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161.
162.
Muthukumar Anbazhagi Dhanraj Loganathan Subramani Tamilselvan Raj Jayabalou Senthilkumar Kamatchiammal Rakesh Kumar 《洁净——土壤、空气、水》2007,35(2):167-171
Cryptosporidium is an enteric parasitic protozoan capable of causing chronic diarrhea. One of the most common modes of transmission is through faeces‐contaminated water. This study determines the distribution of Cryptosporidium oocysts for the first time in Chennai City's drinking water supply. 199 drinking water samples were collected from ten zones of the city. In the water samples Cryptosporidium, a common pathogenic protozoan of the gastrointestinal tract, has been analyzed physico chemically as well as microbiologically for heterotrophic organisms and total coliforms (TC). The studies revealed that three zones of the city were highly contaminated with coliforms and parasitic protozoa. A statistical analysis was done to find any correlation between heterotrophic organisms, total coliforms, and oocysts. Even though a positive correlation exists between oocysts and bacteriological parameters, a regression equation shows that heterotrophic plate count (HPC) and total coliforms were only 20% responsible for the presence of oocysts. The level of Cryptosporidium oocysts isolated from the water samples may present a public health hazard although no major outbreaks have so far been reported in Chennai City. Routine surveillance of water quality throughout the city is needed to curb the pollutants. 相似文献
163.
The dynamic problem in micropolar viscoelastic medium has been investigated by employing eigen value approach after applying
Laplace and Fourier transformations. An example of infinite space with concentrated force at the origin has been presented
to illustrate the application of the approach. The integral transforms have been inverted by using a numerical technique to
obtain the displacement components, force stresses, couple stress and microrotation in the physical domain. The results for
these quantities are given and illustrated graphically. 相似文献
164.
Groundwater samples collected from both open and bore wells in an area of about 270 km2 from Madras City, India, have been analyzed for major ions (HCO3, Cl, Si, Na, Ca, and Mg) and trace elements (As, Se, B, V, Cr, Fe, Co, Pb, Cu, Zn, Cd, Mn, Ni, Mo, and Ba). The study reveals that the quality of potable water has deteriorated to a large extent. Seawater intrusion into the aquifer has been observed in nearly 50 percent of the study area. The toxic elements (As and Se) have already exceeded the maximum permissible limits of drinking water in almost the entire city. A positive correlation of As and Se with other toxic metals such as V, Cr, Fe, B, etc., indicates that all these elements are anthropogenic in origin. Applying multivariate analysis, the source for trace elements in groundwater has been grouped into two major factors: pollution and mobilization factors. The groundwater in the study area is largely contaminated by organic effluents and reflects the intensity of pollution caused by the overlying soil sediment and rapid infiltration of the pollutants. 相似文献
165.
Nirmal Kumar Sinha 《Pure and Applied Geophysics》1969,73(1):47-59
Summary The aim of this paper is to study the propagation of love-type waves in a homogeneous half-space overlain by a heterogeneous crust with various types of heterogenety. Frequency equations are obtained in each of the cases and numerical calculations are done in some cases and the results thus obtained are compared with those done byJeffreys andMitra [3]2). 相似文献
166.
167.
Kishor Panjabi Pradeep Goel Prasad Daggupati Narayan Kumar Shrestha Rituraj Shukla 《水文科学杂志》2020,65(13):2224-2232
ABSTRACT In humid regions, surface runoff is often generated by saturation-excess runoff mechanisms from relatively small variable source areas (VSAs). However, the majority of the current hydrologic models are based on infiltration-excess mechanisms. In this study, the AGricultural Non-Point Source Pollution (AGNPS) model was used to integrate the VSA concept using topographic wetness index (TWI). Both the original and AGNPS-VSA models were evaluated for a small agricultural field in Ontario, Canada. The results indicate that the AGNPS-VSA model performed better than original model. The AGNPS-VSA model predicted that only the saturated portion of the field with higher TWI values produced runoff, whereas the original AGNPS model showed uniform hydrologic response from the entire field. The results of this study are important for accurately mapping the locations of VSAs. This new model could be a powerful tool in identifying critical source areas for applying targeted best management practices to minimize pollutant loads to receiving waters. 相似文献
168.
