Suspended sediment and total dissolved solid yield patterns at the headwaters of Urumqi River,northwestern China: a comparison between glacial and non‐glacial catchments          下载免费PDF全文

Wenhua Gao  Shu Gao  Zhongqin Li  X. X. Lu  Mingjun Zhang  Shengjie Wang 《水文研究》2014,28(19):5034-5047

In order to understand the differences in the suspended sediment and total dissolved solid (TDS) yield patterns between the glacial and non‐glacial catchments at the headwaters of Urumqi River, northwestern China, water samples were collected from a glacier catchment and an empty cirque catchment within the region, during three melting seasons from 2006 to 2008. These samples were analyzed to estimate suspended sediment and TDS concentrations, fluxes and erosion rates in the two adjoining catchments. There were remarked differences in suspended sediment and TDS yield patterns between the two catchments. Suspended sediment concentrations were controlled mainly by the sediment source, whereas TDS concentrations were primarily related to the hydrologic interaction with soil minerals. Generally, the glacial catchment had much higher suspended sediment and TDS yields, together with higher denudation rates, than the non‐glacial catchment. Overall, glacial catchment was mainly dominated by physical denudation process, whereas the non‐glacial catchment was jointly influenced by physical and chemical denudation processes. The observed differences in material delivery patterns were mainly controlled by the runoff source and the glacial processes. The melting periods of glacier and snow were typically the most important time for the suspended sediment and TDS yields. Meanwhile, episodic precipitation events could generate disproportionately large yields. Subglacial hydrology dynamics, glaciers pluck and grind processes could affect erodibility, and the large quantities of dust stored on the glacier surface provided additional sources for suspended sediment transport in the glacial catchment. These mechanisms imply that, in response to climate change, the catchment behaviour will be modified significantly in this region, in terms of material flux. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Pre‐ and post‐impoundment nitrogen in the lower Missouri River          下载免费PDF全文

Dale W. Blevins  Donald H. Wilkison  Shelley L. Niesen 《水文研究》2014,28(4):2535-2549

Large water‐sample sets collected from 1899 through 1902, 1907, and in the early 1950s allow comparisons of pre‐impoundment and post‐impoundment (1969 through 2008) nitrogen concentrations in the lower Missouri River. Although urban wastes were not large enough to detectably increase annual loads of total nitrogen at the beginning of the 20^th century, carcass waste, stock‐yard manure, and untreated human wastes measurably increased ammonia and organic‐nitrogen concentrations during low flows. Average total‐nitrogen concentrations in both periods were about 2.5 mg/l, but much of the particulate‐organic nitrogen, which was the dominant form of nitrogen around 1900, has been replaced by nitrate. This change in speciation was caused by the nearly 80% decrease in suspended‐sediment concentrations that occurred after impoundment, modern agriculture, drainage of riparian wetlands, and sewage treatment. Nevertheless, bioavailable nitrogen has not been low enough to limit primary production in the Missouri River since the beginning of the 20^th century. Nitrate concentrations have increased more rapidly from 2000 through 2008 (5 to 12% per year), thus increasing bioavailable nitrogen delivered to the Mississippi River and affecting Gulf Coast hypoxia. The increase in nitrate concentrations with distance downstream is much greater during the post‐impoundment period. If strategies to decrease total‐nitrogen loads focus on particulate N, substantial decreases will be difficult because particulate nitrogen is now only 23% of total nitrogen in the Missouri River. A strategy aimed at decreasing particulates also could further exacerbate land loss along the Gulf of Mexico, which has been sediment starved since Missouri River impoundment. In contrast, strategies or benchmarks aimed at decreasing nitrate loads could substantially decrease nitrogen loadings because nitrates now constitute over half of the Missouri's nitrogen input to the Mississippi. Ongoing restoration and creation of wetlands along the Missouri River could be part of such a nitrate‐reduction strategy. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

Cathodoluminescence and Trace Element Composition of Scheelite from the Middle-Lower Yangtze River Metallogenic Belt (MLYB): Implications for Mineralization and Exploration     

