双轴压缩条件下颗粒材料中力链的演化

针对无黏性颗粒材料,开展了柔性边界双轴压缩数值试验,分析了不同围压下力链的数量、方向概率等随轴向应变的变化。研究结果表明：不断加载使得游离的高应力颗粒有所减少,荷载更多的被力链承担;统计意义上,力链最大长度为9个颗粒。轴向±30o范围内力链概率随应变的发展与偏应力一致,而与其邻接的[40o,60o]和[120o,140o]两个方向上的力链概率随应变的发展与偏应力相反;双轴试样剪切破坏时有单剪切带和双剪切带两种模式,当[40o,60o]和[120o,140o]两个角度区间的力链概率有较大差异时,剪切带出现在力链较少的角度区间;当这两个角度区间力链概率接近时,试样中将出现两个剪切带。     

三维交叉裂隙渗流传质特性数值模拟

对交叉裂隙渗流传质特性的定量描述是研究整个裂隙网络渗透传质特性的基础。为真实模拟水流及溶质在三维交叉裂隙中的运移过程,首先通过三维轮廓仪获取天然岩石裂隙表面的形貌数据,再应用三维重构技术生成相应的三维交叉裂隙模型,随后求解Navier-Stokes方程,假定溶质运移满足Fick定律,模拟水流和溶质在三维交叉裂隙中的运移过程。通过对比粗糙裂隙模型与平行平板模型的模拟结果发现：粗糙度对流体的分布及流动状态存在显著的影响;不同进、出口工况下的流体流动及溶质运移状态亦表明：裂隙交叉的几何形貌会显著地影响溶质混合行为。这些结果表明,目前被广泛采用的平行平板模型在评估岩体内特别是交叉口的物质运移特性时将导致较大的偏差,在将来的研究中有必要针对裂隙交叉口的几何特征建立修正的模型以提高评估的准确性。     

Sources of pollution and distribution of Pb,Cd and Hg in Wrocław soils: Insight from chemical and Pb isotope composition

Human activities in cities affect properties of urban soils. In particular, urban soils often contain high contents of harmful metals even in deeper horizons added to them from diverse sources over centuries of the city development. This is reflected in complex distribution of metals in bulk soils with depth and the complex metal fractionation, but the exact sources of the metals are difficult to identify. This is also the situation in soils from Wroclaw, one of the largest cities in Poland. Potentially harmful elements Pb, Cd and Hg were examined in six profiles located along the major communication route and compared to two non-urban soils profiles located close to the same route. In all of the urban profiles, Pb and Cd exceeded the element contents observed in non-urban profiles and showed an erratic distribution compared to the more predictable one in non-urban soils. The differences between urban and non-urban profiles were explained as the result of contamination coming from more pollution sources in the case of urban soils, the conclusion supported by Pb isotope analyses. In fact, Pb isotopes showed that the contamination sources in urban soils included leaded petrol, coal combustion, smelting and possibly old pre-industrial ore processing, whereas leaded petrol and pre-industrial lead were the only possible anthropogenic sources in non-urban soils. The comparison of Wrocöaw soils with those from cities of comparable size Kraków and Poznań show similar ranges of metal contents with implication that urban pollution oversteps diverse geogenic chemical background. On the other hand, the comparison with other European cities show large variability in metal contents and suggest that urban soils contamination is time integrated and reflects long-term industrial evolution of each country.     

