Optimization of the Sampling Technique for the Determination of Dissolved Hydrogen in Groundwater

In this study a field‐sampling technique for dissolved hydrogen (H₂) in groundwater will be presented which allows the transport of gaseous samples into the laboratory for further analysis. The method consists of transferring the headspace trapped in a gas‐sampling bulb which is continuously purged by groundwater into previously evacuated vials using a gas‐tight syringe. Three transfer steps with preceding evacuation of the vial led to a H₂‐recovery of 100 % in laboratory experiments. The method has been applied to determine H₂ concentrations in an aquifer contaminated with chlorinated solvents. Tests concerning the effect of different pumping techniques on H₂ concentrations revealed that most reliable values were obtained with a bladder pump, while an electrically driven submersible pump generated considerable amounts of hydrogen due to electrochemical interactions with the sampled water. Concentrations of dissolved hydrogen in field and laboratory samples were about two orders of magnitude higher when sampling was performed with the electrically driven submersible pump compared to sampling with the bladder pump and a peristaltic pump. Lab experiments with a Plexiglas reservoir to produce H₂‐enriched water were used to study the effect of two tubing materials (PVC, polyamide) on H₂ losses. PVC tubing turned out to allow transfer of H₂‐enriched water over 25 m without significant losses, while PA‐tubing was not suitable for sampling of H₂.     

用激光测距资料解地球定向参数的模型改进

详细介绍了与SLR观测资料的高精度相适应的解EOP模型的改进，并且在复弧法中使用这个改进模型。当轨道参数为全局量，EOP参数为子弧量时，其中解极移运动Xp，Yp和日长变化率DUTIR的模型的更新，提高了解EOP的精度，特别提高了解DUTIR的精度；同时也提高了整个弧段的定轨精度。在EOP的改进模型中，以周日和半周日为周期的分量虽然对提高EOP本身的精度没有什么帮助，但是对整个弧段定轨精度的提高还是有益的。本文用1995—1999年LAGEOS-1的资料解得的EOP序列精度：Xp达0．43mas，Yp达0．41mas，DUTIR达0．022ms。90天弧长定轨残差好于2cm。     

西南岩溶石山地区石漠化信息自动提取技术研究

介绍了以TM数据为信息源,基于GIS系统平台的矢量化石漠化信息计算机自动提取原理、方法、步骤及提取效果。     

Digital model of corrected accumulated flow for peak discharge data acquisition and drainage system design

The design of a drainage system for a roofing slate quarry was implemented by the enhancement of discharge peak estimation, and the uncertainty inevitably associated with the engineering model was reduced.

The development of a topographical, geological, and vegetation cover database developed from a Geographical Information System (GIS) allowed for the definition of the drainage network for a hydraulic system, along with the calculation of the runoff coefficient. This is applied to the digital model of accumulated flow (DMF) as a weight correction coefficient, using a matrix-based model at 5×5 m resolution. The new digital model of corrected accumulated flow (DMCF) is the result of combining the thematic maps with the map of slope <3%, which was previously created from the slope model. It is demonstrated that this new model allows to apply the “Rational Method” on cartographic units defined by the GIS.

The DMCF is compared with other traditional applications of the Rational Method based on the calculation of the discharge peak considering: (1) the drainage basin as a single watershed or (2) defining an average runoff coefficient in each sub-watershed. Both approaches have bigger discharge peaks than those obtained by the DMCF since the slope, lithology, and vegetation cover have average values, and the runoff coefficient is poorly defined, increasing the uncertainty in the discharge peak.     

Land subsidence caused by groundwater exploitation in Suzhou City,China

Suzhou City, located at the lower reaches of the Yangtze River in southeastern Jiangsu Province, is one of the few cities in China which suffer from severe ground settlement. A research project was carried out to investigate this problem. Geological and hydrogeological studies show that there is a multi-layered aquifer system with three distinct, soft mud layers of marine and lagoonal origins. An examination of historical records of groundwater extraction, water levels, and ground settlement shows that the ground subsidence is associated with the continuously increasing groundwater extraction in the deep, confined aquifer. It is believed that the consolidation of the soft mud layers, especially the third layer which is thick and close to the main pumped aquifer, contributes to the ground settlement. A three-dimensional finite difference numerical model representing the multi-layered aquifer system was developed to study the ground settlement in response to groundwater extraction. By calibrating the model with both the measured groundwater level and ground settlement, the aquifer parameters were estimated. The model outputs fit reasonably well with the observed results, which indicates that the numerical model can reproduce the dynamic processes of both groundwater flow and soil consolidation. The hydraulic conductivity of the third mud layer near the center of the ground settlement has been reduced by over 30% in the last 14 years. The gradual deterioration in the hydraulic conductivity of the mud may have significant adverse effect on the sustainable groundwater resource of the deep confined aquifer, since the recharge from the shallow aquifers through the mud layer is the only source of water to the deep aquifer. An analysis of the spatial distributions of groundwater drawdown and ground settlement shows that the area with maximum drawdown is not necessarily the area with maximum ground settlement due to the occurrence of the soft mud layer. A simple reallocation in pumping rates on the basis of the spatial distribution of the thick mud layer could significantly reduce the ground settlement. Electronic Publication     

