Geochemical characteristics of Holocene aeolian deposits and their environmental significance in the Mu Us Desert,northern China     

Bing Liu  He‐Ling Jin  Liang‐Ying Sun  Zhong Sun  Qing‐He Niu  Cai‐Xia Zhang 《Geological Journal》2016,51(3):325-337

This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand–palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO₂, Al₂O₃, and Na₂O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm–wet and cold–dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial‐scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial‐scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

利用原子荧光光谱-电感耦合等离子体质谱法研究济南市大气干湿沉降重金属含量及年沉降通量特征   总被引：2，自引：1，他引：1  

赵西强  庞绪贵  王增辉  战金成 《岩矿测试》2015,34(2):245-251

大气降尘是地表土壤重金属元素的重要来源,研究大气降尘中重金属元素的地球化学特征并进行源解析对制定污染防控政策具有重要的指导作用。本文采用原子荧光光谱法、电感耦合等离子体质谱法、X射线荧光光谱法分析济南市大气干湿沉降中8种重金属(砷镉铬铜汞镍铅锌)含量特征;采用相关分析及主成分分析方法对大气干湿沉降重金属进行源解析。结果表明,大气干湿沉降物中镉铬铜汞镍铅锌平均含量分别为2.07 mg/kg、135.9 mg/kg、65.7 mg/kg、218.6μg/kg、110.7 mg/kg、380 mg/kg,显著高于土壤背景值,且富集程度高,明显受人为活动污染。镉铜汞铅主要来源于燃煤,砷铬来源于道路尘,镍来源于土壤,锌来源于交通尘;燃煤和道路尘对大气降尘的贡献率为50.13%,两者是济南市大气降尘污染的主要来源。大气干湿沉降对城区表层土壤中镉汞铬铅锌及砷的含量水平影响显著,其中锌年沉降通量最高(均值148 mg·m-2·a-1),汞年沉降通量最低(均值0.085 mg·m-2·a-1),且镉汞含量增长速率较高;大气干湿沉降对砷铬在土壤中的累积影响显著。  相似文献   

基于选权迭代法的GPS/北斗组合单点定位     

何俊  袁小玲  刘万科 《测绘信息与工程》2014,(4):21-23

介绍了GPS/北斗组合单点定位的数学模型,采用IGG-Ⅲ方案对单/双系统单点定位进行定权,并将结果与等权处理结果作比较。分析表明,对于单系统而言,GPS/北斗组合可以显著增加可用卫星数,降低pDop值,提高定位精度;无论是单系统还是组合系统,使用选权迭代法均能在一定程度上改善定位精度,提高解算成功率,且对组合定位效果更佳。  相似文献   

Preparation of polysaccharides in different molecular weights from Ulva pertusa Kjellm (Chorophyta)     

Yu Pengzhan  Zhang Quanbin  Zhang Hong  Niu Xizhen  Li Zhien 《中国海洋湖沼学报》2004,22(4):381-385

As molecular weight controls the biological activities of polysaccharides, screening the optimal molecular weight of polysaccharides is important in drug research and application. In this study, hydrogen peroxide was employed as oxidant, and temperature, reaction time, and concentration of polysaccharides and hydrogen peroxide were examined for their effects on the preparation of polysaccharides in different molecular weights fromUlva pertusa. Our experiment suggested that the optimal degradation concentrations for polysaccharides and hydrogen peroxide were 2.5% (w/v) and 8.0% (v/v), respectively. The range of degradation measured by relative viscosity was mainly controlled by temperature and time. Results revealed that 35°C was the optimal temperature for obtaining low-degradation samples, and 50°C was the most favorable temperature to accelerate the reaction to yield highly-degraded samples. Four samples in different molecular weights A, B, C and D were finally prepared. The controllability was evaluated by the relative standard deviation (RSD) of relative viscosity, and the peak molecular weights and the polydispersity indexes (M_w/M_n) of molecular weights were measured by high performance gel permeation chromatography (HPGPC). This work was supported by the Scientific and Technical Bureau of Shandong Province.  相似文献   

基于流形学习的航空影像匹配方法研究     

付冬暇  赵淮  李爱霞 《测绘与空间地理信息》2013,(8):138-140

提出了一种基于流形学习的航空影像匹配方法。该方法利用同一幅影像中特征点之间的空间结构和不同影像中特征点之间的相似性作为特征点映射的约束条件,利用流形学习方法对影像的特征点进行映射,将所有影像的特征点映射到同一空间后采用最小距离方法进行特征点的匹配。利用实际的航空影像进行实验,与SIFT方法、SVD-LLE方法进行综合分析,结果表明本文方法在匹配性能方面具有明显的优越性,并且能够同时获得多幅影像之间的匹配关系。  相似文献   

Mass‐balance modeling of mineral weathering rates and CO2 consumption in the forested,metabasaltic Hauver Branch watershed,Catoctin Mountain,Maryland, USA     

Jason R. Price  Karen C. Rice  David W. Szymanski 《地球表面变化过程与地形》2013,38(8):859-875

