陇东高原全新世黄土古土壤沉积序列辐射环境研究

The Natural Dose-rate of Holocene Loess-soil Sequences in Eastern Gansu Plateau in China

通过对泾河上游陇东高原两个全新世黄土古土壤沉积序列剂量率的分析,发现全新世剖面中剂量率值的变化分别受到了沉积粉尘物质组成的变化和易淋溶元素迁移的影响。前者对剂量率的影响非常微弱;后者的影响相对较大。同时剖面内部剂量率的绝对值变化较小。Fe/Al值的变化也表明了整个全新世黄土古土壤剖面中沉积粉尘的物质组成变化极小,指示了研究区域沉积物源在全新世近万年时间尺度内是相对较稳定的。

Nuclear radiation is emitted when a nucleus undergoes radioactive decay from radio elements,such as potassium,thorium,and uranium.So loess and soil are mainly the dust of exposure to the nuclear radiation in Holocene loess-soil sequences.In this paper,two Holocene loess-soil sequences on the Loess Plateau of China are used to explore the variation of natural dose-rate.The concentrations of the radioactive elements were determined by X-ray fluorescence spectrometry.The natural dose-rate can be calculated using the method of fine-grain dating that was described by Aitken in 1998.The distribution of natural dose-rates can be estimated in this paper.The analytical results indicated that dose-rate was influenced by the chemical composition of dust deposits and climate （especially rainfall）.The dose-rate also had a famous transition over the borderline of Lt/S0,or the borderline of S0/L0.However,the standard deviation is very small.The influence of the chemical composition of dust deposits on dose-rate is weak,as compared to climate and eluviations of Ca,and Na.In Holocene loess-soil sequences,the transformation of chemical composition is of feebleness,especially in the layer that stands for climate change.This indicated that the system of wind in Holocene showed weak transformation.So the pedogenesis had priority as compared with the chemical composition of deposition.