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1.
River bank erosion control by soil nailing 总被引：2，自引：0，他引：2
A study has been done for analysing soil nailed cuts with circular type wedge failure by friction circle method. Various parameters
such as nail length, nail diameter, nail inclination, wall inclination and angle of internal friction of soil have been considered
to determine the factor of safety of nailed open cuts. The study shows that for cohesionless soil nailed cut, factor of safety
increase with increase of parameters like angle of internal friction of soil, length of nail (L) versus height of cut (H) ratio, cohesion of soil and nail inclination (upto 15°) with horizontal. The study revealed that nails grouted with cement
perform better than driven nails. A case study further confirms the analytical findings.
Received 7 October 相似文献
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Role of selected riparian herbs in reducing soil erosion and nutrient loss under simulated rainfall 总被引：3，自引：2，他引：1
The native riparian herbs such as Leonotis nepetaefolia (L.) R. Br., Cassia tora L., Ageratum conyzoides L., Parthenium hysterophorus L. and Sida acuta burm f., dominant on the bank of River Damodar in Eastern Jharia Area, Dhanbad (India), were selected to assess experimentally
their quantitative role in conserving the soil and reducing water runoff and nutrient (N and P) losses. A total of 42.5 mm
simulated rainfall were applied at 30 cm h−1 rain intensity on both vegetated and bare plots. The collected runoff water and eroded soil from each plot were determined
in terms of soil, water and nutrient conservation value (CV). Among the vegetated plots, soil CV ranged from 30 to 85% and
water CV from 20 to 48%. Nutrient (N and P) CV varied from 22 to 65% for total-N, 48 to 80% for ammonia-N and 50 to 86% for
nitrate-N. CV for total-P varied from 40 to 62%, inorganic-P from 42 to 60% and organic-P from 20 to 58%. In a stepwise multiple
regression equation comprising four independent variables (canopy cover, litter mass, soil moisture and plant biomass), canopy
cover explained 70–88% (P < 0.01) of variability in conserving soil, water and nutrient. The losses through runoff water and eroded soil from vegetated
plots were found to be minimized to a great extent as compared to bare plots. The role of these species in maintaining the
texture and fertility status of riparian soil is discussed. 相似文献
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Assessment of the potential for bank filtration in a water-stressed megacity (Delhi,India) 总被引：5，自引：3，他引：2
G. Lorenzen C. Sprenger T. Taute Asaf Pekdeger A. Mittal G. Massmann 《Environmental Earth Sciences》2010,61(7):1419-1434
In the densely populated semi-arid territory around Delhi, the water demand is rising continuously, while the surface- and
groundwater resources are threatened by contamination and overexploitation. This is a typical scenario in many newly industrialising
and developing countries, where new approaches for a responsible resources management have to be found. Bank filtration holds
a great potential, thus being a low tech method and benefiting from the storage and contaminant attenuation capacity of the
natural soil/rock. For this study, three field sites have been constructed to investigate bank filtration in different environments
in and around the megacity with a main focus on inorganic contaminants. Hydraulic heads, temperature gradients and hydrochemistry
of surface water and groundwater were analysed in three different seasons. Depending on site-specific conditions, distinct
hydrogeological conditions were observed and both positive and negative effects on water quality were identified. Most concerning
issues are the impact of anthropogenic ammonia, the mixing with ambient saline groundwater and the mobilisation of arsenic
during the reductive dissolution of manganese- and iron-(hydr)oxides. Positive aspects are the dilution of contaminants during
the mixing of waters from different sources, the sorption of arsenic, denitrification, and the precipitation of fluoride under
favourable conditions. 相似文献
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Satellite derived vegetation vigour has been successfully used for various environmental modeling since 1972. However, extraction of reliable annual growth information about natural vegetation (i.e., phenology) has been of recent interest due to their important role in many global models and free availability of time-series satellite data. In this study, usability of Moderate Resolution Imaging Spectro-radiometer (MODIS) and Global Inventory Modelling and Mapping Studies (GIMMS) based products in extracting phenology information about evergreen, semi-evergreen, moist deciduous and dry deciduous vegetation in India was explored. The MODIS NDVI and EVI time-series data (MOD13C1: 5.6 km spatial resolution with 16 day temporal resolution—2001 to 2010) and GIMMS NDVI time-series data(8 km spatial resolution with 15 day temporal resolution—2000 to 2006) were used. These three differently derived vegetation indices were analysed to extract and understand the vegetative growth rhythm over different regions of India. Algorithm was developed to derive onset of greenness and end of senescence automatically. The comparative analysis about differences in the results from these products was carried out. Due to dominant noise in the values of NDVI from GIMMS and MODIS during monsoon period the phenology rhythm were wrongly depicted, especially for evergreen and semi-evergreen vegetation in India. Hence, care is needed before using these data sets for understanding vegetative dynamics, biomass cestimation and carbon studies. MODIS EVI based results were truthful and comparable to ground reality. The study reveals spatio-temporal patterns of phenology, rate of greening, rate of senescence, and differences in results from these three products. 相似文献