Mineral weathering rates and a forest macronutrient uptake stoichiometry were determined for the forested, metabasaltic Hauver Branch watershed in north‐central Maryland, USA. Previous studies of Hauver Branch have had an insufficient number of analytes to permit determination of rates of all the minerals involved in chemical weathering, including biomass. More equations in the mass‐balance matrix were added using existing mineralogic information. The stoichiometry of a deciduous biomass term was determined using multi‐year weekly to biweekly stream‐water chemistry for a nearby watershed, which drains relatively unreactive quartzite bedrock. At Hauver Branch, calcite hosts ~38 mol% of the calcium ion (Ca²⁺) contained in weathering minerals, but its weathering provides ~90% of the stream water Ca²⁺. This occurs in a landscape with a regolith residence time of more than several Ka (kiloannum). Previous studies indicate that such old regolith does not typically contain dissolving calcite that affects stream Ca²⁺/Na⁺ ratios. The relatively high calcite dissolution rate likely reflects dissolution of calcite in fractures of the deep critical zone. Of the carbon dioxide (CO₂) consumed by mineral weathering, calcite is responsible for approximately 27%, with the silicate weathering consumption rate far exceeding that of the global average. The chemical weathering of mafic terrains in decaying orogens thus may be capable of influencing global geochemical cycles, and therefore, climate, on geological timescales. Based on carbon‐balance calculations, atmospheric‐derived sulfuric acid is responsible for approximately 22% of the mineral weathering occurring in the watershed. Our results suggest that rising air temperatures, driven by global warming and resulting in higher precipitation, will cause the rate of chemical weathering in the Hauver Branch watershed to increase until a threshold temperature is reached. Beyond the threshold temperature, increased recharge would produce a shallower groundwater table and reduced chemical weathering rates. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

基于GIS的汶川县地质环境安全综合评价     

汪留洋  ;秦美玉那 《中国煤炭地质》2014,(11):39-45

汶川县内地质构造复杂,新构造运动强烈,地震活动频繁,主要地质环境问题以地质灾害为主,有崩塌、滑坡、泥石流等。在分析区内主要地质环境问题及分布特征的基础上,运用层次分析法（AHP）确定权重,采用模糊综合评判模型、综合指数模型两种方法,对汶川县地质环境安全进行综合评价。详细介绍基于GIS的评价计算流程及评价因子的提取过程。评价结果表明,地质环境对居民生产生活影响的危险等级占比为：危险性低的约占25%,危险性较低的约占20%,危险性较高的约占39%,危险性高的约占16%。对两组权重系数、两个模型下的四个评价结果进行对比分析,结果发现：1两组不同权重系数下,模糊评价法和综合指数法评价结果的双侧检验相关系数依次是0.97、0.98,属于高度显著相关,表示可以忽略人为赋权重对评价结果的主观影响;2两种不同模型下,评价结果的双侧检验相关系数依次是0.895、0.84、0.92、0.914,属于显著相关,表示不同的计算模型一定程度上影响了评价结果的准确性,在评价时要认真研究选择恰当的计算模型。  相似文献   

层次分析法在地下水质量评价中的应用   总被引：1，自引：0，他引：1  

高宗军  董红志  许传杰  付青  王世臣 《地下水》2014,(3):49-50

开展区域地下水质量评价,突出主导因子对地下水质量的影响,提出将层次分析法引入地下水评价中,以单因子评价结果为基础对地下水质量进行二次评价。构建层次结构模型并组建专家组进行讨论,最终以专家打分的方式确定评价中各个因子的权重。分别对Q1, Q2两组地下水质数据进行单因子评价、内梅罗指数综合评价以及层次分析评价。对比评价结果发现,层次分析法能够在突出主导因子对水质评价的贡献的基础上,更为真实地反映区域地下水质量状况。  相似文献   

某电厂水库岸边取水工程施工实践          下载免费PDF全文

李建斌  刘国谋  赵存宝  李丽  袁慧敏 《探矿工程》2014,41(2):74-77,81

为满足某电厂供水需求,需在某水库进行岸边取水工程（含取水竖井、引水隧道、引水明渠3部分）施工。通过短段掘砌逆作工艺,井筒壁溶洞导水并将导出的水作为水源的一部分,实现了井筒干封底,顺利完成井筒施工;采用顶管技术＋管顶注浆技术在破碎岩体、涌水量较大地层成功完成引水隧道施工;通过岩塞爆破成功实现引水隧道和水库的连接;通过船载冲击成槽技术,实现了引水明渠的施工。  相似文献   

分散性土的抗剪强度特性试验研究   总被引：2，自引：0，他引：2  

唐自强  党进谦  樊恒辉 《岩土力学》2014,299(2):435-440

分散性土是一种具有特殊工程性质的土,其典型的性质为抗渗性能差,耐冲蚀能力低,在纯水中具有很高的分散性。目前,人们对于分散性土的研究主要集中在鉴定、抗渗和改良等方面,而对其抗剪强度特性的研究很少。采用三轴CU试验研究不同初始条件下分散性土的抗剪强度特性。结果表明:分散性土的应力-应变曲线在小围压、低含水率和高干密度的状态下呈应变软化型,在围压较大、含水率较高的情况下呈弱硬化型或硬化型;黏聚力和内摩擦角均随含水率的增大而减小,并且干密度越大受水分影响越强烈;黏聚力随干密度的增大而增大,在低含水条件下,黏聚力的增幅较大,而在高含水条件下,黏聚力的增幅则较小;内摩擦角随干密度的增大有少量增大。  相似文献