NIE Liqing  ZHOU Taof  CHEN Xuefeng  WANG Fangyue  XIAO Xin 《《地质学报》英文版》2020,94(6):1977-1996

The Middle–Lower Yangtze River Metallogenic Belt (MLYB) is known to contain abundant copper and iron porphyry-skarn deposits, with an increasing number of tungsten deposits and scheelite in Fe–Cu deposits being discovered in the MLYB during recent decades. The ore genesis of the newly-discovered tungsten mineralization in the MLYB is poorly understood. We investigate four sets of scheelite samples from tungsten, iron and copper deposits, using CL imaging and LA–ICP–MS techniques to reveal internal zonation patterns and trace element compositions. The REE distribution patterns of four studied deposits show varying degrees of LREE enrichment with negative Eu anomalies. The oxygen fugacity of ore-forming fluid increased in Donggushan, while the oxygen fugacity of ore-forming fluid decreased in Ruanjiawan, Guilinzheng and Gaojiabang. The scheelites from the Donggushan, Ruanjiawan, Guilinzheng and Gaojiabang deposits show enrichment in LREEs and HFSE, with Nb/La ratios ranging from 1.217 to 52.455, indicating that the four tungsten deposits are enriched in the volatile fluorine. A plot of (La/Lu)N versus Mo/δEu can be used to distinguish quartz vein type, porphyry and skarn tungsten deposits. This study demonstrates that scheelite grains can be used to infer tungsten mineralization and are effective in identifying magmatic types of tungsten deposits in prospective mining sites.  相似文献   

巢湖杭埠河流域湖相沉积物多指标揭示的全新世以来环境演变     

周慧  吴立  马春梅  管后春  孙小玲  路曙光  尚广春  汪勇  徐仪红  徐军  陈晔  鲍远航 《湖泊科学》2020,32(6):1869-1881

在巢湖杭埠河流域中的古湖盆中心——三河圩区获取28.6 m长的湖相岩芯（SZK1507孔），利用AMS¹⁴C测年技术建立可靠的地层年代序列，通过对SZK1507孔738 cm以上段湖相沉积物平均粒径、磁化率、总氮（TN）、总有机碳（TOC）及C/N的综合分析，高分辨率重建了巢湖杭埠河流域全新世以来的古环境演变过程.结果表明，本区域的环境变化过程可以分为4个阶段，阶段Ⅰ（约10050—9700 cal.a B.P.）与阶段Ⅲ（约9250—5300 cal.a B.P.）气候较为湿润，巢湖水位较高，平均粒径、磁化率值较低，TN、TOC、C/N也偏低；阶段Ⅱ（约9700—9250 cal.a B.P.）与阶段Ⅳ（约5300 cal.a B.P.以来）气候干燥，巢湖水量减少，水位降低，平均粒径、磁化率值、TN、TOC、C/N均较高.一些全球范围内显著发生的气候突变事件在SZK1507孔沉积记录中也有体现，如9.3、8.2和4.2 ka B.P.事件等.将巢湖杭埠河流域10000 cal.a B.P.以来的平均粒径、磁化率、TN、TOC、C/N沉积记录与全新世以来的北纬30°夏季太阳辐射量、太阳黑子数、火山喷发对大气中硫酸盐含量贡献率等进行对比，发现巢湖杭埠河流域全新世气候突变事件主要受控于北半球夏季太阳辐射量变化、太阳活动以及火山活动等因素，并与它们之间复杂的响应机制有关.  相似文献   

