemical extraction was applied to selected sediments in order to investigate the speciation of the radionuclides and their association with stable elements. The activity ratio of the uranium isotopes was used to explore the mobility of uranium, and scanning electron microscopy (SEM) and electron microprobe analysis (EMPA) were used to characterise the sediments. The radiochemical results identified two locations with enhanced radioactivity, so two samples from these locations were further investigated. The geochemical distribution of the radionuclides in these two samples varies within the five operationally-defined fractions. In one sample, the majority of the uranium was released from the 'carbonate' fraction, followed by the organic fractions. Similarly, in the second sample, the uranium was mainly resealed from the carbonate fraction, although a considerable percentage associated with the resistant fraction. The fractionation trend of radium noticed to show some similarities to that of barium, as expected from the similarity in their chemistries. Geochemical distributions of the stable elements, such as Mn, Ti and As, were different in the enhanced radioactivity samples. The activity ratio of (234)U/(238)U shows different trends in the two sediments, signifying the impact of organic matter and/or the exchange between water and sediment. SEM and EMPA analysis identified uranium-bearing phases in association with potassium, calcium, iron, manganese and arsenic.
从英国西南部废弃的南特拉什铀矿附近采集了沉积物样本，并对其进行铀和镭 - 226分析，以探索它们的地球化学扩散情况。使用α能谱法测量沉积物样本中的铀放射性浓度，使用γ能谱法测量镭的放射性浓度。对选定的沉积物进行顺序化学萃取，以研究放射性核素的形态及其与稳定元素的关联。利用铀同位素的活度比来探索铀的迁移性，并使用扫描电子显微镜（SEM）和电子微探针分析（EMPA）对沉积物进行表征。放射化学结果确定了两个放射性增强的位置，因此对来自这些位置的两个样本进行了进一步研究。这两个样本中放射性核素的地球化学分布在五个操作定义的组分中有所不同。在一个样本中，大部分铀从“碳酸盐”组分中释放出来，其次是有机组分。同样，在第二个样本中，铀主要从碳酸盐组分中重新封闭，尽管有相当比例与抗性组分相关联。镭的分馏趋势与钡的分馏趋势有一些相似之处，这与它们化学性质的相似性预期一致。在放射性增强的样本中，稳定元素如锰、钛和砷的地球化学分布不同。（234）U/（238）U的活度比在两种沉积物中呈现不同趋势，这表明了有机物和/或水与沉积物之间交换的影响。SEM和EMPA分析确定了与钾、钙、铁、锰和砷相关的含铀相。