Bed sediment entrainment by streamflow: State of the science

In fluvial sedimentology, bed sediment entrainment by streamflow has a decisive role in controlling several fluvial processes. Owing to its huge practical importance, the subject has been painstakingly explored for over a century. However, a detailed understanding of the mechanism of the bed sediment entrainment phenomenon achieved hitherto is far from complete. The central theme of bed sediment entrainment is occupied by the sediment entrainment threshold, which varies enormously in its qualitative definition, identification and quantification encompassing a broad range of spatiotemporal scales. This article presents the state of the science of the entrainment of non‐cohesive bed sediments under a steady‐unidirectional streamflow. It begins with the diverse definitions and representations of the entrainment threshold criterion from both qualitative and quantitative perspectives, scrutinising its suitability and ambit of applicability. Then, the effects of energetic factors that drive the entrainment threshold criterion are critically appraised. The indispensable mechanisms of bed sediment entrainment, including the theoretical background and modelling strategies, the role of turbulent bursting phenomenon and the phenomenological perspective into the origin of the scaling laws of sediment entrainment, are explained. Throughout the article, special emphasis is given to the strengths and weaknesses of the current state of the science. In addition, a deliberate attempt is made to invoke the thought‐provoking ideas on the multifarious features of bed sediment entrainment. Finally, the innovative perspectives on the bed sediment entrainment are provided and the concluding remarks are made, elucidating the major challenges and suggesting the prospective ways to resolve them as a future scope of research.     

Review of the Tropical Gyre in the Indian Ocean with Its Impact on Heat and Salt Transport and Regional Climate Modes

Due to the IO monsoon impact, the tropical IO circulation has significant seasonal variation, especially in the northern IO. However, in mean-state, a relatively closed current loop is established by eastward current along the equator and westward current south of equator, which is regarded as Tropical Gyre in the Indian Ocean. Based on this circulation system, relevant studies were reviewed. Its impact on heat and salt transports and regional climate changes were discussed.     

云南保山金厂河铁铜铅锌多金属矿床S-Pb同位素特征

滇西金厂河铁铜铅锌多金属矿床位于云南省保山地块北部、NS向保山—施甸复背斜与NNW向澜沧江断裂的锐角交汇部位的南部。文章在以往工作的基础上,研究金厂河铁铜铅锌多金属矿床的S-Pb同位素特征,这对分析该矿床成矿物质来源及探究成矿过程具有十分重要的意义。采样及测试结果显示,该矿床硫化物的δ³⁴S值为+2.5‰~+11.1‰,平均+5.65‰,说明矿床硫化物硫的来源为深部幔源岩浆硫和混合硫（复杂硫）;共生含硫矿物中富集δ³⁴S的均值为：黄铜矿（+5.65‰） > 闪锌矿（+5.38‰） > 方铅矿（+3.45‰）,表明矿床硫同位素分馏未达到平衡。²⁰⁷Pb/²⁰⁴Pb—²⁰⁶Pb/²⁰⁴Pb、²⁰⁸Pb/²⁰⁴Pb—²⁰⁶Pb/²⁰⁴Pb铅同位素模式图中样品点分布位置及朱炳泉Δβ—Δγ变化范围图解结果表明,该矿床铅同位素主要来源于上地壳,此外和深部岩浆的侵入活动相关。     

贵州上二叠统龙潭组煤系地层地球化学特征及物源分析:来自黔普地1井的证据

为厘清贵州上二叠统龙潭组煤系地层的物源,以黔西南地区黔普地1井为研究对象,采集了上二叠统龙潭组的岩心进行稀土元素分析。结果表明,龙潭组的稀土总量较高(177.03×10^-6～592.58×10^-6),轻、重稀土分馏明显,稀土元素配分模式呈轻稀土富集、重稀土相对亏损的右倾型;(La/Sm)_N为2.63～4.72,(Gd/Yb)_N值为1.47～2.218,表明轻稀土分馏较重稀土严重;δEu无异常。研究表明,其形成的构造环境与大陆边缘与大陆弧相近,推测黔普地1井二叠系龙潭组物质来源以玄武岩为主。     

