Identification of aquifer-recharge zones and sources in an urban development area (Delhi, India), by correlating isotopic tracers with hydrological features   总被引：1，自引：0，他引：1  

Manish Kumar  M. Someshwar Rao  Bhishm Kumar  Algappan Ramanathan 《Hydrogeology Journal》2011,19(2):463-474

Recharge zones and sources in an urban setup (NCT of Delhi, India) were identified using environmental isotopes (²H, ³H, ¹⁸O); they were then correlated with hydrogeological conditions. The isotopic results showed that groundwater is being recharged by surface water during the dry season, while recharge associated with local precipitation becomes prominent during the monsoon. The effect of source-water evaporation and altitude on the isotopic characteristics of groundwater was clearly noted. A gradual increase in groundwater age, i.e. decrease in tritium content, while moving away from the river/canals/drains, suggests a degree of mixing of old-aged groundwater with relatively young recharging water. Further, to substantiate the findings of isotopic investigations, surface recharge conditions were differentiated into potential pervious (recharge prone) and impervious (recharge resistant) surfaces through mapping of potential recharge areas based on soil type and water-table depth, to depict a three-dimensional illustration of hydrogeologically mediated recharge zones of the area. The hydrogeological evidence thus obtained about the spatial distribution of permeable zones, slope and boundary conditions, aptly substantiates the isotopic findings. The study seeks its impact by correlation of the isotopic findings with the regional groundwater flow regime which has been altered by the urban development.  相似文献   

A study of arsenic,iron and other dissolved ion variations in the groundwater of Bishnupur District,Manipur, India   总被引：1，自引：1，他引：0  

Jayalakshmi Devi Oinam  AL. Ramanathan  Anurag Linda  Gurmeet Singh 《Environmental Earth Sciences》2011,62(6):1183-1195

The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon (1–200 μg L⁻¹) as compared to pre-monsoon (1–108 μg L⁻¹) and monsoon (2–99 μg L⁻¹). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization (WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur area has an arsenic contamination problem, which is expected to increase in the near future.  相似文献   

Study of isotopic seasonality to assess the water source of proglacial stream in Chhota Shigri Glaciated Basin,Western Himalaya     

Naveen Kumar  Alagappan Ramanathan  Aman Arora  Mohd Soheb  Arindan Mandal  Parmanand Sharma  Shyam Ranjan 《水文研究》2020,34(5):1285-1300

The impact of surface melt patterns and the Indian summer monsoon (ISM) is examined on the varying contributions of end member (snow, glacier ice, and rain) to proglacial streamflow during the ablation period (June–October) in the Chhota Shigri glaciated basin, Western Himalaya. Isotopic seasonality observed in the catchment precipitation was generally reflected in surface runoff (supraglacial melt and proglacial stream) and shows a shift in major water source during the melt season. Isotopically correlated (δ¹⁸O–δD) high deuterium intercept in the surface runoff suggests that westerly precipitation acts as the dominant source, augmenting the other snow- and ice-melt sources in the region. The endmember contributions to the proglacial stream were quantified using a three-component mixing. Overall, glacier ice melt is the major source of proglacial discharge. Snowmelt is the predominant source during the early ablation season (June) and the peak ISM period (August and September), whereas ice melt reaches a maximum in the peak melt period (July). The monthly contribution of rain is on the lower side and shows a steady rise and decline with onset and retreat of the monsoon. These results are persistent with the surface melt pattern observed in Chhota Shigri glacier, Upper Chandra basin. Moreover, the role of the ISM in Chhota Shigri glacier is unvarying to that observed in other glacierized catchments of Upper Ganga basin. Thus, this study augments the significant role of the ISM in glacier mass balance up to the boundary of the central-western Himalayan glaciated region.  相似文献   

An analysis of the strong zonal circulation within the stratosphere of Venus     

V. Ramanathan  R.D. Cess 《Icarus》1975,25(1):89-103

A dynamical model is presented for the observed strong zonal circulation within the stratosphere of Venus. The model neglects rotational effects and considers a compressible and radiating atmosphere. It is shown that diurnal radiative heating is negligible within the lower stratosphere, a region below 85km, while observational evidence for the strong zonal circulation pertains to the lower stratosphere within which a direct thermal driving for the circulation is absent. The analysis, however, suggests that propagating internal gravity waves generated by diurnal solar heating of the upper stratosphere induce mean zonal velocities within the upper and lower stratosphere.Considering the linearized equations of motion and energy, and following Stern's (1971) analysis for an analogous problem, it is shown that the zonal velocity induced by internal gravity waves is retrograde in direction, a result which is in agreement with observation. The nonlinear equations of motion and energy are then solved by an approximate analytical method to determine the magnitude of the zonal velocity. This velocity increases from zero at the tropopause to about 200 msec^?1 at the 85 km level. The velocity near the uv-cloud level compares favorably with the observed value of 100 msec^?1.  相似文献   

