Magnetic properties of tidal flat sediments of the Yangtze Estuary and its relationship with particle size   总被引：6，自引：0，他引：6  

张卫国  俞立中 《中国科学D辑(英文版)》2003,46(9):954-966

Since the 1970s, environmental magnetism has found extensive applications in diverse research areas of geoscience[1]. In China, a lot of environmental magnetic studies have been carried out on loess, lake and marine sediments for the purpose of paleoclima…  相似文献   

Morphological response of tidal marshes,flats and channels of the Outer Yangtze River mouth to a major storm   总被引：2，自引：0，他引：2  

Shi-Lun?YangEmail author  Carl?T.?Friedrichs  Zhong?Shi  Ping-Xing?Ding  Jun?Zhu  Qing-Ying?Zhao 《Estuaries and Coasts》2003,26(6):1416-1425

Systematic morphological changes of the coastline of the outer Yangtze River mouth in response to storms versus calm weather were documented by daily surveys of tidal marshes and flats between April 1999 and May 2001 and by boat surveys offshore during this and earlier periods. The largest single event during 1999 to 2001 was Typhoon Paibaian, which eroded the unvegetated tidal flat and lower marsh and led to accretion on the middle-to-upper marsh and in the subtidal channel. The greatest erosion of 21 cm occurred at the border between the marsh and the unvegetated flat due to the landward retreat of the marsh edge during the storm. Strong waves on the flats increased suspended sediment concentration by 10–20 times. On the upper marsh, where the frequency of submergence by astronomical tides is only 3%, Typhoon Paibian led to 4 cm of accretion, accounting for 57% of the net accretion observed over the 2-yr study. Typhoon Paibian led to 4 cm of accretion, accounting for 57% of the net accretion observed over the 2-yr study. Typhoon Paibian and other large storms in the 1990s caused over 50 cm of accretion along the deep axis of the river mouth outlet channel. During calm weather, when hydrodynamic energy was dominated by tides, deposition was centered on the unvegetated flats and lower, marsh with little deposition on the high marsh and erosion in the subtidal channel. Depositional recovery of the tidal flat from typhoon-induced erosion took only several days, whereas recovery of the subtidal channel by erosion took several weeks. A conceptual model for the morphological responses of tidal marshes, flats, and subtidal channels to storms and calm weather is proposed such that sediment continually moves from regions of highest near-bed energy towards areas of lower energy.  相似文献   

Aluminum in the macrotidal Yalujiang estuary: Partitioning of Al along the estuarine gradients and flux   总被引：1，自引：0，他引：1  

H.?Xu  J.?ZhangEmail author  J.?L.?Ren  C.?L.?Liu 《Estuaries and Coasts》2002,25(4):608-621

Water samples were collected from the Yalujiang estuary in both flood periods (August 1992 and August 1994) and dry season (May 1996) and were analyzed for aluminum (Al). Al behaves non-conservatively in the Yalujiang estuary, and a significant loss (70–80%) in dissolved concentration is observed in the upper estuary, in spite of seasonal variation in water discharge and sediment load. About 0.4×10⁶, tons of Al is annually transported from Yalujiang to the estuary, of which the particulate pool clearly dominates. The particulate Al flux through the Yalujiang contributes 35% of the total Al input from Chinese rivers to the Yellow Sea. The data sets from size fractionation and C-18 SPE separation demonstrate that a large fraction of dissolved Al is in colloidal (≈50%) and organically complex (≈60%) forms in the Yalujiang. The observed scavenging from solution to particulate pools in the estuary is most likely through the flocculation of colloidal and organic-complexed Al, which results in a considerable change in dissolved-particulate partitioning, shown by laboratory mixing experiments. Exchange between dissolved and particulate phases is examined by analysis of K_d, the distribution coefficient. The empirical relationship of K_d with chlorinity and suspended matter concentrations was investigated with field observations and model simulations. The model indicated that K_d values of Al are inversely related to the amount of total suspended matter, but K_d-chlorinity plots show different features between dry and flood seasons.  相似文献   

三峡水库初期蓄水对长江口淡水资源的影响   总被引：13，自引：2，他引：13       下载免费PDF全文

曹勇  陈吉余  张二凤  陈沈良  曹卫承 《水科学进展》2006,17(4):554-558

2003年6月1~15日和同年10月20~31日三峡水库进行了初期蓄水。6月份水库蓄水后使下游大通流量减少了37%,长江口的淡水资源的持续时数降低了40%,最大盐度增加了3倍,平均盐度增加了6倍;10月份水库蓄水使大通流量减少了1/2,淡水资源的持续时间呈现下降趋势,最大盐度增加了3倍左右,平均盐度也有类似的表现。再从流量的沿程变化、流量的变化程度、影响河口淡水的持续时间、河口淡水资源影响因子方面进行了讨论,认为三峡蓄水是这两次河口淡水资源减少的主要原因。  相似文献   

长江口岸带冲淤及后备土地资源的沉降效应——以上海崇明东滩为例   总被引：2，自引：0，他引：2  

龚士良  杨世伦 《水文》2007,27(5):78-82

长江口入海泥沙的淤积是上海后备土地资源的重要来源，分析岸带冲淤的演变．有助于对岸带经济圈特别是围垦促淤地区因经济工程活动引发的地面沉降问题的剖析。本文以上海崇明东滩为例，分析30年来的冲淤变化及未来趋势，并据此对新近沉积土的地面沉降效应作简要阐述。  相似文献   

