普若岗日冰原西侧冰前风沙地貌的形成与我国冰川型沙漠的发现

在青藏高原中央、普若岗日冰原西侧流石坡地带山麓面上,分布有约100 km²的由戈壁与沙丘组成的地貌,这是世界罕见的、也是我国发现的首例中纬度、高海拔地区冰前沙漠沉积。野外地貌、地层测量和室内样品的粒度、矿物、¹⁴C测年分析等结果表明,其形成时代约为16 ka BP以来;沉积特征在沙丘沉积序列中表现为风成砂夹零星腐殖质层,在戈壁中表现为砾石表面具次生方解石或碳酸钙沉淀层;演化模式为冷直线式;形成条件为以下伏冰碛物为主要砂源,以行星西风环流和高原冬季风引起的地面西风为主要动力,以持续的寒冷半干旱为气候背景;成因主要与冰原西缘冰川作用形成丰富的冰碛物砂源有关;因此,这类沙漠与一般冰缘沙漠以河湖相砂为源具有显著区别,可称为"冰川型沙漠"。由于其形成兼与冰原、气候和环流的变化密切相关,所以它是高原腹地全新世气候环境变化的重要记录。     

Proglacial Sediment—Landform Associations of a Polythermal Glacier: Storglaciären, Northern Sweden

Mapping and laboratory analysis of the sediment—landform associations in the proglacial area of polythermal Storglaciären, Tarfala, northern Sweden, reveal six distinct lithofacies. Sandy gravel, silty gravel, massive sand and silty sand are interpreted as glaciofluvial in origin. A variable, pervasively deformed to massive clast‐rich sandy diamicton is interpreted as the product of an actively deforming subglacial till layer. Massive block gravels, comprising two distinctive moraine ridges, reflect supraglacial sedimentation and ice‐marginal and subglacial reworking of heterogeneous proglacial sediments during the Little Ice Age and an earlier more extensive advance. Visual estimation of the relative abundance of these lithofacies suggests that the sandy gravel lithofacies is of the most volumetric importance, followed by the diamicton and block gravels. Sedimentological analysis suggests that the role of a deforming basal till layer has been the dominant factor controlling glacier flow throughout the Little Ice Age, punctuated by shorter (warmer and wetter climatic) periods where high water pressures may have played a more important role. These results contribute to the database that facilitates discrimination of past glacier thermal regimes and dynamics in areas that are no longer glacierized, as well as older glaciations in the geological record.     

Artificial Neural Networks in Proglacial Discharge Simulation: Application and Efficiency Analysis in Comparison to the Multivariate Regression; A Case Study of Waldemar River (Svalbard)

Artificial neural networks were applied to simulate runoff from the glacierized part of the Waldemar River catchment (Svalbard) based on hydrometeorological data collected in the summer seasons of 2010, 2011 and 2012. Continuous discharge monitoring was performed at about 1 km from the glacier snout, in the place where the river leaves the marginal zone. Averaged daily values of discharge and selected meteorological variables in a number of combinations were used to create several models based on the feed‐forward multilayer perceptron architecture. Due to specific conditions of melt water storing and releasing, two groups of models were established: the first is based on meteorological inputs only, while second includes the preceding day's mean discharge. Analysis of the multilayer perceptron simulation performance was done in comparison to the other black‐box model type, a multivariate regression method based on the following efficiency criteria: coefficient of determination (R²) and its adjusted form (adj. R²), weighted coefficient of determination (wR²), Nash–Sutcliffe coefficient of efficiency, mean absolute error, and error analysis. Moreover, the predictors' importance analysis for both multilayer perceptron and multivariate regression models was done. The performed study showed that the nonlinear estimation realized by the multilayer perceptron gives more accurate results than the multivariate regression approach in both groups of models.     