ABSTRACTSustainable intensification of existing cropland is one of the most viable options for meeting the escalating food demands of the ever-increasing population in the world. Accurate geospatial data about the potential single-crop (rice-fallows) areas is vital for policymakers to target the agro-technologies for enhancing crop productivity and intensification. Therefore, the study aimed to evaluate and understand the dynamics of rice-fallows in the Odisha state of India, using SAR (Sentinel-1) and Optical (Landsat OLI) datasets. This study utilized a decision-tree approach and Principal component analysis (PCA) for the segmentation and separation of different vegetation classes. The estimated overall accuracy of extracted rice-fallow maps was in the range of 84 to 85 percent. The study identified about 2.2, 2.0 and 2.1mha of Rice-Fallows in the years 2015–16, 2016–17, and 2017–18, respectively. The combined analysis (all three years) of rice-fallow maps identified about 1.34mha of permanent rice-fallows, whereas the remaining 0.6–0.8mha area was under the current-fallow category. About 50% of the total permanent rice-fallows were detected in the rainfed areas of Mayurbhanj, Bhadrak, Bolangir, Sundargarh, Keonjhar, Baleswar, Nawarangpur and Bargarh districts. The study also illustrated the time-series profiles of SMAP (soil moisture) datasets for the ten agroclimatic zones of the Odisha, which can be utilized (along with rice-fallow maps) for the selection of crop and cultivars (e.g. short or medium duration pulses or oilseeds) to target the rice fallows. The approach utilized in the current study can be scaled up in similar areas of South and South-east Asia and Africa to identify single-crop areas for targeting improved technologies for enhanced crop productivity and intensification. 相似文献
169.
The effect of ion–neutral collisions on the propagation of MHD waves and surface waves at a single magnetic interface is investigated. The dispersion equations for MHD waves in a partially ionized medium are derived. There are three damped propagating modes in a uniform unbounded medium: an Alfvén mode, and fast and slow modes. The damping of waves depends on both the collisional frequency and the ionization fraction. Wave damping increases as ionization fraction decreases. Surface waves are discussed in three cases: (a) the incompressible limit, (b) the low plasma, and (c) for parallel propagation. The incompressible limit leads to Alfvén surface waves in a partially ionized medium and the dispersion characteristics are similar to those obtained by Uberoi and Datta. In the low plasma of the Earth's auroral F region there are two damped propagating magnetoacoustic surface waves for =/3. There is only one damped surface mode for =/2, but no surface wave is able to propagate for =0°. For the case of parallel propagation (=0°) the results obtained in the absence of ion-neutral collisions are consistent with the results of Jain and Roberts. It is found that a three-mode structure of damped propagating waves occurs owing to ion–neutral collisions for a comparatively high ionization fraction. For the case of the solar photosphere, where the ionization fraction is low, two weakly damped surface waves are found, though the damping is almost negligible. The pattern of propagation is similar to that found in the case discussed by Jain and Roberts, but the wave speeds are lower due to ion–neutral collisions. The strong collisions tie the ion–neutral species together and reduce the damping. 相似文献
170.
Groundwater flow and solute transport at the Mourquong saline-water disposal basin, Murray Basin, southeastern Australia 总被引:5,自引:0,他引:5
Craig T. Simmons Kumar A. Narayan Juliette A. Woods Andrew L. Herczeg 《Hydrogeology Journal》2002,10(2):278-295
Saline groundwater and drainage effluent from irrigation are commonly stored in some 200 natural and artificial saline-water
disposal basins throughout the Murray-Darling Basin of Australia. Their impact on underlying aquifers and the River Murray,
one of Australia's major water supplies, is of serious concern. In one such scheme, saline groundwater is pumped into Lake
Mourquong, a natural groundwater discharge complex. The disposal basin is hydrodynamically restricted by low-permeability
lacustrine clays, but there are vulnerable areas in the southeast where the clay is apparently missing. The extent of vertical
and lateral leakage of basin brines and the processes controlling their migration are examined using (1) analyses of chloride
and stable isotopes of water (2H/1H and 18O/16O) to infer mixing between regional groundwater and lake water, and (2) the variable-density groundwater flow and solute-transport
code SUTRA. Hydrochemical results indicate that evaporated disposal water has moved at least 100 m in an easterly direction
and that there is negligible movement of brines in a southerly direction towards the River Murray. The model is used to consider
various management scenarios. Salt-load movement to the River Murray was highest in a "worst-case" scenario with irrigation
employed between the basin and the River Murray. Present-day operating conditions lead to little, if any, direct movement
of brine from the basin into the river.
Electronic Publication 相似文献