珠江口盆地荔湾凹陷上渐新统—早中新统物源特征及其对沉积充填的影响     

邢作昌  张忠涛  林畅松  张博  洪方浩  张正涛 《中国地质》2020,47(5):1577-1588

利用化学蚀变指数法恢复物源区的风化历史及沉积物通量是一种经济实用、行之有效的方法。前人对珠江口盆地荔湾凹陷对应物源区的研究相对薄弱。本文通过对区内岩心测试数据进行化学蚀变指数分析，恢复晚渐新世—早中新世物源区的风化历史，并进行沉积物通量的估算，在此基础上探讨物源特征对研究区内沉积充填的控制作用。研究表明，晚渐新世研究区对应物源区经历了强烈风化阶段，该阶段产生的丰富的沉积物供给是研究区西北部快速进积、规模壮观的陆架边缘三角洲及斜坡重力流沉积体系发育的重要控制因素之一；早中新世，西北物源区风化减弱，沉积供给减少，但研究区东部沉积物供应较西部要充分得多，表明早中新世，研究区南部除了来自西北部的主要物源外，局部物源对该时期的沉积具有重要影响；推测东部物源(东部古隆起、兴宁古隆起)的突然复活是促进研究区东部早中新世沟槽形成发育的重要原因之一。在超深水区进行沉积物源区的研究中，这种半定量的方法对盆内局部物源的确定具有重要的指示意义。  相似文献   

Terraces Development and Their Implications for Valley Evolution of the Jinsha River Since Late Pleistocene near Longjie,Yunnan     

Fenliang Liu  Hongshan Gao  Zongmeng Li  Baotian Pan  Huai Su 《地球科学进展》2020,35(4):431-440

The drainage evolution and valley development of the Jinsha River is an important issue constantly concerned by researchers in geology and geomorphology. Despite hundreds of years of research, there is a big dispute on the formation time and the evolution process of the fluvial valley. Fluvial terraces are very important geomorphic markers for studying the formation and evolution of the fluvial valley. Through field investigation combined with Electron Spin Resonance (ESR) dating, we confirmed that 5 fluvial terraces were formed, and then preserved, along the course of the Jinsha River near the Longjie, which are all strath terraces. Among them, T5 developed on the base rock, with an age of (78±12) ka; all T4~T1 developed on the lacustrine sediments, named Longjie Group by Chinese, with an age of (29±1.4) ka, (26±2.4) ka, (23±1.4) ka, (18±1.7) ka, respectively. Compared with the global and regional climate change history, the terraces are all the result of the river responding to the climate change. T5 formed at MIS 5/4, and T4~T1 formed at the period of regional climate fluctuation. The relationship of terraces and the Longjie Formation, combined with sedimentary characteristics analysis demonstrate that the Longjie Formation is landslide dammed lake sediment. The landslide and blocking events.seriously influenced the valley evolution, inhibiting the river incising, and making the valley evolution defer to the mode of “cut-landside-damming-fill-cut” in the period of Late Pleistocene. Synthesized studies of the terraces and the correlative sediments indicate that the formation of the Jinsha River valley may have begun in the late Early Pleistocene.  相似文献   

天山南坡高冰川覆盖率的木扎提河流域水文过程对气候变化的响应   总被引：5，自引：5，他引：0  

赵求东  赵传成  秦艳  苌亚平  王建 《冰川冻土》2020,42(4):1285-1298

木扎提河是天山南坡冰川面积覆盖率最大（48.2%）的河流， 流域径流过程对气候变化极为敏感， 为了合理管理和规划水资源， 确保水资源的可持续利用， 亟需定量评估气候变化对该流域水文过程的影响。以VIC-CAS分布式水文模型为计算平台， 利用实测的径流和两次冰川编目间的冰川面积变化数据开展了模型的多目标参数化校正和验证， 有效提高了模拟结果的“真实性”， 然后通过数值模拟结果结合观测数据定量解析了流域径流的组成、 变化特征及对气候变化的响应机理。结果表明： 木扎提河总径流集中在暖季（5 - 9月）， 占全年总径流量的77.9%， 冰川径流、 融雪径流和降雨径流分别占总径流量的66.6%、 26.4%和7.0%。1971 - 2010年木扎提河流域气温和降水呈显著增加趋势， 由于降水的增加， 降雨和融雪径流均呈增加趋势， 但冰川径流呈现明显减少趋势， 导致总径流呈现下降趋势。在RCP4.5情景下， 未来该流域气温呈现明显升高趋势， 降水表现为微弱下降趋势； 气候变暖后， 更多降水以降雨形式发生， 未来降雨径流将明显增加， 降雪和融雪径流已于20世纪90年代达到峰值， 随后明显减少； 冰川面积将持续萎缩， 冰川径流于21世纪10年代达到拐点， 随后明显减少， 导致河道总径流量也将明显减少。  相似文献   