Surface analysis of pyrite in the No. 9 coal seam, Wuda Coalfield, Inner Mongolia, China, using high-resolution time-of-flight secondary ion mass-spectrometry

The chemical composition of pyrite in coal can be used to investigate its geological and mineralogical origin. In this paper, high-resolution time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to study the chemical composition of various pyrite forms in the No. 9 coal seam (S_t,d=3.46%) from the Wuda Coalfield, Inner Mongolia, northern China. These include bacteriogenic, framboidal, massive, cell-filling, fracture-filling, and nodular pyrites. In addition to Fe⁺ (⁵⁴Fe⁺, ⁵⁶Fe⁺, ⁵⁷Fe⁺), other fragment ions were detected in bacteriogenic pyrites, such as ²⁷Al⁺, Si⁺ (²⁸Si⁺, ²⁹Si⁺, ³⁰Si⁺), ⁴⁰Ca⁺, Cu⁺ (⁶³Cu⁺, ⁶⁵Cu⁺), Zn⁺ (⁶⁴Zn⁺, ⁶⁶Zn⁺, ⁶⁷Zn⁺, ⁶⁸Zn⁺), Ni⁺ (⁵⁸Ni⁺, ⁶⁰Ni⁺, ⁶²Ni⁺), and C₃H₇⁺. TOF-SIMS images show bacteriogenic pyrites are relatively rich in Cu, Zn, and Ni, suggesting that bacteria probably play an important role in the enrichment of Cu, Zn, and Ni during their formation. Intense positive secondary ion fragments from framboidal aggregates, such as ²⁷Al⁺, ²⁸Si⁺, ²⁹Si⁺, AlO⁺, CH₂⁺, C₃H₃⁺, C₃H₅⁺, and C₄H₇⁺, indicate that formation of the framboidal aggregates may have occurred together with clay mineral and organic matter, which probably serve as the binding substance. The intense ions of ²⁸Si⁺ and ²⁷Al⁺ from massive pyrites also suggest that their pores incorporated clay minerals during crystallization. Together with the lowest ²⁸Si⁺/²³Na⁺ value, the intense organic positive secondary ion peaks from cell-filling pyrites, such as C₃H₃⁺, C₃H₅⁺, C₃H₇⁺, and C₄H₇⁺, indicate that pyrite formation may have accompanied dissolution or disintegration of the cell. The intense P⁺ peak was observed only in the fracture-filling pyrite and the highest ²⁸Si⁺/²³Na⁺ value of fracture-filling pyrite reflects its epigenetic origin. Together with XRD and REEs data, the stronger ⁴⁰Ca⁺ in nodular pyrite than other pyrite forms shows seawater influence during its formation.     

上地幔变黏度小尺度对流的数值研究

基于二维模型，利用有限元方法，研究上地幔-岩石圈系统的变黏度小尺度对流. 考虑该系统的黏度随温度以指数形式变化，数值结果表明，当黏度随温度变化较剧烈时，由于低温高黏度，系统的最上部物质不参与对流，系统发育形成一个类似于岩石圈的静止盖层. 计算表面热流、地形起伏及重力异常与对流格局有较好的相关性，高热流、上升地形对应于对流的上升区，反之低热流、下降地形与对流的下降区对应.     

中心回线瞬变电磁法2.5维有限单元算法

瞬变电磁法的野外资料解释基本上停留在一维水平，本文从生产实践中常用的中心回线法入手，基于电磁场本身的叠加原理，从麦克斯韦方程组出发，导出了中心回线瞬变电磁2.5维二次场（纯异常）的有限单元计算公式. 该算法采用三角形有限元网格，在尽可能拟合地下电性断面的情况下减少有限元网格的节点数和单元数；用选主元的LU分解法求解线性方程组，做到了在移动场源时只需改变右端项；在反傅氏变换中，使用新的波数选取方案，让波数m随时间t滑动. 最后给出的算例表明，该算法直接计算异常场，计算速度快、精度高.     

井间电阻率层析成象的某些进展

用有限元法作电阻率层析成象的核心问题是Ｊａｃｏｂｉ矩阵的求取和反演成象算法的研究。本文主要论述了这两方面的最新进展，即求取Ｊａｃｏｂｉ矩阵的格林函数法，用于反演成象计算的平滑度约束反演。文中通过理论模型的成象计算，比较了两种反演算法的成象效果。     

高粘性牛顿流体粘性耗散的快速计算方法

螺旋泵可用来输送高粘性液体，该过程中由于液体的温度升高而粘度降低，因而其粘性耗散不能忽略。本文介绍一种上述情况下计算液体粘度、泵的功率和压力降的近似公式。