Analyzing Slug Tests in Wells Screened Across the Watertable: A Field Assessment

The slug test is the most widely used technique for the in situ estimation of hydraulic conductivityin confined and unconfined formations. Currently, there are no generally accepted methods in thegroundwater literature for the analysis of response data from slug tests performed in wells screenedacross the watertable. A field study was undertaken in an attempt to develop a set of practicalguidelines for tests conducted in such wells. Three wells, screened within unconsolidated materialexhibiting a range of hydraulic conductivities (.05–30.0 m/day), were installed to depths of up to9 m (30 ft) in Kansas River alluvium that ranges in thickness from 15 m to 21 m (50 ft to 70 ft)near Lawrence, Kansas. Intensive well-development efforts removed any drilling debris that couldinterfere with well-formation hydraulics. Once the wells were developed properly, a series of slugtests was performed at each well. The tests were designed to assess the role of the unsaturatedzone and the appropriateness of assuming a fixed hydraulic head upper boundary. The results ofthis investigation can be summarized as follows: (1) the sufficiency of well development shouldbe based on repeat slug tests and not the clarity of pumped water; (2) the effective screen radiusfor best model analysis should be based on a mass balance and not nominal screen dimensions;(3) the watertable can be represented as a constant head boundary and flow in the unsaturatedzone can be ignored in most situations; (4) conventional techniques for the analysis of slug-testdata seem to be reasonable for slug tests conducted in wells screened across the watertable, whenused with the appropriate effective screen radius and normalized head range; and (5) fluctuationsin the watertable elevation through time can be exploited to obtain some insight into the natureof vertical variation in hydraulic conductivity at a well. The results of this investigation indicatethat multiple slug tests should be performed at wells screened across the watertable in order toreliably assess the sufficiency of well development and the appropriateness of conventional theory.     

A comparison of annual and seasonal carbon dioxide effluxes between sub-Arctic Sweden and High-Arctic Svalbard

Recent climate change predictions suggest altered patterns of winter precipitation across the Arctic. It has been suggested that the presence, timing and quantity of snow all affect microbial activity, thus influencing CO₂ production in soil. In this study annual and seasonal emissions of CO₂ were estimated in High-Arctic Adventdalen, Svalbard, and sub-Arctic Latnjajaure, Sweden, using a new trace gas-based method to track real-time diffusion rates through the snow. Summer measurements from snow-free soils were made using a chamber-based method. Measurements were obtained from different snow regimes in order to evaluate the effect of snow depth on winter CO₂ effluxes. Total annual emissions of CO₂ from the sub-Arctic site (0.662–1.487 kg CO₂ m^–2 yr^–1) were found to be more than double the emissions from the High-Arctic site (0.369–0.591 kg CO₂ m^–2 yr^–1). There were no significant differences in winter effluxes between snow regimes or vegetation types, indicating that spatial variability in winter soil CO₂ effluxes are not directly linked to snow cover thickness or soil temperatures. Total winter emissions (0.004–0.248 kg CO₂ m^–2) were found to be in the lower range of those previously described in the literature. Winter emissions varied in their contribution to total annual production between 1 and 18%. Artificial snow drifts shortened the snow-free period by 2 weeks and decreased the annual CO₂ emission by up to 20%. This study suggests that future shifts in vegetation zones may increase soil respiration from Arctic tundra regions.     

粘性泥石流复式沟床水力特性探讨

天然粘性泥石流沟床都是复式断面，不同滩槽宽度比在不同的泥位条件下其水力要素（过流面积、湿周、水力半径）有所不同。引用天然河流水力计算方法，对概化的复式沟床泥石流流量计算表明：滩槽宽度比对滩、槽过流能力及流量分配有较大的影响；同一滩槽比情况下，主槽过流与全断面过流量之比随泥深增大而逐渐减小，而滩面过流与全断面过流量之比却逐渐增大；泥石流复式沟床滩槽影响可用协同度表示，计算分析表明，滩槽比相同时，随泥深增加，滩、槽影响逐渐减小。     

基于PTFs的干旱地区土壤饱和导水率的尺度扩展

土壤饱和导水率的空间分布是流域水文模拟及溶质运移研究的先决条件.基于塔里木河干流108个剖面的土壤质地、有机质及容重等测试数据,运用4种土壤传递函数(PTFs)进行土壤饱和导水率预测与检验,分析土壤饱和导水率的空间变异性并计算合理采样数量,并通过尺度上推的方法预测流域尺度土壤水力参数的空间分布特征.结果表明:Campbell模型为4种PTFs模型中最适合本研究区的土壤传递函数.从空间分布的预测结果来看,不同层土壤饱和导水率的分布特征具有相似性,而深层土壤饱和导水率大于浅层.     

