排序方式： 共有26条查询结果，搜索用时 15 毫秒
1.
2.
3.
Ghulam Jeelani Rouf Ahmad Shah Rajendrakumar D. Deshpande Ashok P. Dimri Suraj Mal Anupam Sharma 《水文研究》2021,35(11):e14406
Western disturbances (WDs) and Indian summer monsoon (ISM) led precipitation play a central role in the Himalayan water budget. Estimating their contributions to water resource is although a challenging but essential for hydrologic understanding and effective water resource management. In this study, we used stable water isotope data of precipitation and surface waters to estimate the contribution of ISM and WDs to the water resources in three mountainous river basins - Indus, Bhagirathi and Teesta river basins of western, central and Eastern Himalayas. The study reveals distinct seasonality in isotope characteristics of precipitation and surface waters in each river basin is due to changes in moisture source, hydrometeorology and relief. Despite steady spatial variance in the slope and intercept of regression lines from the Teesta to Indus and the Bhagirathi river basins, the slope and intercept are close to the global meteoric water line and reported local meteoric water line of other regions in the Himalayas and the Tibetan Plateau. The two-component end-member mixing method using d-excess as tracer were used to estimate the contribution from ISM and WD led precipitation to surface water in aforementioned river basins. The results suggest that the influence of the ISM on the water resources is high (>72% to annual river flow) in Teesta river basin (eastern Himalayas), while as the WDs led precipitation is dominantly contributing (>70% average annual river flow) to the surface waters in the Indus river basin (western Himalayas). The contribution of ISM and WD led precipitation in Bhagirathi river basin is 60% and 40%, respectively. The findings demonstrate that the unusual changes in the ISM and WD moisture dynamics have the potential to affect the economy and food security of the region, which is dependent on the availability of water resources. The obtained results are of assistance to policy makers/mangers to make use of the information for better understanding hydrologic response amid unusual behaviour of the dual monsoon system over the region. 相似文献
4.
Suraj Dhungana Charles R. Anthony III Larry E. Hersman 《Geochimica et cosmochimica acta》2007,71(23):5651-5660
Pyridine-2,6-bis(monothiocarboxylate) (pdtc), a metabolic product of microorganisms, including Pseudomonas putida and Pseudomonas stutzeri was investigated for its ability of dissolve Fe(III)(hydr)oxides at pH 7.5. Concentration dependent dissolution of ferrihydrite under anaerobic environment showed saturation of the dissolution rate at the higher concentration of pdtc. The surface controlled ferrihydrite dissolution rate was determined to be 1.2 × 10−6 mol m−2 h−1. Anaerobic dissolution of ferrihydrite by pyridine-2,6-dicarboxylic acid or dipicolinic acid (dpa), a hydrolysis product of pdtc, was investigated to study the mechanism(s) involved in the pdtc facilitated ferrihydrite dissolution. These studies suggest that pdtc dissolved ferrihydrite using a reduction step, where dpa chelates the Fe reduced by a second hydrolysis product, H2S. Dpa facilitated dissolution of ferrihydrite showed very small increase in the Fe dissolution when the concentration of external reductant, ascorbate, was doubled, suggesting the surface dynamics being dominated by the interactions between dpa and ferrihydrite. Greater than stoichiometric amounts of Fe were mobilized during dpa dissolution of ferrihydrite assisted by ascorbate and cysteine. This is attributed to the catalytic dissolution of Fe(III)(hydr)oxides by the in situ generated Fe(II) in the presence of a complex former, dpa. 相似文献
5.