‘Box‐Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry

Although electron probe microanalysis and secondary ion mass spectrometry are widely used analytical techniques for geochemical and mineralogical applications, metrologically rigorous quantification remains a major challenge for these methods. Secondary ion mass spectrometry (SIMS) in particular is a matrix‐sensitive method, and the use of matrix‐matched reference materials (RMs) is essential to avoid significant analytical bias. A major problem is that the number of available RMs for SIMS is extremely small compared with the needs of analysts. One approach for the production of matrix‐specific RMs is the use of high‐energy ion implantation that introduces a known amount of a selected isotope into a material. We chose the more elaborate way of implanting a so‐called ‘box‐profile’ to generate a quasi‐homogeneous concentration of the implanted isotope in three dimensions, which allows RMs not only to be used for ion beam analysis but also makes them suitable for EPMA. For proof of concept, we used the thoroughly studied mineralogically and chemically ‘simple’ SiO₂ system. We implanted either ⁴⁷Ti or ⁴⁸Ti into synthetic, ultra‐high‐purity silica glass. Several ‘box‐profiles’ with mass fractions between 10 and 1000 μg g^?1 Ti and maximum depths of homogeneous Ti distribution between 200 nm and 3 μm were produced at the Institute of Ion Beam Physics and Materials Research of Helmholtz‐Zentrum Dresden‐Rossendorf. Multiple implantation steps using varying ion energies and ion doses were simulated with Stopping and Range of Ions in Matter (SRIM) software, optimising for the target concentrations, implantation depths and technical limits of the implanter. We characterised several implant test samples having different concentrations and maximum implantation depths by means of SIMS and other analytical techniques. The results show that the implant samples are suitable for use as reference materials for SIMS measurements. The multi‐energy ion implantation technique also appears to be a promising procedure for the production of EPMA‐suitable reference materials.     

火山—热液作用相关细粒沉积岩研究现状及前沿探索

陆相细粒沉积岩是中国含油气盆地中重要的烃源岩和致密油储集层。随着对烃源岩、致密油、页岩油-气勘探开发研究的不断深入,陆相细粒沉积岩取得了一系列重要进展并持续进行着前沿探索。作者论述了传统细粒沉积岩基本概念及演变,岩石、矿物组成特征、成因机制与分类方法。结合近年来在陆内裂谷盆地陆相细粒沉积岩中广泛分布的火山—热液物质的新报道及研究成果,认为火山物质、热液喷流物质不仅参与了陆相黑色细粒岩系的沉积和成岩作用,也与油气生成有密切关系。加强对陆相细粒沉积研究,探讨深源碎屑及热液流体的来源及其对细粒沉积过程的影响,既有利于丰富、完善沉积学和陆相含油气盆地生油理论,也有利于更好地指导致密油、页岩油-气的勘探开发。     

Nematode distribution in cultivated and undisturbed soils of Guinea Savannah and Semi-deciduous Forest zones of Ghana

Climate change affects air temperature, sea levels as well as the soil and its ecosystem. The Guinea Savannah and Semi-deciduous Forest zones of Ghana are characterized by different climatic conditions and vegetative cover. Annual average temperature has been steadily increasing whilst annual total rainfall has been decreasing in both zones, and this has been causing a southward shift of the Savannah into the Forest zone. Soil organisms provide crucial ecosystem services which are required for sustainable agriculture and food production yet crop cultivation disturbs the soil ecosystem. The harsh conditions associated with the Savannah further expose the soil ecosystem to disturbance and loss of biodiversity which threatens food production and security. Soil nematodes are the most abundant animals in the soil and play a central and critical role in the soil food web complex. Studying the nematode community structure gives a reflection of the status of the entire soil ecosystem. Soil samples were taken from cultivated and natural landscapes in the Guinea Savannah and Semi-deciduous Forest agroecological zones to analyse the nematode community. Results from the study showed the Guinea Savannah zone recording warmer soil temperatures, lower organic matter percentage and lower nematode diversity(Genus Richness) as compared to the Semi-deciduous Forest zone. If the Savannah continues to shift southward, the Forest zone soil ecosystem risks disturbance and loss of biodiversity due to the harsh Savannah conditions. Our findings indicate that prevailing crop cultivation practices also disturb soil ecosystem in the two ecological zones which span across West Africa. A disturbed soil ecosystem endangers the future of food production and food security.