Impact of fractional vegetation cover change on soil erosion in Miyun reservoir basin,China

It is well known that soil erosion at the watershed scale is the result of interactions between various factors. Among these environmental factors, vegetation is the most important and plays a major role in the soil erosion process. The impact of fractional vegetation cover change (FVCC) on soil erosion in non-contributing areas is a heavily discussed topic. In this paper, the fractional vegetation cover (FVC) in 2002 and 2005 was calculated by using a backpropagation neural network based on remote sensing (RS) data. Then the impacts of FVCC on sediment loads at the outlets of two Miyun reservoir sub-basins were evaluated by integrating RS and geographic information system with statistical analysis. The Miyun reservoir basin (MRB) is characterized by hilly and mountainous topographies and seasonal rainy weather. The primary goal of this paper is to gain a better understanding of FVCC, its driving forces, and its impact on regional soil erosion. We discuss spatiotemporal variations in precipitation and soil erosion, identify which factors contribute to those variations, analyze the influences of FVCC on climate change and human activities and, finally, conclude that changes in FVC and climate regimes are primary factors for soil erosion in MRB. We also discuss how sediment loads may be used to quantitatively separate biophysical and anthropogenic influences and to identify critical thresholds that might have dramatic consequences for the watershed ecosystem. These findings should be quite helpful for sensible watershed development and management planning.     

Thaw-induced slope failures and susceptibility mapping in permafrost regions of the Qinghai–Tibet Engineering Corridor,China

With recent climatic warming and enhanced human activities, slope failures related to permafrost degradation are widespread along the Qinghai–Tibet Engineering Corridor. Assessment and mapping of the slope failures are necessary to mitigate hazards and plan engineering activities. According to our field investigations, the occurrence of slope failures is mainly controlled by the slope gradient, ground-ice content, permafrost temperatures, surficial deposits, and slope aspect. Modeling conducted in ArcGIS? was used to produce a slope failure susceptibility map for a representative region along the Qinghai–Tibet Railway from Wudaoliang to Fenghuo Mountain Pass. The study region was divided into four classes based on slope failure susceptibility: (1) unlikely, (2) low, (3) moderate, and (4) high. Areas classified as unlikely accounted for 10.76 % of the study region, while low susceptibility areas comprised 44.51 %. The moderate and high susceptibility zones comprised 21.79 and 22.94 %, respectively. The actual distribution of slope failures in the region was consistent with the modeled results, which demonstrates the utility of the assessment method for future hazard management and engineering planning.     

阳泉市五十年气候变化研究

利用阳泉市气象观测站1955年～2004年的月平均气温、日照时数、旬降水量、暴雨日数、蒸发量等资料,对阳泉市50a来特别是近10a的气候变化作了较为全面的分析。结果表明:阳泉市50a来降水呈下降趋势(-35.8mm/10a),气温呈上升趋势(0.2℃/10a),日照时数变化呈减少趋势。     

合水地区长6油层微观渗流特征及驱油效率影响因素研究

对鄂尔多斯盆地合水地区长6油层组超低渗透储层的微观渗流特征及驱油效率影响因素进行深入研究,为提高采收率提供了科学依据。研究以真实砂岩微观模型渗流实验为主要手段,结合铸体薄片、扫描电镜、压汞等方法对孔隙结构、岩石类型等进行测试。研究表明,研究区长6油层的渗流特征以网状驱替和均匀驱替为主,指状驱替甚少;不同的驱替类型对应不同的最终驱油效率,均匀驱替模型最终驱油效率最高,指状驱替模型最低。储层物性中渗透率是影响驱油效率的主要因素,孔隙度次之;适当地提高驱替压力能够有效地提高驱油效率;提高注水体积倍数也能适当地提高驱油效率;非均质性对驱油效率也有一定的影响。     

Study on the ore-forming and ore-controlling structure of the Mujicun Cu (Mo) ore deposit, Hebei Province, China

The Mujicun Cu (Mo) ore deposit at Laiyuan, Hebei Province, is a currently proven large-sized Cu (Mo) polymetallic ore deposit and it is located in the second-ordered fault depression basin of the ditachment belt on the hanging-wall on the western side at the juncture of the Laiyuan dumbell-shaped complex in the northern part of the Fuping mantle-branch structure. Metallogenesis is controlled by diorite porphyrite in intrusive relation with the fault depression basin and other relevant fault structure systems and intenstive wall-rock alteration zones. This study, in conjunction with the most recent exploration data, analyzed the geological background of metallogenesis of this deposit, summaried the geological characteristics of typical ore deposits, determined the alteration zonation of the deposit, investigated regional metallogenesis and the genesis of typical ore deposits, discussed the regional ore-forming and ore-controlling structures, and generalized the regional ore-controlling model and metallogenic model of the deposit. It is considered that the Mujicun porphry Cu (Mo) deposit, the Tieling, Futuyu, Xiaoligou and other skarn-type Fe-Cu deposits and the He’ergou hydrothermal-type Pb-Zn-Ag deposit jointly constitute a three-in-one polymetallic orefield, with the characteristics of typical metallogenic series.     

