Evaluation of Subsurface Lithologic Units for Groundwater Exploration in the Barind Tract of Bangladesh

Barind Tract, located north western part of Bangladesh, is one of the most diversified physiographic units of the country. The surface water supply in this part is particularly limited, so the irrigation is almost entirely depends on groundwater. However, over exploitation indicates falling groundwater heads in this area. The objective of present study is to examine the nature of the aquifer system Barind Tract of Bangladesh in order to assess the sustainability of groundwater yield. Borehole lithology data were collected, processed and analyzed for this purpose. Representative panel diagram, 3-D stratigraphic and cross-sectional views were also prepared for necessary assessment of the variation of individual subsurface stratum in different locations. The study identified three subsurface geologic formations namely, a top clay layer, sand layer of different grain size and at the bottom an impermeable clay zone. Maps of formation thickness and index revealed that aquifer thickness is low in the north-western corner and in some places of middle of south-western corner. The thickness of sand formation in other places is recorded above 20 m. It is expect that the finding of the study will help groundwater resources development, planning and management in the area.     

Heavy metal contamination of cultivated wetland soils along a typical plateau lake from southwest China

Topsoil (0–20 cm) samples were collected from four cultivated wetlands including Northern and Western Fields (about 30-year tillage), and Southern and Western Fields (about 20-year tillage) along the Yilong Lake of China in October, 2005. Total concentrations of As, Cr, Cu, Pb, and Zn were determined using the inductively coupled plasma atomic absorption spectrometry in order to assess contamination status in four sampling plots. Results showed that the average concentrations of these heavy metals in Northern and Western Fields were significantly (P < 0.01) higher than those in reference soils, while they were generally lower in Southern and Eastern Fields. All the mean concentrations of heavy metals were lower, except that the average concentrations of As and Cr in Northern Field slightly exceeded the soil quality guidelines. The contamination indices showed low-contamination levels for As, Cu, Pb, and Zn in Northern and Western Fields, while no contamination levels could be observed in Southern and Eastern Fields. As for Cr, they showed moderate-contamination levels in Northern Field, but low or no contamination levels in other three Fields. The integrated contamination index values indicated Northern and Western Fields were moderately contaminated, while Southern and Eastern Fields were less contaminated. The same contamination sources of these heavy metals were identified in these fields using factor- and cluster analysis.     

西宁市区土层剪切波速随深度变化特征

通过对西宁市区67个钻孔剪切波速资料整理,采用最小二乘法进行统计回归分析,得到西宁市土层剪切波速Vs随土层埋深H的经验关系式,西宁市典型土类Vs与H的经验关系。并且通过实测剪切波速与预测剪切波速的对比,验证所得经验关系式的适用性。     

罗源湾水母类的生态研究

样品于1986年11月至1987年10月在福建省罗源湾10个站位采集。经鉴定有52种水母。它们可分为沿岸暖水、沿岸暖温和大洋广布三种生态类群。水母类总数量和种类数的季节分布呈单周期,两者高峰均出现在7月。低谷分别出现于11月和1月。在平面分布上,以拟细浅室水母Lensia subtiloides占优势的月份,数量从湾口向湾顶递减,而以球型侧腕水母Pleurobrachia globosa占优势的月份,数量却递增。文中还讨论了水母类的分布和环境因素的关系。     

The polar form of the spherical harmonic spectrum: implications for filtering <Emphasis Type="BoldSmallCaps">grace</Emphasis> data

Representing the spherical harmonic spectrum of a field on the sphere in terms of its amplitude and phase is termed as its polar form. In this study, we look at how the amplitude and phase are affected by linear low-pass filtering. The impact of filtering on amplitude is well understood, but that on phase has not been studied previously. Here, we demonstrate that a certain class of filters only affect the amplitude of the spherical harmonic spectrum and not the phase, but the others affect both the amplitude and phase. Further, we also demonstrate that the filtered phase helps in ascertaining the efficacy of decorrelation filters used in the grace community.     

