不同预处理方法对尕海沉积物粒度测试的影响   总被引：2，自引：0，他引：2  

李华勇  潘安定  明庆忠 《干旱区地理》2011,(4)

湖泊沉积物粒度是研究湖区古环境演化的一个重要代用指标,粒度测量结果与预处理方法密切相关。从柴达木尕海湖岩心钻孔取48个样品,采用五种预处理方法,运用马尔文2000激光粒度仪进行粒度分析。结果显示经过预处理后平均粒径有不同程度的变细。单独加入H2O2除去样品中的有机质后,粒度分散变细最为明显,变幅可达10%左右,单独加入(NaPO3)6或H2O2处理后,>63μm(粗颗粒组分)粒径百分含量降低8个百分点左右。单独加蒸馏水浸泡、单独加HCl除去碳酸盐类胶结物和先后加H2O2、HCl(、NaPO3)6处理这三种方法分散效果不明显。23～33号样品对预处理的灵敏度最差,其他样品灵敏度稍好,但总体上尕海湖沉积物对预处理作用不敏感。对于性质类似的盐湖沉积物粒度测试,本文推荐加H2O2进行预处理。  相似文献   

基于水沙过程的洞庭湖系统功能健康内涵及其表征     

李景保  王建  邓楚雄  帅红 《热带地理》2011,31(2):205-210

洞庭湖与江河相通,其生命的兴衰与水沙过程密切相关.文中将洞庭湖系统视为湖泊系统,探讨洞庭湖系统功能健康内涵及其表征指标体系.研究认为:①洞庭湖是一个由其形态系统功能、生态系统功能和社会经济服务系统功能所构成的有机整体.在这个有机整体中,水沙过程是湖泊系统各项功能之间相互联系的纽带;②水沙过程与湖泊系统功能及其健康状态之...  相似文献   

工程移民的生计变迁与文化适应——以泸沽湖机场移民为例     

赵文娟  崔明昆  沙建 《云南地理环境研究》2011,23(3):7-12

在实地调查和深入访谈的基础上,对泸沽湖机场建设移民搬迁后移民的生计转变、文化调适和社会整合等进行了阐述和分析。研究表明,从高寒山区下移安置到现居地后,移民原有的生计模式、经济结构、饮食习俗和居住格局纷纷被打破重构,同时还面临家支血缘关系网络解体、宗教信仰和观念淡化以及精神文化缺失等社会和心理方面的冲击与挑战。相关研究应加强对移民文化变迁、社会适应和心理认同的关注,从人本出发促进移民地区的文化融合与和谐发展。  相似文献   

风险管理视角下鄱阳湖流域暴雨洪涝灾害防御对策与建议          下载免费PDF全文

王海亮  王阳  敬雨男  袁婧 《气象与减灾研究》2018,41(4):304-309

分析了鄱阳湖流域暴雨洪涝灾害分布情况,指出暴雨洪涝灾害防御在组织体系、部门联动、风险区划、防御规划、人员队伍、预警发布、灾防意识等方面存在的不足,最后提出了开展风险评估、制定防御规划、修订应急预案、健全法规体系、落实工程措施、完善组织体系、建立专业队伍、加强预警发布、构建联动机制、做好风险转移、开展科普宣传等针对性的改进措施和建议。  相似文献   

Major and trace element geochemistry of Lake Bogoria and Lake Nakuru,Kenya, during extreme draught     

Franz Jirsa  Martin Gruber  Anja Stojanovic  Steve Odour Omondi  Dieter Mader  Wilfried Körner  Michael Schagerl 《Chemie der Erde / Geochemistry》2013

The physico-chemical properties of water samples from the two athalassic endorheic lakes Bogoria and Nakuru in Kenya were analysed. Surface water samples were taken between July 2008 and October 2009 in weekly intervals from each lake. The following parameters were determined: pH, salinity, electric conductivity, dissolved organic carbon (DOC), the major cations (FAAS and ICP-OES) and the major anions (IC), as well as certain trace elements (ICP-OES). Samples of superficial sediments were taken in October 2009 and examined using Instrumental Neutron Activation Analysis (INAA) for their major and trace element content including rare earth elements (REE). Both lakes are highly alkaline with a dominance of Na > K > Si > Ca in cations and HCO₃ > CO₃ > Cl > F > SO₄ in anions. Both lakes also exhibited high concentrations of Mo, As and fluoride. Due to an extreme draught from March to October 2009, the water level of Lake Nakuru dropped significantly. This created drastic evapoconcentration, with the total salinity rising from about 20‰ up to 63‰. Most parameters (DOC, Na, K, Ca, F, Mo and As) increased with falling water levels. A clear change in the quality of DOC was observed, followed by an almost complete depletion of dissolved Fe from the water phase. In Lake Bogoria the evapoconcentration effects were less pronounced (total salinity changed from about 40‰ to 48‰). The distributions of REE in the superficial sediments of Lake Nakuru and Lake Bogoria are presented here for the first time. The results show a high abundance of the REE and a very distinct Eu depletion of Eu/Eu* = 0.33–0.45.  相似文献   

