Nitrate contamination in groundwater of Sopore town and its environs,Kashmir, India   总被引：2，自引：2，他引：0  

Imran A. Dar  Mithas A. Dar  K. Sankar 《Arabian Journal of Geosciences》2010,3(3):267-272

An attempt has been made in this research work to evaluate the concentration of nitrate in groundwater and its management in Apple town and its environs. Groundwater pollution has been reported in many aquifers because of high concentration of nitrate in ground water, which is the result of excessive use of fertilizers to cropland. Systematic sampling was done, with a view to understand the source of nitrate concentration in the study area. Fifteen sample sites were selected and the samples were taken for a baseline study to understand the geochemistry of the study area and to assess its physicochemical characteristics. The water quality parameters were investigated for summer (May, 2007) and winter (December, 2007) seasons and were compared with the standard values given by ICMR / WHO. The hydrochemical data of 15 samples indicates that the concentration of almost all parameters fall within the permissible limits except nitrate. Linear Trend Analysis on seasonal and annual basis clearly depicted that nitrate pollution in the study area is increasing significantly. About 85% of samples during summer season and 67% of the samples during winter season were showing a high concentration of nitrate, exceeding permissible limit of WHO (50 mg/l), which is due to the use of nitrogenous fertilizers in the study area. Appropriate methods for improving the water quality and its management in the affected areas have been suggested.  相似文献   

用陆地卫星TM6数据演算地表温度的单窗算法   总被引：263，自引：3，他引：263  

覃志豪 《地理学报》2001,56(4):456-466

陆地卫星 TM数据 (TM6)热波段表示地表热辐射和地表温度变化。长期以来 ,从 TM6数据中演算地表温度通常是通过所谓大气校正法。这一方法需要估计大气热辐射和大气对地表热辐射传导的影响 ,计算过程很复杂 ,误差也较大 ,在实际中应用不多。根据地表热辐射传导方程 ,推导出一个简单易行并且精度较高的演算方法 ,把大气和地表的影响直接包括在演算公式中。该算法需要用地表辐射率、大气透射率和大气平均温度 3个参数进行地表温度的演算。验证表明 ,该方法的地表温度演算较高。当参数估计没有误差时 ,该方法的地表温度演算精度达到 <0 .4℃ ,在参数估计有适度误差时 ,演算精度仍达 <1 .1℃。因该方法适用于仅有一个热波段的遥感数据 ,故称为单窗算法。  相似文献   

Early warning system for rainfall-triggered landslides based on real-time probabilistic hazard assessment     

Correa  Oscar  García  Francisco  Bernal  Gabriel  Cardona  Omar Darío  Rodriguez  Carlos 《Natural Hazards》2020,100(1):345-361

Natural Hazards - A methodology to define rainfall-landslide thresholds, using a probabilistic model in which the accumulated rainfall at any time is treated as a random variable, is proposed. The...  相似文献   

Chukchi Sea Ice Conditions for the Last Few Centuries: Reconstruction from Sedimentation Records     

A. S. Astakhov  V. A. Akulichev  A. V. Dar’in  I. A. Kalugin  Yanguang Liu  V. V. Babich  A. A. Bosin  E. G. Vologina  V. V. Plotnikov 《Doklady Earth Sciences》2018,480(2):767-772

For the first time, the reconstruction of variations in the duration over several hundred years was conducted on the basis of models developed by comparing hydrometeorological observations and detailed scanning of the chemical composition of bottom sediments accumulated during the corresponding period. The gauge models for the reconstruction of air temperature and ice cover of the water area for three sites in the northern part of the Chukchi Sea have been developed. During the reconstruction, an insignificant increase in the duration of the ice-free period during the Little Ice Age was established, which does not coincide with the changes in the temperature regime that took place. It is concluded that the dynamics of the inflow of warm Pacific waters through the Bering Strait had the predominant influence on the ice regime of the Chukchi Sea.  相似文献   

Geophysical signatures resolving hydrogeological complexities over hard rock terrain—a study from Southern India   总被引：1，自引：0，他引：1  