中国县域城镇化的空间特征与形成机理

本文综合运用样带、地统计、地理探测器等多种研究方法, 分析了1990 年以来中国县域城镇化的时空特征及形成机理。研究表明:①中国县域城镇化水平时空动态的差异特征显著, 北方边境县域高城镇化和东部沿海县域高城镇化形成的“人字形”空间形态逐渐凸显;以武汉都市圈为中心的两湖地区、成渝地区、关中—天水经济区的县域城镇化水平提升较快, 西南地区、青藏高原地区保持较低的城镇化水平;②2000 年以来中国县域城镇化水平及其变化速度的区域差异逐渐缩小, 陇海兰新线、长江沿线、北方边境、106 国道、东部沿海样带县域城镇化差异明显;县域经济发展阶段、固定资产投资、离中心城市距离、二三产业水平、农民人均纯收入、人口密度是影响县域城镇化空间分异的主要因素, 同时粮食生产主导定位、非农业人口统计口径、城镇设置标准等因素也影响县域城镇化水平及发展过程。未来城镇化发展应遵循地域差异, 凸显主导功能, 推进优化与重点发展区的集约型城镇化、耕地与粮食主产区的分流型城镇化、生态与水源保护区的迁移型城镇化, 以及园区与城镇近郊区的融入型城镇化, 实现城乡土地资源集约利用, 促进城镇化进程中人—地—业耦合与协调发展。     

西北干旱区间歇性河流与含水层水量交换研究进展与展望

本文依托国家自然科学基金青年项目“河水温度对干旱区宽浅型河床渗透系数影响的定量研究”,并梳理了其他相关研究,总结了中国西北干旱区间歇性河流与含水层水量交换研究所面临的基础科学问题及当前所取得的研究进展。主要结论为：以宽浅型沙质河床为基本特征的西北干旱区内陆河流域下游河流,其河床每年经历数次干湿交替与冻融过程。受河水温度与河流水动力条件的影响,河床作为河流与含水层相互作用的重要界面,其渗透性能具有高度时空变异性,已成为河水与地下水水量交换研究的难点与热点。分析指出,在环境变化和当前交叉学科迅猛发展的背景下,以河流与含水层相互作用为核心的潜流带水文学发展面临新的机遇与挑战。     

Effect of a Mobile Fine Fraction on Slug Test Results

In recent slug testing at our field site there seemed to be a dependence on flow direction and initial slug height in some of the results for hydraulic conductivity that could not be explained by any known models. At first, we thought the dependence on flow direction and initial height was the result of slug length and friction in the annular space between the slug and casing. Later slug testing with a packer eliminated the effect of the slug in the wellbore, but the initial head and directional dependence observed earlier remained for the packer data. This indicated possible well development problems, so a program of well development was instituted and slug tests were performed at various points in this program. We were not able to eliminate the head and directional dependence of the results for the hydraulic conductivity by well development. However, we have arrived at some conclusions that may be helpful to others interpreting slug test data in aquifers with a mobile fine fraction. It seems that well development and slug testing can cause fine material to be redistributed in an aquifer. Apparently in our slug testing and development program, we have created an artificial distribution of fine material that differs with radius, causing the apparent hydraulic conductivity to differ with volume injected or withdrawn. Directional dependence may be caused by the water moving away from the well carrying fines, resulting in a build up of fine material at some radius and a lower apparent hydraulic conductivity.     

Soil physical properties change in the process of oasisization

Oasisization is a process of converting a natural desert into a man-made oasis in order to satisfy social needs under certain economical and technical conditions. This paper substitutes space for time in order to study physical property changes of oasis soil along the oasisization in about a 1,000-year period. This research focuses on providing the bases for better understanding the process of oasisization. The results show: (1) In about 1,000-year chronological scale, the bulk density and the saturated soil hydraulic conductivity of the surface layer (0-20 cm) significantly reduced with the increase of land reclamation time, while soil porosity, stability of aggregates, and silt content significantly increased. The soil bulk density of the unreclaimed filed (0 year) and the reclaimed field (about 1,000 years) in the surface layer (0-20 cm) are 1.51 g/cm3 and 1.35 g/cm3, the total porosity are 43.16% and 49.27%, the capillary porosity are 38.73% and 47.10%, the water-stable aggregate (0.25 mm) content are 24.60% and 49.59%, the sand content are 85.42% and 61.56%, the clay content are 3.93% and 4.80%, the specific surface area are 128 cm2/g and 231 cm2/g, and the saturated hydraulic conductivity are 0.74 cm/h and 0.34 cm/h, respectively. (2) In the first 30 years of the oasis reclamation, the changes are relatively fast, and the rates of the saturated soil hydraulic conductivity, dry aggregate (0.25 mm), water-stable aggregate (0.25 mm) content, and specific surface area are 0.01 cm/h·yr, 0.58%/yr, 0.50%/yr, and 1.48 cm2/g yr, respectively.     

