黄土洼后小滩沟沉积物理化特征及其揭示的环境信息

The Physical and Chemical Characteristics of Sediments in Houxiaotan Gully of Huangtuwa and Their Environmental Information

利用荧光光谱仪、激光粒度仪等仪器对黄土洼后小滩沟台地取得的950个沉积物样品进行测定,获取了淤地坝元素含量、粒度参数等多项指标。对粒度参数、元素含量进行分析研究,并揭示了相应的地球化学特征及环境信息。结果表明:黄土洼后小滩沟沉积物具有"二元结构"沉积旋回,进一步佐证了该地区次生黄土的水成说,且其中"细淤泥层"可以作为洪水沉积结束的重要标志;后小滩沟E剖面同主沟内C剖面的粒度分布差异表明了黄土洼地区泥沙运移主要受搬运距离的影响;在黄土洼后小滩沟聚湫沉积剖面中,常量元素中Si的含量最大,而Al、Ca等元素的含量相对次之;根据剖面元素同粒度参数的变化特征,可分为3类:Ⅰ类元素遵循"元素的粒度控制规律",元素同粒度参数有较好的相关性;Ⅱ类元素同部分粒度参数相关性较好;Ⅲ类元素不受粒度控制,而受元素自身性质、搬运营力等多重影响。并且进一步验证了黄土洼后小滩沟台地"先期沉积,后期侵蚀"的环境演变过程。研究结果为了解陕北黄土高原小流域土壤侵蚀、沉积物理化特征及其揭示的环境信息提供科学依据。

We measured the 950 sediment samples taken from Houxiaotan gully section of Huangtuwa by using fluorescence spectrometer and laser particle size analyzer,to investigate element contents,grain size parameters and many other indicators of silt dam in the purpose of revealing the corresponding geochemistry and environmental information.The results showed that the deposits of Houxiaotan gully had sedimentary cycle with the＂dual deposition＂structure,which further illustrated that the region＇s secondary loess was caused by flood deposition,and the＂fine-grained silt layer＂could be used as an important symbol of the end of flood deposition.The profile E of Houxiaotan gully greatly differed in particle size distribution with the profile C of the main gully,which showed that the sediment movement in Huangtuwa area was mainly affected by transport distance.Si showed the highest content among all major elements in the profile of dammed silt land,followed by Al and Ca.According to the variation characteristics of grain size parameters and element contents,the profile elements could be divided into 3categories：Class I elements followed the rule of＂granular control of elements＂,and there was a good correlation between element contents and grain size parameters.Class II elements had a good correlation with partial grain size parameters.Class III elements were not controlled by grain size parameters,but they were affected by the characteristics of themselves and transport force,which further documented the environment evolution process of＂deposition at early stage,erosion at later stage＂in Houxiaotan gully section of Huangtuwa.This study can provide a scientific basis for the soil erosion,physical and chemical characteristics of sediments and their environmental information on the Loess Plateau.