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Natural Hazards - In this work, an attempt has been made to simulate strong ground motion of M w 5.4 earthquake in Kumaun region of Uttarakhand. The simulation is based on modified stochastic... 相似文献
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Nishant Mittal Joginder Sharma Vivek Tomar Udit Narain 《Planetary and Space Science》2009,57(1):53-57
We have analyzed the data for more than 12900 coronal mass ejections (CMEs) which were obtained by SOHO/LASCO during the period of 1996-2007. The online CME catalogue contains all major CMEs detected by LASCO C2 and C3 coronagraphs. Basically we determine the CME speeds from the linear and quadratic fits to the height-time measurements. It is found that linear (constant speed) fit is preferable for 90% of the CMEs. The distribution of speeds of CMEs in solar cycle 23 is presented along with those obtained by others. As expected, the speeds decrease in the decay phase of the cycle 23. There is an unusual drop in speed in the year 2001 and an abnormal increase in speed in the year 2003 due to the high concentration of CMEs, X-class soft X-ray flares, solar energetic particle (SEP) events and interplanetary shocks observed during October-November period called Halloween events. 相似文献
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Sudhir Mittal Asha Rani Rohit Mehra V. Balaram M. Satyanarayanan S. S. Sawant 《Journal of the Geological Society of India》2017,90(2):233-238
In the present study, analysis of 238U concentration in 40 drinking water samples collected from different locations of Jodhpur, Nagaur, Bikaner and Jhunjhunu districts of Rajasthan, India has been carried out by using high resolution inductively coupled plasma mass spectroscopy (HR-ICP-MS) technique. The water samples were taken from hand pumps and tube wells having depths ranging from 50 to 800 feet. The measured uranium concentration lies in the range from 0.89 to 166.89 μg l-1 with the mean value of 31.72 μg l-1. The measured uranium content in twelve water samples was found to be higher than the safe limit of 30 μg l-1 as recommended by World Health Organization (WHO, 2011) and US Environmental Protection Agency (USEPA, 2011). Radiological risk calculated in the form of annual effective dose estimated from annual uranium intake ranges from 0.66 to 138.63 μSv y-1 with the mean value of 26.28 μSv y-1. The annual effective dose in two drinking water samples was found to be greater than WHO (2004) recommended level of 100 μSv y-1. Chemical risk calculated in the form of lifetime average daily dose (LAAD) estimated from the water samples varies from 0.02 to 4.57 μg kg-1 d-1 with the mean value of 0.87 μg kg-1 d-1. The lifetime average daily dose (LAAD) of ten drinking water samples was found to be greater than WHO (2011) recommended level of 1 μg kg-1 d-1. The corresponding values of hazard quotient of 48% water samples were found to be greater than unity.A good positive correlation of uranium concentration with total dissolved solids (TDS) and conductance has been observed. However no correlation of uranium concentration with pH was observed. The results revels that uranium concentration in drinking water samples of the study area can cause radiological and chemical threat to the inhabitants. 相似文献
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Diffusional losses of amended anaerobic electron acceptors in sediment field microcosms 总被引：1，自引：0，他引：1
Menka Mittal 《Marine pollution bulletin》2010,60(8):1217-1225
Hudson River sediment microcosms from Piles Creek (PC), Piermont Marsh (PM), and Iona Island (II) were amended with ∼100 mM nitrate or sulfate to stimulate anaerobic bioremediation. Nitrate and sulfate decreased over two years of field incubation and the fraction of these losses due to diffusion to the water column was predicted using Fick’s law. Apparent diffusion (Dapp) values of 1-4 × 10−10 m2 s−1 predicted the majority of loss/gain from/to the sediments by 700 d, but not at all times. Effective diffusion (Deff) values predicted by the porosity function (Deff = Dmol ε4/3) were larger than those observed in the field, and field data indicates a cube power relationship: Deff = Dmol ε3. Dapp greatly increased in surficial layers at PM and PC in year two, suggesting that bioadvection caused by bioturbating organisms had occurred. The effects of bioturbation on transport to/from the sediments are modeled, and results can be applied to various sediment treatment scenarios such as capping. 相似文献