长江水氢、氧同位素组成的时空变化及其环境意义   总被引：6，自引：0，他引：6  

丁悌平  高建飞  石国钰  陈峰  罗续荣  王成玉  韩丹 《地质学报》2013,87(5):661-676

在2003～2007年间,在长江干流的25个水文站及主要支流的13个水文站系统采样,进行了氢氧同位素研究。观测到的D变化范围为-30‰～-112‰,变化范围为-3.8‰～-15.4‰。从长江源头到河口,不同时期的样品均显示相同的氢氧同位素沿程变化特征。从源头到攀枝花,长江干流的D与逐步下降;而由攀枝花到入海口,D与值逐渐升高。 研究发现,控制长江水的氢氧同位素组成的主要因素是大气降水。长江干流D与值所展现的从攀枝花至河口逐渐升高的趋势就是对流域大气降水的D与变化趋势的响应。长江各支流在氢氧同位素组成上的差别及其对干流的影响也反映大气降水对长江水的制约。 蒸发作用对长江水的氢氧同位素组成也有重要影响。长江源头地处青藏高原,高原湖泊和沼泽星罗棋布。由于气候干燥、日照强烈,湖沼水经过长期的蒸发,盐度逐渐加大,D和18O值也逐渐升高。这些湖水的加入对长江水的氢氧同位素组成也造成一定影响。蒸发作用在枯水期也使洞庭湖与鄱阳湖的D和18O值升高,进而提高长江相关河段的D和18O值。 冰雪融化是影响长江水的氢氧同位素组成的另一重要因素。在长江源头和所有左岸支流的源头,冰川融雪都是重要的水源之一。由于冰川水在氢氧同位素组成上的特殊性,其对河水贡献的大小将影响河水的氢氧同位素组成。 三峡大坝对于长江的水动力体系影响巨大,三峡水库对长江水资源的调控作用有待长期观测研究。从本次的研究资料来看,三峡大坝在丰水期对相应河段的氢氧同位素变化趋势影响不大。但在枯水季节,三峡水库蓄水使下游的宜昌和沙市的水源发生明显变化,导致D和18O值的显著降低。 长江水资源状况及其演变趋势是受到各方面高度关注的重要研究课题。为深入探讨这一问题,需要了解长江水资源的变化与各种气象与水文要素之间的关系,查明大气降水、地下水、冰川水、湖水与河水之间的交互作用。而氢氧同位素示踪技术在这方面可以发挥关键性的作用。由于现有资料有限,目前还无法利用氢氧同位素组成来追溯其气候条件的详细演化过程。但若能在进行系统水文测量的同时,适当开展氢氧同位素测定,将对研究长江水资源状况及其演变趋势大有脾益。  相似文献   

Holocene sedimentary environments in Lake Eyre,South Australia     

J. A. Dulhunty 《Australian Journal of Earth Sciences》2013,60(3-4):437-442

In late Pleistocene time Lake Dieri (ancestral ‘Greater Lake Eyre') was permanently filled during a wet climatic phase. Towards the close of Pleistocene time the watertable fell, Lake Dieri dried up, and its sediments deflated. Later the watertable rose, establishing ephemeral Lake Eyre in the deflated area, and Holocene sedimentation commenced. At about this time Lake Eyre tilted to the south and three sedimentary environments developed: (1) a saline playa environment without saltcrusts in the northern end of the lake, where water drains away before wholly evaporating; (2) a terminal salina environment in the south end, where evaporation of brines leaves saltcrusts overlying gypseous sediments; and (3) a saline flocculation environment between the playa and salina environments, where sediments are deposited by flocculation when muddy floodwater from the north meets highly saline water of the southern salina.

In the northern playa environment, sedimentation is limited to the top of the capillary fringe above the watertable, below which sediments remain moist and protected from aeolian erosion, but above which they dry and blow out of the lake. In the southern salina environment sedimentation has not kept pace with the Holocene rise in watertable. If and when it does reach such a level, downward leaching of salt and deflation of exposed sediments is likely to occur. In the flocculation environment new deposits of clay are added but kept permanently wet by rising groundwater. When flocculated sediment builds too high, its excess is transferrred by surface water into the salina deposits to the south.  相似文献   

Diatoms and ostracods as mid-Holocene palaeoenvironmental indicators,North Stromatolite Lake,Coorong National Park,South Australia ∗     