Sahebrao Sonkamble  Subash Chandra  E. Nagaiah  Farooq A. Dar  V. K. Somvanshi  Shakeel Ahmed 《Arabian Journal of Geosciences》2014,7(6):2249-2256

A series of geophysical parameters have been applied with geological perception to resolve the hydrogeological complexities over granitic terrain at Hyderabad, India. Frequent failure of borehole drillings and the thrust conditions of community have prompted a noninvasive suitable tool, applied at small scale for pinpointing potential well site. Geophysical scanning, viz. electrical resistivity tomography (ERT), spontaneous potential (SP), and electrical gradient profiling (GP) were employed within the restricted space of housing complex to obtain the true characteristics of the subsurface lithology, where anomalies by the underground utility structures have been nullified. Results showed, in ERT, the low order of resistivity range 123 to 200?Ωm showing a plume like weathered zone underlain by sudden slip of massive granite (>217?Ωm) was of great interest to proceed further in the process. Here, the switchover in SP value from +18 mV to ?17 mV and GP from mean value 10 to 90 mV/m was recorded. The anomalies in SP and GP were precisely coincided with the ERT where upcoming of subsurface massive granite next to the inferred fracture was noted. Drilling core logs satisfies the geophysical signatures ensuring the inferred saturated fracture with the total yield 1,302 gal/h.  相似文献   

The street as urban icon? Tel Aviv’s Rothschild Boulevard     

Arnon Golan 《Urban geography》2013,34(5):721-734

In this article, I analyze Tel Aviv’s Rothschild Boulevard as an example of an urban symbol and suggest that while main streets, avenues and boulevards are usually perceived as integral parts of the urban symbolic ecology, they are rarely considered as exclusive urban icons in their own right. Although prestige of “privileged” streets influences reputations of cities and constitutes an important part of their imaginary, their complicated physical structure and multifunctional character conflict with their iconic status. The physical nature of streets resists configuration and articulation as exclusive, durable urban icons because symbols are generally conspicuous physical objects that can be directly interpreted and rendered as iconic.  相似文献   

Hydrochemistry of groundwater of Thiruporur block, Tamil Nadu (India)     

Imran Ahmad Dar  K. Sankar  Syed Tanzeem Shafi  Mithas Ahmad Dar 《Arabian Journal of Geosciences》2012,5(2):259-262

An attempt has been made in this work to evaluate the environmental chemistry of groundwater in Thiruporur block, Kancheepuram District, Tamil Nadu, India. Eleven villages of Thiruporur block were selected; where the people use groundwater for drinking purpose, and the water samples were subjected to systematic analysis with a view to understand the potability of drinking water sources. The depth of the bore wells varied from 100 to 200?feet. The values obtained for different parameters were compared with the standard values given by ISI/ICMR/WHO and the variations were notable for the parameters like nitrate and total hardness for few samples. Therefore, a medical survey was carried out to study the harmful effects on the society due to these two parameters at the villages??Kayar and Melkottaiyar.  相似文献   

Partition of arsenic in soils sediments and the origin of naturally elevated concentrations in groundwater of the southern pampa region (Argentina)     

María del Carmen Blanco  Juan Darío Paoloni  Hector Morrás  Carmen Fiorentino  Mario Eduardo Sequeira  Nilda N. Amiotti  Oscar Bravo  Silvana Diaz  Martín Espósito 《Environmental Earth Sciences》2012,66(7):2075-2084