Suspended sediment dynamics in the meltwater of Chhota Shigri glacier,Chandra basin,Lahaul-Spiti valley,India     

Virendra Bahadur Singh  AL. Ramanathan 《山地科学学报》2018,15(1):68-81

Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier, Himachal Pradesh, India for different melt seasons during the period 2011-2014. Maximum suspended sediment concentration in the meltwater was found during the month of July 2011, 2012 and 2014 constituting to 55.2%, 48.3% and 46.9%, respectively. Whereas in 2013, maximum suspended sediment concentration was observed in August accounting for 46.1% of the total. On the other hand, maximum suspended sediment load was monitored in the month of July 2011, 2012 and 2014 constituting 59.5%, 63% and 55.7% of the total, respectively. Whereas in 2013, maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load. Annual distribution of suspended sediment concentration (SSC) and suspended sediment load (SSL) in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013, which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods. Marked diurnal variation has been observed in the SSC of meltwater. Strong correlation was observed between SSC and SSL with discharge. On the other hand, SSC and SSL also showed strong exponential correlation with air temperature of the studied area. Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season (July and August) and low during the late melt season (September and October). The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1 mm/yr, which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot, Chorabari and Gangotri glaciers, which may be caused by its geological setting containing high erosion resistant rocks such as granite, granite gneiss and porphyritic granite.  相似文献   

A Web-based environmental decision support system (WEDSS) for environmental planning and watershed management   总被引：1，自引：0，他引：1  

Ramanathan?SugumaranEmail author  James C.?Meyer  Jim?Davis 《Journal of Geographical Systems》2004,6(3):307-322

  相似文献   

Electrokinetic retention, migration and remediation of nitrates in silty loam soil under hydraulic gradients   总被引：1，自引：0，他引：1  

Krishnapillai Manokararajah  Ramanathan Sri Ranjan   《Engineering Geology》2005,77(3-4):263-272

Contamination of groundwater by nitrates leaching from intensive agricultural and livestock operations have become a major concern for surrounding communities that use groundwater as their water supply. High levels of nitrate in drinking water poses a significant risk to human health, i.e., methaemoglobinaemia (“blue baby” syndrome).

The traditional pump-and-treat method is ineffective in medium to fine-textured agricultural soils due to the low hydraulic conductivity. This paper presents the results of a laboratory experiment investigating the feasibility of using electrokinetic treatment in retaining, accumulating, moving and remediating nitrates in a silty loam soil under hydraulic gradients.

A hydraulic gradient of 1.25 was applied to the horizontal soil columns to simulate a groundwater movement system. The study was performed in two stages. During the first stage of the experiment, the anode located at the inflow end of the columns was able to retard the movement of nitrates even under a hydraulic gradient of 1.25. After 15 days of flow, the effluent nitrate concentration in the control column rose to 90 mg l⁻¹ while no nitrates were detected in the effluent from columns subjected to the electrokinetic treatment.

After 15 days, the polarity of the electrodes was switched and this second stage lasted another 20 days. The cathode near the inflow end promoted the conversion of nitrates entering the column to other forms. The anode near the outflow end promoted the migration and accumulation of negatively charged nitrate ions towards the outflow end. By the 12th day, the nitrate concentrations in the electrokinetically treated columns were brought down to <5 mg NO₃-N l⁻¹. Electrokinetic treatment retarded nitrate movement against a hydraulic gradient of 1.25 and effectively restored a medium-textured soil contaminated with NO₃-N.

The NO₂-N level remained below 1 mg l⁻¹ throughout the experiment. The hydraulic conductivity varied between 1.0E–7 and 3.6E–7 m s⁻¹. The current requirement varied between 3 and 6 mA.  相似文献   

A comparative evaluation of groundwater suitability for irrigation and drinking purposes in two intensively cultivated districts of Punjab, India   总被引：8，自引：0，他引：8  

Manish Kumar  Kalpana Kumari  AL. Ramanathan  Rajinder Saxena 《Environmental Geology》2007,53(3):553-574