Characteristics of near-surface electrokinetic coupling

Naturally occurring electric potentials at the Earth's surface are traditionally studied using self-potential geophysics. Recent theoretical and experimental work has reinvestigated the manner in which the measurement can be made dynamically using a pressure source. The methodology, often referred to as seismoelectric, relies on electrokinetic coupling at interfaces in the streaming potential coefficient. The ultimate aim of the developing methodologies lies in the detection of zones of high fluid mobility (permeability) and fluid geochemical contrasts within the subsurface. As yet there are no standard methods of recording and interpretation: the technique remains experimental. Field measurements are made using a seismic source and by recording electric voltage across arrays of surface dipoles. This study presents observational characteristics of electrokinetic coupling based on experiments carried out in a wide range of environments. Theory concerning the coupled elastic and electromagnetic wave equations in a saturated porous medium is discussed. It is predicted that coupling will produce electromagnetic radiation patterns from vertical electric dipoles generated at interfaces. Surface- and body-wave coupling mechanisms should provide different time–distance patterns. Vertical electric dipole radiation sources are modelled and their spatial characteristics presented. A variety of experimental configurations have been used, and geometries that exploit phase asymmetry to enhance the separation of signal and noise are emphasized. The main experimental results presented are detailed observations in the immediate vicinity of the source. Simultaneous arrivals across arrays of surface dipoles are not common. The majority of such experiments have indicated that shot-symmetric voltages which display low-velocity moveout are the dominant received waveforms.     

大克泊湖床垂向渗透系数试验研究

湖床渗透系数是地下水与湖水关系研究中的重要参数之一,是评价湖水与地下水定量转化关系的基础。以鄂尔多斯盆地大克泊湖为例,首先分析了湖床沉积物的颗粒组成,然后利用现场渗透试验技术进行了野外试验,计算了湖床的垂向渗透系数。计算结果表明,各测点的平均垂向渗透系数介于2.02×10-1～1.103 cm/d,最大值是最小值的4倍,表明大克泊湖床的垂向渗透性能在空间具有非均质性。湖床沉积物垂向渗透系数的数量级表明,湖水很难和地下水直接发生交换,地下水主要以溢流的形式补给湖水。因此,在枯水季节,地下水无法补给湖水,导致大克泊湖的面积在蒸发作用下萎缩迅速。颗粒分析结果表明,湖床沉积物以粘土为主,根据湖区的地层岩性分析,其主要来自环河组中泥岩的风化。     

绿洲化过程中绿洲土壤物理性质变化研究

绿洲化是指在一定的经济、技术条件下,为满足社会需求,把原生荒漠改造成人工绿洲的过程。利用空间代替时间的方法研究了约1 000 a来随着绿洲化进程绿洲土壤物理性质的变化过程,旨在为深入认识绿洲化过程提供依据。结果表明:①在约1 000 a的时间尺度上,随绿洲土壤开垦年限的增加,表层（0～20 cm）土壤容重与饱和水力传导度随时间显著降低,与此同时,土壤孔隙度、团聚体稳定性、粉粒含量显著增加。未开垦（0 a）和开垦约1 000 a表层土壤容重分别为1.51 g·cm-3、1.35 g·cm-3,总孔隙度为43.16%、49.27%,毛管孔隙度为38.73%、47.10%,>0.25 mm水稳性团聚体含量为24.60%、49.59%,沙粒含量为85.42%、61.56%,粘粒含量为3.93%、4.80%,土壤比表面积为128 cm2·g-1、231 cm2·g-1,土壤饱和水力传导度为0.74 cm·h-1、0.34 cm·h-1。②绿洲土壤在开垦的最初30 a间土壤饱和水力传导度、>0.25 mm干团聚体、>0.25 mm水稳性团聚体、比表面积变化相对较快,分别为0.01 cm·h-1·a-1、0.58%·a-1、0.50%·a-1、1.48 cm2·g-1·a-1。     