Effect of heat treatment on dynamic properties of selected rock types taken from the Salt Range in Pakistan

Temperature is one of the variables that influence the elasto-plastic behavior and integrity of rock outcrops. Fluctuations in temperature can trigger alteration of some of the mineral properties and impact the brittle-plastic transition. Initiation and propagation of thermally induced tension cracks tend to weaken most rock types. The principal goal of this study was to anticipate impacts of thermal stress-strain cycles on the dynamic response of representative rock units exposed in the Khewra Gorge of the Salt Range Punjab of Pakistan. Ten types of sedimentary rock units were sampled, including marl, dolomite, three types of limestone, and five different sandstones exhibiting varying characteristics in outcrop. Boulder specimens were collected from the field and transported to the laboratory to prepare 50 drill cores that could be subjected to thermal cycling between 50 and 200 °C in increments of 50 °C. Room temperature core samples were tested using an Erudite resonance frequency meter to measure their Q-factors and the resonance frequency (F_r) at an applied loading frequency of 7 KHz with 0.01 V output voltage. Results suggest that thermal cycling tends to reduce the dynamic Young’s modulus (E_d) and Q-factor. Other parameters, such as damping ratio (ξ), specific damping capacity (Ψ), and loss factor (?) appeared to increase with increasing temperature cycles, likely as a result of developing thermally induced tensile fractures. The resultant values of the null hypothesis (t-critical and t-stats) suggests that the null hypothesis can be discarded because there was no observable difference between the measured and expected values for the cores tested. The observations and data emanating from this study might be useful in designing low-level radioactive waste landfills, nuclear waste repositories, and deep underground excavations where the increased temperature could alter the mechanical behavior of the parent rock mass.     

Assessment of the reliability of supervised classifications of Landsat-7, ASTER,and SPOT-5 multispectral data in rock unit discriminations of Jabal Daf-Wadi Fatima area,Saudi Arabia

Multispectral, multiresolution remotely sensed data were processed to emphasize geological interpretation of Jabal Daf-Wadi Fatima area. The investigated area is situated in the central western part of Saudi Arabia and geologically consists of igneous and metamorphosed rocks overlain by sedimentary sequence belonging to the Arabian-Nubian Shield. Three sets of digital satellite data, Landsat-7 ETM+, ASTER, and SPOT-5, were used in this study. The application of image processing techniques enables to identify and delineate the lithologic units and the structural features of the study area. The results of this study indicate that the confusion matrix of the three maximum likelihood supervised classifications of the three datasets shows that the Landsat ETM+ bands scored the best degree of average and overall accuracy (77 and 78%, respectively). This classification distinguishes most of the rock units for mapping in the investigated area. The supervised classification of ASTER and SPOT bands has lower degrees of accuracy than the classified Landsat data. The supervised classification of SPOT bands has a degree of average and overall accuracy of 66 and 67%, respectively, but it is the best for distinguishing the spectral signatures of the different members of Fatima Formation (lower, middle, and upper members). The statistical analyses of the confusion matrices of classifications and the interpretation of the produced classified thematic maps revealed that the classification accuracy does not necessary depend on the spatial resolution of satellite data. The data of the highest spatial resolution such as SPOT data are also very useful in emphasizing and classifying the rock units of a small outcrop area. The detailed geological map of Jabal Daf-Wadi Fatima area is interpreted in this work from supervised classified images of different resolutions as well as the structure map of this area. This study shows that it is preferable to use the supervised classifications of multiresolution data for rock unit discrimination in detailed field mapping.     