Punjab is the most cultivated state in India with the highest consumption of fertilizers. Patiala and Muktsar districts are two agricultural dominated districts of Punjab located in extreme south-east and south-west of the state. This paper highlights temporal variations of the groundwater quality and compares its suitability for irrigation and drinking purpose in these two districts. Water samples were collected in March and September 2003, representing the pre-monsoon and post-monsoon seasons, respectively. Water samples were analysed for almost all major cations, anions, dissolved heavy metals and turbidity. Parameters like sodium adsorption ratio, % sodium, residual sodium carbonate, total hardness, potential salinity, Kelley’s ratio, magnesium ratio, index of base exchange and permeability index were calculated on the basis of chemical data. A questionnaire was also used to investigate perception of villagers on taste and odour. Comparison of the concentration of the chemical constituents with WHO (world health organization) drinking water standards of 2004 and various classifications show that present status of groundwater in Patiala is better for irrigation and drinking purposes except for a few locations with a caution that it may deteriorate in near future. In Muktsar, groundwater is not suitable for drinking. Higher total hardness (TH) and total dissolved solids at numerous places indicate the unsuitability of groundwater for drinking and irrigation. Results obtained in this forms baseline data for the utility of groundwater. In terms of monsoon impact, Patiala groundwater shows dilution and flushing but Muktsar samples show excessive leaching of different chemical components into the groundwater leading to the enrichment of different anions and cations indicating pollution from extraneous sources. No clear correlation between the quality parameters studied here and perceived quality in terms of satisfactory taste response were obtained at electrical conductivity values higher than the threshold minimum acceptable value.  相似文献   

The atmosphere of Io     

S.H. Gross  G.V. Ramanathan 《Icarus》1976,29(4):493-507

Observations of Io suggest that it may have an atmosphere in which sodium vapor, ammonia, and nitrogen are important constituents. Several atmospheric models consisting of these gases are treated here. These are tested as a function of total content against the Pioneer 10 observations and for stability against escape. The results suggest that the atmosphere is very tenuous and that the interpretation of the ionosphere detected by Pioneer 10 by a static model may be inconsistent with the sodium cloud observations. It is postulated that ionization may also be escaping and that sodium may be comparable in content in the atmosphere with some molecular constituent such as NH₃ or N₂. Sodium and this molecular component then dominate the atmosphere. It is also suggested that particle precipitation contributes to heating of the atmosphere and to the production of ionization; furthermore, the difference between day- and nighttime ionospheres and possible trailing and leading side effects may relate to the nature of the particle energy distributions. These distributions may be the result of the peculiar interaction of Io with the Jovian magnetosphere.  相似文献   

Major ion composition and seasonal variation in the Lesser Himalayan lake: case of Begnas Lake of the Pokhara Valley, Nepal     

Udhab Raj Khadka  AL. Ramanathan 《Arabian Journal of Geosciences》2013,6(11):4191-4206

The Begnas Lake in the Pokhara Valley is one of the threatened habitats in Nepal. The major ion chemistry explains the status of most of the inorganic nutrients and their possible sources. However, the earlier studies mostly cover limnological investigations, and phytoplankton and zooplankton diversity. Thus, the present study has been conducted to investigate the geochemical processes and to examine the seasonal variation of chemical composition within Begnas Lake. The results showed that SO ₄ ^2- , PO ₄ ^3- , and NO ₃ ^- increased compared with the previous values. The domination of Ca²⁺, Mg²⁺, and HCO ₃ ^- explains the influence of carbonate weathering on the major ion concentration. In general, pH and dissolved oxygen decreased with the depth of water-column, while electric conductivity, total dissolved solids, HCO ₃ ^- , Cl^-, H₄SiO₄, K⁺, Mg²⁺, Ca²⁺, Mn²⁺, and Fe increased. Among the cations, the predominance of Ca²⁺ and Mg²⁺ as characterized by high (>0.6) (Ca²⁺ + Mg²⁺)/(Tz⁺) and (>0.8) (Ca²⁺ + Mg²⁺)/(Na⁺ + K⁺) equivalent ratios, also suggests prevalence of carbonate weathering. The low value of (Na⁺ + K⁺)/Tz⁺ ratio shows deficiency of Na⁺ and K⁺, suggesting low contribution of cations via aluminosilicate weathering. The C-ratio suggests a proton source derived both from oxidation of sulfide and dissolution and dissociation of atmospheric CO₂ during different seasons. Though the major hydro-chemical parameters are within permissible limit, the increase in trophic state of the lake suggests that inherent biogeochemical processes make the limiting nutrients available, rendering eutrophic effect. Therefore, further comprehensive studies incorporating sediment–water interaction ought to be carried out to explain the ongoing phenomena and curb the eutrophication process in the lake.  相似文献