B. S. Badmus O. D. Akinyemi J. A. Olowofela G. M. Folarin 《Journal of the Geological Society of India》2012,80(6):845-854
Geological structures are 3-Dimensional (3D) in nature, thus 1-Dimensional and 2-Dimensional surveys cannot adequately model them. However, sophisticated 3D survey equipment are very expensive. In this study, a singlechannel ABEM SAS 300B Terrameter was used to obtain 3D models of the subsurface. This survey was carried out at three different locations within Abeokuta, a basement complex terrain of southwestern Nigeria. The area falls within longitudes 3.35° and 3.38° East and latitudes 7.22° and 7.46° North respectively, with coordinates of 2550.0 m North and 1724.2 m East. A manual 4-electrode system was used in the Electrical Resistivity Tomography survey at the three locations. Each location was marked into 7 by 7 square grids with 1 m, 3 m and 5 m unit electrode spacings in succession. The pole-pole array was used with the two remote electrodes placed at distances of 23 m, 40 m and 65 m from the grids of 1 m, 3 m and 5 m unit electrode spacings respectively, to reduce their telluric effects on the measured apparent resistivity values. To reduce survey time consumption, the cross-diagonal survey method was adopted. The data obtained were analysed using a 3D inversion software called RES3DINV and 3-Dimensional models of the subsurface were also generated using Slicer Dicer graphics software. The study revealed layers extending to depths of 7.75 m, 23.2 m and 38.7 m for unit electrode spacings of 1 m, 3 m and 5 m respectively. It revealed resistivity values ranging from 7.3 Ωm to 300 Ωm for electrode spacing of 1.0 m; 13.8 Ωm to 200 Ωm for electrode spacing of 3 m and 3.9 Ωm to 200 Ωm for electrode spacing of 5 m at the first location. At the second location, it revealed resistivity values ranging from 0.53 Ωm to 120.0 Ωm for electrode spacing of 3 m and 0.30 Ωm to 100 Ωm for electrode spacing of 5 m. For electrode spacings of 1 m, 3 m and 5 m, resistivity values ranging from 6.1 Ωm to 600 Ωm, 12 Ωm to 600 Ωm and 0.85 Ωm to 1700 Ωm were obtained respectively at the third location. Generally, this study revealed lithologies composed of lateritic soil, sand, sandstone, sandyclay, clayeysand, weathered rock, fractured rock, clay and fresh basement; to a depth of about 39 m. Also, location 3 was discovered to have good groundwater prospects; though not as good as for locations 1 and 2. 相似文献
6.
The influence of solar‐induced thermal stresses on the mechanical weathering of rocks in humid mid‐latitudes 
下载免费PDF全文
下载免费PDF全文 Jennifer Aldred Martha Cary Eppes Kimberly Aquino Rebecca Deal Jacob Garbini Suraj Swami Alea Tuttle George Xanthos 《地球表面变化过程与地形》2016,41(5):603-614
The role of solar‐induced thermal stresses in the mechanical breakdown of rock in humid‐temperate climates has remained relatively unexplored. In contrast, numerous studies have demonstrated that cracks in rocks found in more arid mid‐latitude locations exhibit preferred northeast orientations that are interpreted to be a consequence of insolation‐related cracking. Here we hypothesize that similar insolation‐related mechanisms may be efficacious in humid temperate climates, possibly in conjunction with other mechanical weathering processes. To test this hypothesis, we collected rock and crack data from a total of 310 rocks at a forested field site in North Carolina (99 rocks, 266 cracks) and at forested and unforested field sites in Pennsylvania (211 rocks, 664 cracks) in the eastern United States. We find that overall, measured cracks exhibit statistically preferred strike orientations (47° ± 16), as well as dip angles (52° ± 24°), that are similar in most respects to comparable datasets from mid‐latitude deserts. There is less variance in strike orientations for larger cracks suggesting that cracks with certain orientations are preferentially propagated through time. We propose that diurnally repeating geometries of solar‐related stresses result in propagation of those cracks whose orientations are favorably oriented with respect to those stresses. We hypothesize that the result is an oriented rock heterogeneity that acts as a zone of weakness much like bedding or foliation that can, in turn, be exploited by other weathering processes. Observed crack orientations vary somewhat by location, consistent with this hypothesis given the different latitude and solar exposure of the field sites. Crack densities vary between field sites and are generally higher on north‐facing boulder‐faces and in forested sites, suggesting that moisture‐availability also plays a role in dictating cracking rates. These data provide evidence that solar‐induced thermal stresses facilitate mechanical weathering in environments where other processes are also likely at play. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
7.
