Physicochemistry and Mineralogy of Storm Dust and Dust Sediment in Northern China   总被引：2，自引：0，他引：2  

LIU Wei  FENG Qi  WANG Tao  ZHANG Yanwu  SHI Jianhua 《大气科学进展》2004,21(5):775-783

Dust sediments collected from 1995 to 1998 in Beijing, Dunhuang, Inner Mongolia, Kashi, the Kunlun Mountains, Lanzhou, Ningxia, the Taklimakan Desert, and Xi‘an, China, were characterized in terms of their physical, chemical, and mineralogical properties. Most aerosols and dust analysed ranged in texture from silty clay to clay loam. Their median particle diameters (Mds) generally ranged between 5 to 63μm,coinciding with those of loess from central China and the finest sand from northwestern China. The dust sediments were characterized by a predominance of SiO2 and Al2O3, followed by K2O. Their SiO2/Al2O3and K2O/SiO2 molar ratios ranged from 5.17 to 8.43 and from 0.009 to 0.0368, respectively. The mass concentration spectrum during a dust storm showed a single peak, rather than the triple peak generally observed under clear sky conditions. The dominant minerals were chlorite, illite, calcite, and dolomite.These physical, chemical, and mineralogical properties were consistent with those of aeolian soils and loess in western and central China. The results suggest that aerosols and fine-gained fractions of dust sediments collected in northern China are mainly composed of soil material transported from the arid and semiarid regions of China and Mongolia by prevailing winds. The rate of deposition and properties of dust falling on eastern China were strongly influenced by meteorological conditions, season, latitude, longitude, and altitude of the sampling sites.  相似文献   

影响C₄草本植物C/N比值变化的因素与土壤有机C积累的关系   总被引：6，自引：1，他引：6       下载免费PDF全文

朴河春  朱建明  余登利  冉景丞 《第四纪研究》2004,24(6):621-629

文章对采自贵州从低海拔的东部到高海拔的西部且大致平行的石灰岩和砂岩两地带均生长的3种C₄草本植物,即巴茅(Miscanthusfloridulus)、白茅(Imperatacylindrica)和类芦(Neyraudiareynaudiana),以及相对应的土壤表层样品,进行了营养元素和C同位素组成分析;研究营养元素含量随着海拔的不同而出现的变化趋势,以及这些元素之间的相互协变作用,尤其是Ca和N之间的相互协变作用对植物的N含量、C/N比值和^δ13C值的影响,以了解植物的C/N比值(指示植物残留物质量的一种标志)与土壤有机C积累的关系。研究结果表明,植物的N含量和^δ13C值具有随海拔的上升而显著增大趋势,而植物的C/N比值在砂岩地区虽有减小的趋势,在石灰岩地带则没有。对所研究的C4草本植物来说,在土壤pH值为5.8的中性条件下显示出Ca的最大吸收,因此,Ca与其他营养元素之间的协变模式在两种土壤类型中表现出相反的倾向,并存在土壤交换性Ca的边界浓度:当土壤可交换性Ca的含量为2.24mg/g,相应土壤的pH值在5.8以下时,随着土壤可交换性Ca浓度的增大,植物的N含量上升,而植物的C/N比值会显著降低;当Ca在边界浓度以上时,随着土壤可交换性Ca浓度的增大,植物的N含量下降,而植物的C/N比值有增加的趋势。由此可见,植物残留物的N含量和C/N比值受Ca元素含量的相  相似文献   

长江中游洪水沉积特征与标志初步研究   总被引：4，自引：0，他引：4       下载免费PDF全文

李长安  张玉芬 《水科学进展》2004,15(4):485-488

洪水记录是研究洪水规律的重要依据。通过对1998、1999、2002年长江中游洪水沉积物的系统观察、对比和研究,结果表明,长江中游洪泛沉积在沉积体形状、沉积结构和沉积物成分等方面,具有与正常河道沉积明显不同的特点,可为古洪水事件确定提供可能和依据。根据沉积环境的不同,长江中游洪泛沉积大致可分为3种类型:溃口洪水事件的沉积、滨岸带的洪水沉积和洪水漫滩沉积。进而对各种类型的沉积学特征进行了分析、归纳和总结,初步建立了其识别标志。  相似文献   

重金属迁移转化模型研究   总被引：14，自引：0，他引：14       下载免费PDF全文

何用  李义天 《水科学进展》2004,15(5):576-583

大量重金属污染物迁移转化的现象和研究成果都表明重金属以泥沙颗粒为载体迁移转化,描述重金属在天然水体中的迁移转化必须紧紧抓住泥沙颗粒运动及重金属与泥沙之间的转化关系进行.为此在对现有的重金属迁移转化数学模型进行概括分类的基础上,根据水沙运动与污染物相互作用关系,分析了泥沙颗粒运动及重金属吸附解吸不平衡过程,并结合水沙数学模型,建立了重金属迁移转化的耦合模型.同时在模型合理性分析的基础上,对模型进行了计算分析,分析表明模型能够合理地反映重金属污染物在水体中的迁移转化过程.  相似文献   