文昌B凹陷差异伸展- 走滑机制及控藏作用研究     

江汝锋  周家雄  杨希冰  游君君  李珊珊  陈林  张霞 《地质学报》2020,94(8):2422-2432

为查明文昌B凹陷油气富集差异性的原因，基于断裂展布和形成期次、构造样式组合、构造演化和断层活动的差异等标志，建立了差异伸展- 走滑机制，识别出19洼为伸展- 强走滑、14洼为伸展- 中等走滑、30洼为伸展- 弱走滑。差异伸展- 走滑作用控制了优质烃源岩的展布和供烃方向，控制输导体系类型和运移动力，提供物源通道和改造储层，还控制了圈闭类型和力学性质。进一步深化了走滑增压理论，基于先存断裂形态、伸展应力场右旋演化和应变差异，建立了走滑增压圈闭识别方法，识别出S型增压、右行左阶增压、斜交型增压3种走滑增压构造。研究表明，文昌B凹陷的油气富集受伸展- 走滑构造背景、源- 运时空配置关系所控制，强—中等走滑变形、发育优质中深湖源岩的文昌19洼和14洼是油气富集区。该研究成果成功推动了文昌凹陷近期的多个勘探发现。  相似文献   

石羊河下游人工梭梭林土壤呼吸变化特征及其与水热因子的关系          下载免费PDF全文

王新友  马全林  靳虎甲  樊宝丽  张进虎  林慧龙 《干旱区地理》2019,42(3):570-580

土壤呼吸不仅是反映土壤生物活性的重要指标，也是全球碳循环研究中备受关注的热点问题。在地处典型干旱区的石羊河下游，以流动沙丘和去除土壤结皮人工梭梭林为对照，采用LI-8100土壤碳通量监测系统研究了栽植约40 a、30 a、10 a和5 a的人工梭梭林生长季和非生长季的土壤呼吸日变化，并分析了土壤水分和温度对土壤呼吸的影响。结果表明：（1）不同林龄梭梭林生长季和非生长季土壤呼吸速率的日变化均为明显的单峰曲线，且呈现出一定的波动性，日最大排放速率出现在12:00～14:00时，最小值出现在8:00时左右。（2）梭梭林营造和去结皮处理显著提高了沙漠土壤呼吸速率，而且不同林龄土壤呼吸速率大体上随着种植年限的增加而递增，表现为MC >40 a>30 a>10 a>MS >5 a，非生长季表现为MC >40 a>10 a>5 a>30 a>MS。（3）不同林龄梭梭林土壤呼吸速率均具有明显的季节变化特征，生长季（8 月）的土壤呼吸作用明显强于非生长季（1月）。（4）相关性分析表明，生长季和非生长季土壤呼吸均与0～5 cm土壤水分显著相关，且均呈二次曲线关系，分别为Y =-0.205 8X ²+0.946 5X-0.316 6（R ² =0.506 ²，P= 0.041 7）和Y= 0.118 7 X ²+0.156 3X+0.118 8（R ²=0.675 7，P =0.001 1）；但与10 cm土壤温度的相关性不显著，土壤水分是影响人工梭梭林土壤呼吸的关键因素。该研究进一步证明了人工梭梭林的营造有效改善了沙漠土壤的生物活性，提高了土壤碳通量水平，以土壤结皮破坏为基本特征的人工梭梭林退化和沙漠化必然在短期内加剧碳排放。因此，需要在沙漠地区合理营造人工林，并在造林和林业管理过程中注意保护土壤结皮，以减少CO²排放。  相似文献   

Developing a comprehensive evaluation method for Interconnected River System Network assessment: A case study in Tangxun Lake group     

Yang  Wei  Zhang  Liping  Zhang  Yanjun  Li  Zongli  Xiao  Yi  Xia  Jun 《地理学报(英文版)》2019,29(3):389-405

Journal of Geographical Sciences - The Interconnected River System Network (IRSN) plays a crucial role in water resource allocation, water ecological restoration and water quality improvement. It...  相似文献