云南气象灾害特征及成因分析

用1950~1999年气象灾害资料,分析云南气象灾害的主要特征,具有种类多、频率高、重叠交错;分布广、季节性、区域性突出;成灾面积小、累积损失大的特征。指出地理环境、气候、人类活动是形成云南气象灾害的主要原因。特殊的低纬高原、邻近热带海洋、地形地貌复杂、山高坡陡、植被少、降雨集中、地质构造复杂、断裂活动强烈是形成云南气象灾害的地理环境因素。季风强弱与冬夏大气环流差异是决定云南气象灾害的主要气候背景。人口剧增,垦植过度,滥伐森林,水土流失严重指出是加剧云南气象灾害频繁发生和损失严重的主要人为因素,提出了云南气象灾害的防灾减灾对策。     

高寒草甸草地退化对土壤水热性质的影响及其环境效应

青藏高原高寒草甸草地的大面积退化,将改变浅层土壤的水热性质,影响地表水热交换,甚至导致区域生态环境的变化。本文通过系统分析典型原生高寒草甸与中度退化高寒草甸的植物群落特征、地上地下生物量和土壤理化特征的差异,研究高寒草甸草地退化对土壤水热性质的影响及其环境效应。结果表明:随着高寒草甸草地退化,植被覆盖度显著降低(p<0.01),适应旱生、深根系的杂草侵入适应湿润生境、浅根系的以莎草科植物为主的原生植被,生物多样性显著增加(p<0.01);草毡表层(0～10 cm)地下生物量显著减少(p<0.01),30～50 cm地下生物量显著增加(p<0.01)。草毡表层变薄降低了土壤容重的垂向异质性,使表层土壤容重显著增加(p<0.01),土壤颗粒显著变粗(p<0.01)。受浅层土壤有机质降低和土壤容重增加的影响,中度退化高寒草甸土壤的持水量和饱和导水率降低,土壤导热率升高。高寒草甸草地植被退化,土壤持水量、饱和导水率降低和导热率增加将加速地表水热交换,对高寒草甸草地退化和下伏多年冻土消融都可能是正反馈。     

湘西洪江古商城的特点、形成及其开发利用和保护

湘西洪江古商城,凭借其特有的交通区位优势,历史上曾一度成为久负盛名的西南地区商品转口贸易城市,集经济、政治、军事、宗教、文化功能于一体的综合性城市和具有鲜明地域特色的立体式山水型城市,是明清以来祖国大西南特定区域自然地理环境与社会经济环境综合影响的结果,其作为以完整风貌保存下来的中世纪专业性商城,在国内具有唯一性,应该妥善加以保护和合理利用。     

From Micro to Meso: an exercise in determining hydraulic conductivity of fractured sandstone cores from detailed characterization of the fractures

Hydraulic conductivities of fractured sandstone bore cores of 0.1 m in diameter are calculated using detailed characterization of the fracture geometry parameters determined using a resin casting technique. The accuracy of the measurements was about  0.25–1.25 μm  with the image size used. The values of the effective fracture apertures vary between 10 μm and 50 μm. For modelling purposes the samples are sectioned serially, perpendicular to the flow direction along the cylinder axis. The hydraulic conductivity of individual slices is estimated by summing the contribution of the matrix (assumed uniform) and each fracture (depending on its length and aperture). Finally, the hydraulic conductivity of the bulk sample is estimated by a harmonic average in series along the flow path. Results of this geometrical upscaling compare favourably with actual conductivity measured in hydraulic and pneumatic experiments carried out prior to sectioning. This study shows that the determination of larger-scale conductivity can be achieved, based on the evaluation of fracture geometry parameters (e.g. fracture aperture, fracture width and fracture length), measured using an optical method, at least at the laboratory scale.     

战后日本土地价格的变化特点及其成因分析

战后,日本的土地价格持续上涨,出现所谓“土地必定升值”的土地神话。特别是在80年代中后期的地价高涨中,以东京为首的几个大城市区域的地价一下子上涨了数倍之多。但是90年代初地价开始暴落,长期流行的土地神话终于沉寂。本文从地理学的角度出发,考察研究日本战后土地价格发展变化的时空分布特点,并分析探讨各种要素对地价涨落及其时空分布特点形成的影响。