Amit Mittal Rajiv Agarwal Md Sanam Suraj Monika Arora 《Astrophysics and Space Science》2018,363(5):109
This paper deals with the photo-gravitational restricted four-body problem (PR4BP) with variable mass. Following the procedure given by Gascheau (C. R. 16:393–394, 1843) and Routh (Proc. Lond. Math. Soc. 6:86–97, 1875), the conditions of linear stability of Lagrange triangle solution in the PR4BP are determined. The three radiating primaries having masses \(m_{1}\), \(m_{2}\) and \(m_{3}\) in an equilateral triangle with \(m_{2}=m_{3}\) will be stable as long as they satisfy the linear stability condition of the Lagrangian triangle solution. We have derived the equations of motion of the mentioned problem and observed that there exist eight libration points for a fixed value of parameters \(\gamma (\frac{m \ \text{at time} \ t}{m \ \text{at initial time}}, 0<\gamma\leq1 )\), \(\alpha\) (the proportionality constant in Jeans’ law (Astronomy and Cosmogony, Cambridge University Press, Cambridge, 1928), \(0\leq\alpha\leq2.2\)), the mass parameter \(\mu=0.005\) and radiation parameters \(q_{i}, (0< q_{i}\leq1, i=1, 2, 3)\). All the libration points are non-collinear if \(q_{2}\neq q_{3}\). It has been observed that the collinear and out-of-plane libration points also exist for \(q_{2}=q_{3}\). In all the cases, each libration point is found to be unstable. Further, zero velocity curves (ZVCs) and Newton–Raphson basins of attraction are also discussed. 相似文献
8.
The Middle Cambrian succession of the Parahio Valley in general and Debsakhad section in particular is dominated by trilobites. Genus Opsidiscus, along with other trilobite forms dominates the lower Middle Cambrian succession. In the present study two new species of Opsidiscus, Opsidiscus wadiai and Opsidiscus srikantiai are reported from the lower Middle Cambrian succession of Debsakhad section. The species were differentiated on their morphological features and their multivariate analysis. The multivariate analysis applied here is used as a supplement method to qualitative analysis in order to differentiate between the cranidial characters of Opsidiscus. The qualitative study of each species studied individually shows more or less close affiliation as is observed by different quantitative methods. The presence of Opsidiscus has a great stratigraphic significance in this region, as they first appear from informal Stage 5 of Series 3 and goes up to the Drumian Stage of Series 3 of the Cambrian System in the Debsakhad section, which helps to correlate this section with other well known sections of the Middle Cambrian. 相似文献
9.
Biodun Suraj Badmus Musa Olufemi Awoyemi Olukayode Dewunmi Akinyemi Ganiyu Adekunle Saheed Oluwaseun Tolutope Olurin 《Central European Journal of Geosciences》2013,5(3):387-393
Locations and depths to magnetic contacts were estimated from the total intensity magnetic field using the Horizontal Gradient Magnitude (HGM), Analytic Signal Amplitude (ASA) and Local Wavenumber (LWN) methods. Aeromagnetic data from the Ibadan area, in south-western Nigeria, were analyzed to estimate depths to magnetic sources as well as source locations. The minimum/maximum depth limits of the HGM and LWN are relatively close and comparable, while shallow source depths limits are greater than expected in the ASA method when compared with the HGM and LWN functions. 相似文献
10.
Waterlogging and flood hazards vulnerability and risk assessment in Indo Gangetic plain 总被引：4，自引：2，他引：2
The recurrent flooding during monsoon and subsequent waterlogging in the northern Bihar plains and the magnitude of losses
due to these hazards indicate the continuing vulnerability of the region to flood and waterlogging. Management of floods and
waterlogging hazards in highly flood-prone regions of India, including Bihar state has been largely response oriented with
little or no attention to mitigation and preparedness. This paper presents a method for spatial, Geographic Information Systems-based
assessment of flood and waterlogging vulnerability and risk in northern Bihar plains. Multitemporal satellite data was used
to evaluate the area statistics and dynamics of waterlogging over the period from 1975 to 2008. The flood proneness is evaluated
at district level with reference to flood inundation during a period from 1998 to 2008. Census data were used to examine the
socio-economic characteristics of the region through computation of population density, cultivators, agricultural labourers,
sex ratio, children in age group 0–6 years and literates. The geohazard map derived by combining area prone to waterlogging
and flood inundation was multiplied with socio-economic vulnerability map to derive the flood-waterlogging risk map of the
region. The result shows that flood and water-logging pose highest risk to the central districts in the northern Bihar plains
with 50.95% of the total area under high and very high risk. 相似文献