【作者】 桂洪杰；

【导师】 管清玉；

【作者基本信息】 兰州大学 ， 环境工程， 2013， 硕士

【摘要】 黄河宁蒙河段的腾格里沙漠、河东沙地、乌兰布和沙漠和库布齐沙漠是我国最重要的风沙活动区,其风沙活动不仅对我国沙尘天气有直接的推动作用,而且由于风沙活动导致风沙入黄,其中粒径大于0.1mm的沙粒在黄河中难以形成悬浮物质,多沉积于河道造成河道淤积。因此,对于黄河宁蒙河段四大沙漠的研究,长期以来受到国内外学者的广泛关注,但这些研究工作主要集中在单个沙漠,而对于沙漠间粒度特征的对比研究所进行的工作较少。本文就是在前人研究的基础上选取黄河宁蒙河段四大沙漠为研究对象,对其粒度和元素特征进行对比研究。通过对四大沙漠间地表沉积物的机械组成、众数、粒度参数及分形维数特征的研究,我们发现黄河宁蒙段四大沙漠地表沉积物从上游到下游粗颗粒组分(>0.1mm)含量呈现增大趋势,细颗粒组分(<0.1mm)呈现减小趋势；粒度参数特征表现为从上游到下游平均粒径、众数逐渐增大,分选性逐渐变好,粒度频率分布曲线分布属于中等峰态或窄峰态的正偏；地表沉积物的分形维数与沉积物的样品质地关系明确,即样品中粗颗粒组分含量越高或细颗粒组分含量越低,其分形维数值越小,反之亦然。通过对四大沙漠元素丰度、风化指标(Na/K、CIA、CPA)、富集因子(EF)、示踪元素与特征元素比值的研究,我们发现,黄河宁蒙河段四大沙漠常量元素氧化物、微量元素含量变化趋势具有很好相似性且变异系数都较低；常量元素氧化物中,除CaO在腾格里沙漠和河东沙地表现为相对富集,在另外两个沙漠表现为相对亏损,其余氧化物均表现为富Si02贫Fe2O3、Al2O3、MgO、Na2O和K20的特点；四大沙漠与洛川黄土和陆源页岩相比,均表现出富SiO2、CaO、Na2O贫Fe2O3、Al2O3、MgO、K2O的特征；微量元素中Ce元素表现为相对富集,Ba、Mn、Nb、Rb、Sr、Ti和V均表现为相对亏损；La元素除在腾格里沙漠相对富集外,其他三大沙漠均相对亏损,Nd元素则在腾格里沙漠和河东沙地相对富集,而在其他两个沙漠相对亏损。四大沙漠的风化趋势基本一致,即斜长石最先风化分解,Ca、Na流失,而钾长石较为稳定,其风化程度表现为腾格里沙漠>乌兰布和沙漠>河东沙地>库布齐沙漠；与洛川黄土、陆源页岩相比较,黄河宁蒙河段四大沙漠基本处于弱风化状态；沉积物Na／K比值与CPA变化有明显的负相关关系,而与CIA关系不明显。四大沙漠具有相同的地表沉积物来源,但其沉积环境、沉积过程和搬运动力存在差异。其中乌兰布和沙漠与库布齐沙漠最为相似,而与腾格里沙漠差异较大,河东沙地为腾格里沙漠与乌兰布和沙漠和库布齐沙漠的过渡区域。更多还原

【Abstract】 The Tengger Desert, Hedong sandy land, Ulan Buh Desert and Kubuqi Desert are the most important sand drifting areas in China, where the sand drifting activities not only directly improve the dusty wind weather, but also bring sand into the Yellow River. Sand with grain size>0.1mm can hardly form suspended solids, but mostly deposit in the watercourse to form the sedimentations of the waterways. Therefore, researches on the four deserts in Ningxia-Inner Mongolia section of the Yellow River have long attracted the attentions of scholars in China and foreign countries. There are extensive researches on the four deserts in Ningxia-Inner Mongolia section of the Yellow River, however, they are concentrated in the single desert, few comparative works on the characteristics of these four deserts were conducted. Based on the former researches, by studying the four deserts in Ningxia-Inner Mongolia section of the Yellow River, comparative researches on the features of grain sizes and elements were conducted in this paper.By studying mechanical composition, mode, grain size parameters and fractal dimension of the surface sediments in the four deserts, we found that the mechanical compositions of these samples were mainly fine sand and silt. From upstream to downstream, there is an increasing tendency in the contents of coarse particles(>0.1mm) of the four deserts, but a decreasing tend in fine particles(<0.1mm). Among the grain size parameters, mean grain size and mode are gradually increasing, sorting becomes better and granularity distribution frequency curves show a positive skewness and middle or narrow kurtosis. There is a very clear relationship between fractal dimension and sample texture of surface sediments in the four deserts, that is, the more the coarse particle content or the less the fine particle content, the smaller the fractal dimension values, and vice versa.By studying the element abundances, weathering indices(Na/K、CIA、CPA), enrichment factor(EF), tracer element and the ratio of the feature element, We found that the variation tendency of the common element oxides and the trace elements is similar, and both of their variable coefficients are relatively small. Among the common element oxides, CaO is relatively enriched in the Tengger Desert and the Hedong sandy land, but relatively less in the other two deserts. The rest of the oxides are characterized by being rich in SiO2, but less in Fe2O3, Al2O3, MgO, Na2O and K2O. Besides, compared with Luochuan Loess and terrigenous shale, the four deserts are all characterized by being rich in SiO2, CaO and Na2O, but less in Fe2O3, Al2O3, MgO and K2O. In these four deserts, the trace element Ce is relatively rich, but Ba, Mn. Nb, Rb, Sr, Ti and V are relatively less; La is enriched in the Tengger Desert, but less in the other three deserts. Nd is relatively enriched in the Tengger Desert and the Hedong sandy land, but less in the other two deserts.In these four deserts, the weathering trends are similar, namely plagioclase is firstly weathered and decomposed, with Ca and Na are quickly losing. Potash feldspar is better stable, its weathering degrees in these four deserts are:the Tengger Desert> the Ulan Buh Desert> the Hedong sandy land> the Kubuqi Desert. Compared with Luochuan Loess and terrigenous shale, the four deserts in Ningxia-Inner Mongolia section of the Yellow River are basically slightly weathered. There is obvious negative correlation between the values of Na/K in the sediment and CPA, but unobvious relationship between the values of Na/K in the sediment and CIA.There are similar surface sediment sources, but differernt sedimentary environment, deposition processes and handling process in the four deserts. The Ulan Buh Desert is similar with the Kubuqi Desert, but different from the Tengger Desert, the Hedong sandy land in the transition region of the Tengger Desert and the Ulan Buh Desert.更多还原