豫中黄土地区全新世黄土古土壤沉积序列辐射环境研究

选取豫中黄土地区典型的黄土古土壤沉积序列,根据其沉积物中U、Th、K元素的浓度及沉积序列所在地的纬度、经度、海拔对宇宙射线的影响,计算了沉积序列中环境辐射的强度。结果表明:黄土古土壤剖面的平均辐射强度为19.86mGy a-1,变化幅度在21%左右。环境辐射强度在S0、Lt、L1层位中较大,均值分别为20.58、23.19、22.47 mGy a-1。在TS层沉积物中辐射强度最小,平均剂量率为11.35mGy a-1。剂量率值在全新世剖面中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。前者对剂量率变化的影响非常微弱;后者的影响则相对较大。Fe/Al值的变化也说明了整个黄土古土壤沉积序列在全新世期间沉积粉尘的物质组成变化非常微弱,指示了全新世近万年尺度内研究区沉积物质是相对较为稳定的。

Environmental radiation of Holocene loess soil sequence in the middle part of the Henan province

In this paper,75 samples were collected from Holocene loess soil sequence in the middle part of the Hennan province and used to discover the environmental radiation of Holocene loess soil sequence.The concentrations of the uranium,thorium and potassium were determined by X-ray fluorescence.The natural dose-rate can be calculated through method of OSL dating that was given by Aitken in 1998 and used as proxy of environmental radiation.The results indicated that natural dose rate ranges from 7.87 to 24.67 mGy/a,with the mean of 19.86 mGy/a.The dose rates that appear in S0,Lt,L1 are higher and 20.58、23.19、22.47 mGy/a respectively.The analytical results indicated that dose-rate is influenced by the chemical composition of dust deposits and climate(especially the leaching of soluble elements).The variation of chemical composition of accumulated dust only has weak effect on the dose rate and leaching of soluble elements has a primary or major effect on dose rate or environmental radiation.In Holocene loess-soil sequences,the transformation of chemical composition of accumulated dust is of feebleness.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.