Structural properties of Urfa stone doped with erbium oxide

In this study, we investigated the structural properties of Urfa stone (US) doped with erbium oxide (Er₂O₃). Solid US was powdered by using an agate mortar, and its elemental composition was determined using inductive coupling plasma (ICP) methods. Varying amounts of Er₂O₃ (5, 10, 20, 30, and 40%) were added as a dopant to the US powder using mechanical alloying methods. The resultant samples were sintered at 1000 °C for 1 h. The structural properties of the Er₂O₃-doped US samples were subsequently investigated using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and photoluminescence methods. Results from the XRD analysis of the Er₂O₃-doped US powder indicated two crystalline phases: (1) calcium oxide (CaO) or lime and (2) Er₂O₃. After the samples were sintered at 1000 °C, CaO, Er₂O₃, calcium carbonate (CaCO₃), and mixed crystalline phases were observed. Results from the FTIR analysis of the Er₂O₃-doped US samples indicated absorption bands at 711.91, 872.08, and 1396.87 cm^?1 in the spectra. Finally, photoluminescence analysis results indicated a shift in the emission and excitation bands to longer and shorter wavelengths, respectively, in the solid state (non-aqueous media) US-Er complex.     

Geospatial assessment of soil erosion intensity and sediment yield: a case study of Potohar Region,Pakistan

Estimation of spatial extent of soil erosion, one of the most serious forms of land degradation, is critical because soil erosion has serious implications on soil fertility, water ecosystem, crop productivity and landscape beauty. The primary objective of the current study was to assess and map the soil erosion intensity and sedimentation yield of Potohar region of Pakistan. Potohar is the rainfed region with truncated and complex topography lying at the top of the Indus Basin, the world’s largest irrigation networks of canals and barrages. Spatially explicit Revised Universal Soil Loss Equation (RUSLE) Model integrated with Remote Sensing-GIS techniques was used for detecting/mapping of erosion prone areas and quantification of soil losses. The results show that the Potohar region is highly susceptible to soil erosion with an average annual soil loss of 19 tons ha^?1 year^?1 of which the maximum erosion (70–208 tons ha^?1 year^?1) was near the river channels and hilly areas. The sediment yield due to the erosion is as high as 148 tons ha^?1 year^?1 with an average of 4.3 tons ha^?1 year^?1. It was found that 2.06% of the total area falls under severe soil erosion, 13.34% under high erosion, 15.35% under moderate soil erosion while 69.25% of the area lies in the low (tolerable) soil erosion. Chakwal and Jhelum districts of the region are seriously affected by erosion owing to their topography and soil properties. The information generated in this study is a step forward towards proper planning and implementation of strategies to control the erosion and for protection of natural resources. It is, hence, necessary that suitable water harvesting structures be made to control water to prevent soil erosion and provision of water in the lean season in this region. Tree plantation and other erosion control practices such as strip cropping can also minimize soil erosion in this region.     

Efficacy of laser cleaning in the removal of biological patina on the volcanic scoria of the rock-hewn churches of Lalibela,Ethiopia

The Lalibela rock-hewn churches are one of the most important religious pilgrimage sites in Ethiopia. These churches are carved from the scoriaceous basalt rock substrate, which has been exposed to attack by biological agents with significant loss of surface material. Particularly, the widespread growth of lichens and other microorganisms on the carved surfaces of the churches has proven to represent a substantial threat for the preservation of the site. In this study, laboratory tests have been conducted to assess the feasibility of using laser technology as an efficient cleaning method of biological patina from polymineralic stone substrates. Multi-analytical techniques were applied for the characterization of the stone samples collected from two of the Lalibela churches: Bete Giyorgis and Bete Amanuel. Stone samples artificially inoculated with bacteria, yeast, fungi isolates, and lichen-encrusted samples were laser cleaned using UV and IR laser wavelengths. The high content of Fe and Ti oxides and the high porosity have made the stone surfaces easily susceptible to low-energy laser treatment. Results indicate that laser cleaning can be applied to polymineralic lithotypes and UV irradiation can successfully remove lichen colonies. Further studies need to be conducted to optimize the laser procedure in polymineralic, high porosity stones.