Flow,stress and sediment resuspension in a shallow tidal channel     

Steven traynum  Richard Styles 《Estuaries and Coasts》2007,30(1):94-101

In October of 2004, a 3-d observational program to measure flow and sediment resuspension within a coastal intertidal salt marsh was conducted in the North Inlet/Winyah Bay National Estuarine Research Reserve located near Georgetown, South Carolina. Current and acoustic backscatter profiles were obtained from a moored acoustic Doppler current profiler (ADCP) deployed in a shallow tidal channel during the spring phase of the tidal cycle under high discharge conditions. The channel serves as a conduit between Winyah Bay, a large brackish estuary, and North Inlet, a saline intertidal coastal salt marsh with little freshwater input. Salinity measurements indicate that the water column is vertically well mixed during flood, but becomes vertically stratified during early ebb. The stratification results from brackish (15 psu) Winyah Bay water entering North Inlet via the tidal channel, suggesting an exchange mechanism that permits North Inlet to receive a fraction of the poor water quality and high discharge flow from upland rivers. Although maximum flood currents exceed maximum ebb currents by 0.2 m s⁻¹, suspended sediment concentrations are highest during the latter ebb phase and persist for a longer fraction of the ebb cycle. Even though the channel is flood-dominated, the higher concentrations occurring over a longer fraction of the ebb phase indicate net particulate transport from Winyah Bay to North Inlet during spring tide accompanied by high discharge. Our evidence suggests that the higher concentrations during ebb result from increased bed friction caused by flow asymmetries and variations in water depth in which the highest stresses occur near the end of ebb near low water despite stronger maximum currents during flood.  相似文献   

土壤剖面的磁学特征及其对交通污染的指示意义——以北京首都机场高速公路为例   总被引：4，自引：7，他引：4       下载免费PDF全文

沈明洁  胡守云  U.Blaha  闫海涛  W.R 《第四纪研究》2007,27(6):1113-1120

对北京首都机场高速公路旁采集的土壤柱状T01剖面的磁学参数和金属元素分析,探讨了研究区内现代交通导致的土壤磁学性质的变化及其对环境污染的响应.结果表明,磁参数(χ,ARM和SIRM)与重金属含量呈同步垂向变化趋势.来源于交通运输排放的污染物是土壤剖面上部(0～8 cm)磁性和金属含量增强的主要原因,8cm以下,土壤基本未受到污染,磁性矿物和重金属含量较低,磁性颗粒变化稳定,基本代表了该地区土壤的自然背景.尽管土壤岩石磁学分析表明剖面上下部受污染和未受污染样品的磁载体均是粒度较粗的多畴磁铁矿,但是结合磁参数比值曲线,说明底部样品的磁颗粒的粒度较顶部偏细.磁性矿物的含量变化没有影响磁颗粒的粒度特征.指标聚类等相关分析表明,土壤磁参数(χ,ARM和SIRM)与重金属元素(Pb,Zn和Cu)含量显著相关;结合模糊聚类分析,磁参数可用于追踪、识别交通污染物质在土壤剖面中的富集、迁移状态,揭示不同深度土壤的污染程度.  相似文献   

Characteristics of landscape information Tupu of the Yellow River swings and its subdeltas during 1855―2000     

Ye QingHua  Chen ShenLiang  Huang Chong  Xue YunChuan  Tian GuoLiang  Chen ShuPeng  Shi YaNan  Liu QingSheng  Liu GaoHuan 《中国科学D辑(英文版)》2007,50(10):1566-1577

Based on the theories and methods of cartography on spatial pattern and temporal evolution in Geo-information Tupu (Carto-methodology in Geo-information, CMGI) and the quantitative measurements of pattern and process in landscape ecology, the methodology of landscape information Tupu in studying the swing process of the Yellow River (YR) over the Yellow River Delta (YRD) during 1855―2000 has been demonstrated. The main content includes (1) methodology of landscape information Tupu; (2) evolution process Tupu of YR rump channels; (3) evolution process Tupu of the 7 pieces of subdeltas in YRD during 1855―2000; (4) landscape information Tupu of the modern YRD and the current YRD; (5) landscape information Tupu of YR rump channels on the 7 pieces of subdeltas during 1855―2000; and (6) corridor-matrix landscape information Tupu by YR swings. The methodology of landscape information Tupu here is still primary but we hope that it could provide a new tool for exploring an integrated research on spatiotemporal approaches for landscape "pattern and process".  相似文献   

安徽龙河口水库流域沉积物中粘土矿物分析及其环境意义   总被引：5，自引：0，他引：5  

管章志师育新  戴雪荣陶士康 俞立中 《岩石矿物学杂志》2007,26(1):95-100

龙河口水库是巢湖上游的重要水源地,对水库钻孔ALE的粘土矿物进行定性和半定量分析,发现水库沉积的粘土矿物主要是绿泥石(含绿泥石/蛭石混层矿物),多年平均含量达40%,其次是高岭石和伊利石及少量的蒙皂石,伊利石的多年平均含量只有21%,远低于该流域中晓天河(54%)和滑石河(63.5%)的表层样。水库和龙潭河粘土矿物的含量组成较相似,与晓天河和滑石河差别较大。表层样中粘土矿物的差异主要受流域的地质地貌的影响,水库沉积物中粘土矿物的特征主要与环境动力和粘土矿物的结晶习性有密切的关系。  相似文献   

Application of neural approaches to one-step daily flow forecasting in Portuguese watersheds     

《Journal of Hydrology》2007,332(1-2):1-15

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