液压传感间接测量水位计的研制及其应用     

胡兴艺  丁跃进  王建家  汤文科  唐朋辉 《水文》2004,24(4):47-49

压力式水位计在水文自动测报系统中很难推广的主要原因是泥沙对传感器的影响,泥沙不但会使传感器测量精度达不到测验要求,而且由于泥沙淤积还会给水位计的日常维护带来很大不便。目前进口传感器测量精度高、稳定性能好,但仍避免不了泥沙的影响。针对这一问题,提出了一种新型压力式水位计———液压传感间接测量水位计,该水位计解决了泥沙对压力式水位计的影响,是一种具有很大发展前景的水位测量仪器。  相似文献   

栖霞组沉积地球化学特征及其环境意义   总被引：2，自引：1，他引：2  

施春华  胡瑞忠  颜佳新 《矿物岩石地球化学通报》2004,23(2):144-148

沉积环境的古氧相特征是沉积环境和古海洋特征恢复的重要内容。岩石地球化学特征是判断其形成环境氧化还原条件的重要手段之一。本文以来宾地区铁桥面为重点．通过对栖霞组灰岩的地球化学分析，结合沉积学、古生态学特征．认为栖霞组沉积于贫氧的沉{只背景．是在海水深度和海域的局限程度等沉积条件发生周期性变化的情况下形成的。古氧相地球化学指标V(V十Ni)、Cc/La、U／Th值都适用于该组以钙质沉积为主的沉积物。黄铁矿矿化程度(DOP值)变。化较大．眨映该区多变的古氧相特征。  相似文献   

碎屑流沿坡面运动的初步分析   总被引：1，自引：0，他引：1  

鲁晓兵  王义华  王淑云  崔鹏 《岩土力学》2004,25(Z2):598-600

本文分析了碎屑流沿坡面下滑过程中的运动特性,重点考察了床面摩擦系数、土体内摩擦角和坡角对碎屑流堆积形态的影响.  相似文献   

三峡大坝建成后长江输沙量的减少及其对长江三角洲的影响   总被引：3，自引：1，他引：3  

李从先  杨守业  范代读  赵娟 《第四纪研究》2004,24(4):495-500

三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×10⁸～2.5×10⁸t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×10⁸～2.28×10⁸t。二者的数值相当接近,然而与近50年的观测(4.33×10⁸t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。  相似文献   

Privatizing conditions of production: trade agreements as neoliberal environmental governance     

James McCarthy 《Geoforum》2004,35(3):327-341

Recent multilateral trade agreements are among the major manifestations of neoliberalism. They are also emerging as some of the most important sites of environmental governance in the 21st century. I argue here that these trade agreements, particularly the sweeping new protections they provide for investors, are redefining property rights and environmental governance in fundamental ways. I suggest that in addition to furthering the centuries-long process of the enclosure of nature under capitalism, the neoliberal agenda of NAFTA and similar trade agreements also involves something new: the privatization, or primitive accumulation, of conditions of production as an accumulation strategy. I explore these dynamics through examination of two cases, one in the United States and one in Mexico. I also explore the roles of social movements in these dynamics.  相似文献   

Inferring the mass fraction of floc-deposited mud: application to fine-grained turbidites   总被引：1，自引：0，他引：1  

K. J. Curran  P. S. Hill  T. M. Schell  T. G. Milligan†  D. J. W. Piper‡ 《Sedimentology》2004,51(5):927-944

Fine sediment deposition in the ocean is complicated by the cohesive nature of muds and their tendency to flocculate. The result is disaggregated inorganic grain size (DIGS) distributions of bottom sediment that are influenced by single‐grain and floc deposition. This study outlines a parametric model that characterizes bottom sediment DIGS distributions. Modelled parameters are then used to infer depositional conditions that account for the regional variation in the grain sizes deposited by turbidity currents on the Laurentian Fan–Sohm Abyssal Plain, offshore south‐eastern Canada. Results indicate that, on the channellized Laurentian Fan, the mass fraction of floc‐deposited mud increases only slightly downslope. The small evolution in this fraction arises because sediment concentration and turbulent energy are associated in turbidity currents. On the Sohm Abyssal Plain, however, the mass fraction of floc‐deposited mud decreases, probably as a result of lower sediment concentration at this source‐distal site. Estimates of the mass fraction of mud deposited as flocs suggest that floc deposition is the dominant mode by which sediment is lost from suspension, although single‐grain deposition contributes more to the depositional flux in proximal areas where high energy breaks flocs and in distal areas where low sediment concentration limits floc formation. It is concluded that, throughout the dispersal system, changes in the fraction of flocculated mud deposited from turbidity currents reflect changes in sediment concentration and energy downslope.  相似文献