冀西北水晶屯金矿地质特征及成矿作用研究

水晶屯金矿位于我国重要的金矿集中区——河北省张宣（张家口-宣化）幔枝构造区南部,是张宣地区比较有代表性的中型金矿,张宣幔枝构造演化过程中形成的一系列多期次、多阶段的褶皱和断裂构造体系对该矿的形成和演化起着重要的控制作用。该文以幔枝构造理论为指导,在总结前人资料基础上,通过野外调查,室内综合分析,认为其外围及深部仍具有较大找矿潜力。     

Constraints on rigid zones and other distinct layers at the top of the outer core using CMB underside reflected PKKP waves

Clear PKKP, a P wave reflects off the core-mantle boundary on the core side, is recorded by the transcontinental USArray from two deep earthquakes occurred in South America and Tonga, and one intermediate-depth earthquake in the Hindu Kush region. We compare the PKKP waveforms with the direct P waves to investigate the fine structures near the core-mantle boundary, with a primary focus on the core side. We find no evidence for the existence of a sedimentary layer of lighter elements with a thickness above a few hundreds of meters beneath the reflection points of the two deep events, which are located at the Ninety-East Ridge and South Africa. On the other hand the PKKP wave duration of the Hindu Kush event is almost twice as long as that of the P wave, suggesting that multiple reflections may be occurring at the core-mantle boundary located beneath the Antarctic, which is located inside the so-called tangent cylinder of the outer core. The tangent cylinder is an imaginary cylindrical region suggested by geodynamics studies, which has different flow pattern and may have a higher concentration in lighter elements as compared to the rest of the outer core. One possible explanation of the elongated PKKP is a thin distinct layer with a thickness of a few kilometers at the top of the outer core, suggesting that precipitation of lighter elements may occur at the core-mantle boundary. Our data also indicate an extremely low Q_P of 312, approximately 40% of the PREM average (~780), within the large-scale low-velocity anomaly in the lowermost mantle beneath Pacific.     

沙尘影响下海雾过程气溶胶和雾水组分特征

对2010年3月广东湛江东海岛海雾外场观测试验中获得的雾水样本和气溶胶资料进行分析,研究了海雾中气溶胶和雾水组分的特性以及沙尘过程对其演变的影响。结果表明：东海岛的气溶胶数浓度比内陆城市低1个数量级,环境相对清洁,其早晚的峰值明显,午后存在一个低值。气溶胶谱呈单峰分布,峰值半径为0.02~0.1 μm。雾日的气溶胶数浓度明显低于非雾日,最大值分别集中在0.05~0.1 μm和0.1~0.5 μm。雾过程开始后气溶胶数密度下降,尤其是小粒子端数密度减少显著;雾过程结束后气溶胶数密度会恢复到正常数值。受沙尘影响的过程中雾水中Ca²⁺和Mg²⁺明显增加,气溶胶粒子谱拓宽,直径大于1μm的气溶胶数密度高于其他雾过程;沙尘过境后气溶胶谱变窄,数密度显著减少,离子浓度较低。     

基于GF-1遥感影像的艾比湖区域田间尺度土壤盐渍化监测方法

土壤盐渍化是制约农业生产和发展的主要障碍。目前土壤盐渍化的遥感监测主要基于中、低分辨率卫星影像,并采用传统的基于像元分类方法,对盐渍化信息的细节描述不足,监测精度不高。本文使用国产GF-1影像,结合自上而下的多尺度分割技术和面向对象的信息提取技术,针对田间尺度下的盐渍化信息进行精确地提取、分类,并与传统分类方法进行了对比。结果表明：面向对象法和最大似然法的分类总体精度分别为92.72%和84.31%,Kappa系数分别为0.90和0.78。该技术能准确提取田间尺度下的盐渍地信息,在未来的农田盐渍化高精度监测研究中具有一定应用价值和发展潜力。     

塔里木盆地北缘奥陶系古溶洞和古岩溶沉积中包壳砾石和包壳砾岩的发现及特征*

塔里木盆地北缘奥陶系发育典型的古岩溶,笔者在其中发现了一种非常特殊的沉积物或沉积构造:包壳砾石和包壳砾岩,且这种包壳砾岩之前从未见报道。该包壳砾石和包壳砾岩的结构类似鲕粒或核形石,可分为核心和包壳2部分,大部分呈近圆形或扁圆形,少数形态不规则,直径为数厘米到数十厘米。核心可分为4种,分别是:(1)与溶洞围岩相同的灰岩砾石;(2)由砂岩形成的核心;(3)由砾岩构成的复合核心;(4)由古钙华碎块形成的核心。包壳也可分为4种类型,分别是:(1)具有圈层的包壳;(2)颗粒状包壳;(3)均质包壳;(4)由颗粒状包壳和圈层状包壳组合形成的复合包壳。包壳砾石和包壳砾岩是溶洞和岩溶沉积中的典型产物,其不仅可以作为识别溶洞和岩溶的标志之一,而且具有一定的储集能力,是一种有效的油气储集体。