S. Edwards  Y. Bone  P. A. Gell  V. A. Gostin 《Australian Journal of Earth Sciences》2013,60(4):651-663

The Holocene carbonate sequence of perennial North Stromatolite Lake, located adjacent to the Coorong Lagoon near Salt Creek, South Australia, includes a prominent sapropelic unit (7 – 12% total organic carbon), in places more than 2 m thick, that was sampled for the purpose of radiocarbon dating and documenting its diatom and ostracod biostratigraphy. The recovered ostracods were also subjected to carbon and oxygen isotopic analysis. The bulk organic matter at the base of the sapropel yielded an uncalibrated ¹⁴C age of 6080 ± 60 y BP. Diatoms, where preserved, are almost exclusively benthic. Stratigraphic variation of the proportions of key indicator species in diatom assemblages records a marked oscillation between oligosaline and eusaline conditions in the hypolimnion during deposition of the sapropel. Ostracod carbon isotope data indicate that the lake at this time was eutrophic, thereby enriching the dissolved inorganic carbon of the hypolimnion in ¹³C. However, the observed secular variation in δ¹³C implies a mid-sapropel drop in productivity, caused by a freshening of the lake. Ostracod δ¹⁸O values display an overall increase through the sapropel consistent with the rising salinity of the hypolimnion. The existence of a flourishing benthic ostracod community, together with the valve ornamentation of Osticythere baragwanathi, indicates that the bottom waters were well oxygenated. Thus, anoxia was not a prerequisite for sapropel accumulation. The biostratigraphy and chemostratigraphy of the sapropel concur in suggesting a lack of climatic uniformity during its deposition, a period of ～1200 years. This study therefore highlights the potential of diatoms and ostracods in shallow perennial alkaline lakes along the Coorong coastal plain as proxies for short-term (10² – 10³ years) Holocene palaeoenvironmental change in southeastern Australia.  相似文献   

Early Devonian synorogenic alluvial-fan deposits of the Maccullochs Range,western New South Wales     

G. Neef 《Australian Journal of Earth Sciences》2013,60(5):647-660

The Early Devonian, Maccullochs Range beds (new) of the Winduck Interval largely comprise non-marine fine-grained sheet-flood-deposited sandstones which lie in the southeast sector of the Darling Basin Conjugate Fault System. Deposition of the >2.5 km-thick sequence occurred on the Wilcannia, Towers and Coolabah Bore alluvial fans, that were sourced largely from lightly indurated sandstone caps overlying a large basement high lying north of the Darling River Lineament, and also from west of Maccullochs Range (Coolabah Bore Fan). Four lithofacies are recognised. Lithofacies 1, massive sandstone, is proximal and was deposited from hyperconcentrated sheet floods. The more distal lithofacies 2 is partly massive, partly laminated and partly affected by soft sediment slumping during its deposition. It contains 1.3 – 3.5 m-thick sheet-flood successions that rarely show cross-bedding. Lithofacies 3 and 4 are minor: lithofacies 3, stream-flood deposited, comprises coarse-grained, pebbly sandstone and lithofacies 4, transient playa lake deposits that are locally intercalated with lithofacies 2. In lithofacies 2, thick massive fine-grained sandstone is commonly overlain by laminated sandstone that was deformed when soft. Incised channel deposits in lithofacies 2 deposits are rare and palaeosols were not discovered. Permanency of the positions of two of the alluvial fans, and by inference their feeder streams, remained unchanged for ～9 million years. The fans overlie probable floodplain deposits observed in a quarry in the easternmost part of the study area. Marine fossils are very minor in the range—the brachiopod Howellella jaqueti at one locality indicates an Early Devonian age for one of the brief marine incursions into what was normally an alluvial-fan environment. Very brief marine incursions elsewhere in the group are deduced from the presence of very rare fossil gastropods.  相似文献   

Lake George revisited: New evidence for the origin and evolution of a large closed lake,Southern Tablelands,NSW, Australia     

M. Macphail  L. K. Fifield  B. Pillans  M. Davies  G. Hope 《Australian Journal of Earth Sciences》2013,60(7):853-871

Lake George contains the longest continuous sedimentary record of any Australian lake basin, but previous age models are equivocal, particularly for the oldest (pre-Quaternary) part of the record. We have applied a combination of cosmogenic nuclide burial dating, magnetostratigraphy and biostratigraphy to determine the age of the basal (fluvial) unit in the basin, the Gearys Gap Formation. Within the differing resolutions achievable by the three dating techniques, our results show that (i) the Gearys Gap Formation, began accumulating at ca 4 Ma, in the early Pliocene (Zanclean), and (ii) deposition had ceased by ca 3 Ma, in the mid late Pliocene (Piacenzian). Whether the same age control provides an early Pliocene (Zanclean) age for the formation of the lake basin is uncertain. During the Piacenzian, the vegetation at the core site was a wetland community dominated by members of the coral fern family Gleicheniaceae, while the surrounding dryland vegetation was a mix of sclerophyll and temperate rainforest communities, with the latter including trees and shrubs now endemic to New Guinea–New Caledonia and Tasmania. Mean annual rainfall and temperatures are inferred to have been ～2000–3000 mm, although probably not uniformly distributed throughout the year, and within the mesotherm range (>14°C <20°C), respectively. Unresolved issues are: (1) Does the basal gravel unit predate uplift of the Lake George Range and therefore provide evidence that one of the proposed paleo-spillways of Lake George, that above Geary's Gap, has been elevated up to 100–200 m by neotectonic activity over the past 4 million years? (2) Did a shallow to deepwater lake exist elsewhere in the lake basin during the Pliocene?  相似文献