Laser Ablation ICP-MS Developments and Trends for 2003

This annual review of laser-ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) covers the year 2003. Significant advances were made in understanding laser-sample interactions. In particular, research defined the distribution of particle sizes produced by the interplay of laser wavelength, laser pulse width and the gas environment of ablation. A link between particle sizes and elemental and isotopic fractionation at both the ablation site and in the ICP was established. Experimental 15 7 nm and femtosecond laser systems were tested with promising results. The number of applications of LA-ICP-MS in geology and environmental Earth science continued to grow with particular interest in element concentration and isotope ratio profiling of materials, linking composition to time scales. In situ isotopic ratio measurements were increasingly made using multicollector magnetic sector ICP-MS instruments. Other applications of wide interest included bulk sampling of rocks and ores prepared as lithium borate glasses; low level analysis of platinum-group elements, rhenium and gold in sulfides, metal and silicates; in situ uranium-lead zircon geochronology; and melt and fluid inclusion analysis.     

The development of subgrain misorientations with strain in dry synthetic NaCl measured using EBSD

The development of subgrain boundary misorientations with strain in dry, synthetic NaCl polycrystals, deformed at elevated temperature, has been investigated using electron backscattered diffraction (EBSD). At low natural strains, up to 0.5, average misorientations of subgrain boundaries increase with strain and a power law relationship exists between strain and average misorientations. The average misorientations are strongly influenced by grain orientation, suggesting that the misorientation–strain relationship may also be texture dependent in materials with high plastic anisotropy, like NaCl. A slight grain size dependency of the average misorientations was observed. The results indicate that with suitable calibration, average subgrain boundary misorientations may offer a method for estimating the strain accommodated by dislocation creep in NaCl and thus perhaps in other geological materials, although current theories for polycrystalline plasticity imply that misorientations may also depend on stress in some situations.     

Discussion on influence of cavern’s span on surrounding rock classification

The influence of cavern’s span on surrounding rock classification is getting more and more recognition along with large span underground working’s increasingly coming forth. The authors analyse the timbering expense of cavern in jointed rock mass, the radius of plastic loosened zone and the size effect of macroscopical mechanical parameters of rock mass. Based on the complexion of depressing of surrounding rock’s stability due to increment of cavern’s span, the authors pinpoint attaching importance to the influence of cavern’s span on surrounding rock classification; and suggest reckoning the factor of cavern’s span in surrounding rock classification scientifically by studying the size effect of rock mass’s physico-mechanical parameters.     

Characterization of hydrogeologic properties for a multi-layered alluvial aquifer using hydraulic and tracer tests and electrical resistivity survey

A multi-layered aquifer, typical of riverbank alluvial deposits in Korea, was studied to determine the hydrologic properties. The geologic logging showed that the subsurface of the study site was comprised of four distinctive hydrogeologic units: silt, sand, highly weathered and fresh bedrock layers. The electrical resistivity survey supplied information on lateral extension of hydrogeologic strata only partially identified by a limited number of the geologic loggings. The laboratory column tracer test for the recovered core of the sand layer resulted in a hydraulic conductivity of 5.00×10⁻² cm/s. The slug tests performed in the weathered rock layer yielded hydraulic conductivities of 4.32–7.72×10⁻⁴ cm/s. Hydraulic conductivities for the sand layer calculated from the breakthrough curves of bromide ranged between 2.08×10⁻³ and 2.44×10⁻² cm/s with a geometric mean of 6.89×10⁻³ cm/s, which is 7 times smaller than that from the laboratory column experiment. The trend of increasing hydraulic conductivity with an increase in tracer travel length is likely a result of the increased likelihood of encountering a high conductivity zone as more of the aquifer is tested. The combined hydrogeologic site characterization using hydraulic tests, tracer tests, and column test with geologic loggings and geophysical survey greatly enhanced the understanding of the hydrologic properties of the multi-layered alluvial aquifer.     

兰州市2001年沙尘气溶胶质量浓度的特征分析

 分析了2001年沙尘暴期间兰州与靠近沙尘源区的武威的沙尘浓度和粒径分布特征,并运用对数正态分布规律拟合了沙尘粒径的分布。通过对比武威、皋兰和兰州沙尘暴期间沙尘浓度的变化以及武威与兰州的沙尘粒径分布特征,揭示了河西走廊沙漠对兰州市沙尘暴的影响。     

From soil aggregates to riverine flocs: a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics

Particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity. Their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles. To‐date, hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix. However, lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column. In order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment, soil particle behaviour was tested under controlled laboratory conditions. Seven flume erosion and deposition experiments, designed to simulate a natural erosive event, and five shear cell experiments were performed using three contrasting materials: two of them were poorly developed and as such can not be considered as soils, whilst the third one was a calcareous brown soil. These experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport. Large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence. Indeed, at the maximum applied bed shear stress, the aggregated particles median diameter was found to be three times larger for the well‐developed soil than for the two others. Differences were smaller in the falling limb, suggesting that soil aggregates underwent structural changes. However, characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs, but rather into hybrid soil aggregate–floc particles. Copyright © 2013 John Wiley & Sons, Ltd.     

Size and spatial distribution of loess slides on the Chinese Loess Plateau

ABSTRACT

The size and spatial distribution of loess slides are important for estimating the yield of eroded materials and determining the landslide risk. While previous studies have investigated landslide size distributions, the spatial distribution pattern of landslides at different spatial scales is poorly understood. The results indicate that the loess slide distribution exhibits a power-law scaling across a range of the size distribution. The mean landslide size and size distribution in the different geomorphic types are different. The double Pareto and inverse gamma functions can coincide well with the empirical probability distribution of the loess slide areas and can quantitatively reveal the rollover location, maximum probability, and scaling exponents. The frequency of loess slides increases with mean monthly precipitation. Moreover, point distance analysis showed that > 80% of landslides are located < 3 km from other loess slides. We found that the loess slides at the two study sites (Zhidan and Luochuan County) in northern Shaanxi Province, China show a significant clustered distribution. Furthermore, analysis results of the correlated fractal dimension show that the landslides exhibit a dispersed distribution at smaller spatial scales and a clustered distribution at larger spatial scales.     

Borehole failure analysis in a sandstone under anisotropic stresses

Borehole failure under anisotropic stresses in a sandstone is analyze numerically for various borehole sizes using a nonlinear elastic–plastic constitutive model for a Cosserat continuum. Borehole failure is identified as macroscopic failure of the borehole through the development of shear bands and breakouts. The results compare well both qualitatively and quantitatively with experimental results from polyaxial tests on Red Wildmoor sandstone. They show that the hole size effect of the borehole failure strength is independent of the far‐field stress anisotropy and follows a ? power law of the hole size. A similar scale effect equation with a ? power law is proposed for the scale effect of the maximum plastic shear strain at failure. This equation can be useful for better predicting hole‐size‐dependent failure with standard codes based on classical continua. The effect of stress anisotropy on the borehole failure stress is found to be independent of the hole size. The failure stress decreases linearly to 40% as the stress anisotropy increases. However, the maximum plastic shear strain at failure is stress anisotropy independent and therefore the critical plastic shear strain for failure is only hole‐size dependent. Copyright © 2009 John Wiley & Sons, Ltd.