Excessive arsenic concentrations above the Argentinean and WHO guidelines for drinking water (10 μg L⁻¹) affects shallow aquifers of the southern Pampean Plain (Argentina) hosted in the Pampean and the Post Pampean formations (loess and reworked loess; Plio-Pleistocene–Holocene). Health problems related to high As concentrations in drinking waters are known as Endemic Regional Chronic Hydroarsenicism. Hydrochemistry of shallow groundwaters and soil geochemistry were investigated aiming to (1) understand the partition of As in the solid phase and its relationship with unacceptable As concentrations in waters, (2) identify the provision source of As to groundwaters. Only 5% of the samples had As concentrations <10 μg L⁻¹; in 27% As concentrations ranged from 10 to 50 μg L⁻¹ and in 58% it reached 60–500 μg L⁻¹. The coarse fraction (50–2,000 μm) hosts about 27% of the total As in the solid phase, being positively correlated to Ba (p < 0.01; r ² = 0.93). About 70% is included in the <2 μm fraction and had positive correlations of As–Fe (p < 0.05; r ² = 0.85) and As–Cr (p < 0.05; r ² = 0.68). Soils and sediment sand fractions of vadose zones are the primary sources of As in shallow groundwater while adsorption–desorption processes, codisolution–coprecipitation, and evaporation during the dry seasons raise As concentrations in waters exceeding the guideline value for drinking water.  相似文献   

Geochemistry of phosphate bearing sedimentary rocks in parts of Sonrai block,Lalitpur District,Uttar Pradesh,India     

K.F. Khan  Shamim A. Dar  Saif A. Khan 《Chemie der Erde / Geochemistry》2012,72(2):117-125

Major, trace and rare earth elements of phosphatic rocks around Sonrai block of Paleo-Mesoproterozoic age having phosphatic breccia, quartzite, shale, sandstone, limestone and ironstone, have been determined to evaluate their correlation, relationship with the phosphorus content, the nature of possible substitution of various elements and regional distribution pattern over the area. The study indicates that the number of elements is substituted in the apatite structures; few of them are associated with phosphate and carbonate minerals. The variable concentration of major, trace and rare earth elements in the phosphatic rocks has been influenced by various physico-chemical processes involved during weathering and leaching of the source rocks. The distribution of the major, trace and rare earth elements is controlled by the environmental variations in the sediment water interface. The majority of trace elements were mainly influenced by the principle adsorbents like the phosphate minerals in addition to clay, iron oxides and silicate minerals. The PAAS normalized REE patterns of Sonrai block of phosphorites are characterized by negative Ce anomalies and Positive Eu anomalies. It is inferred from the distribution and interrelationship of major, trace and rare earth elements that the deposition of phosphate minerals might have occurred in highly oxidizing to slightly reducing conditions in supratidal to intertidal continental margins and shallow marine environment. The deposition was controlled by marine upwelling leading to excess charge of phosphate in certain zones of phosphogenic basins, lithologic facies variations in restricted circulations of basinal waters and electrochemical factors such as negative Eh, pH and other factors, which influenced the deposition of phosphates. The replacement, precipitation in voids and fissures and diagenesis were also important mechanisms of phosphate generation in Sonrai basin. The main source for various elements may be the minerals of cratonic mass of Bundelkhand Granitic Complex, a basement of Bijawar Basin, which also provided land derived phosphorus through weathering of the terrestrial cover.  相似文献   

Spectrally based remote sensing of river bathymetry   总被引：1，自引：0，他引：1  

Carl J. Legleiter  Dar A. Roberts  Rick L. Lawrence 《地球表面变化过程与地形》2009,34(8):1039-1059

This paper evaluates the potential for remote mapping of river bathymetry by (1) examining the theoretical basis of a simple, ratio‐based technique for retrieving depth information from passive optical image data; (2) performing radiative transfer simulations to quantify the effects of suspended sediment concentration, bottom reflectance, and water surface state; (3) assessing the accuracy of spectrally based depth retrieval under field conditions via ground‐based reflectance measurements; and (4) producing bathymetric maps for a pair of gravel‐bed rivers from hyperspectral image data. Consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate: the remotely sensed signal must be dominated by bottom‐reflected radiance. We developed a simple algorithm, called optimal band ratio analysis (OBRA), for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong, linear relationships between an image‐derived quantity X and flow depth d. OBRA of simulated spectra indicated that water column optical properties were accounted for by a shorter‐wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer‐wavelength denominator band subject to strong absorption by pure water. Field spectra suggested that bottom reflectance was fairly homogeneous, isolating the effect of depth, and that radiance measured above the water surface was primarily reflected from the bottom, not the water column. OBRA of these data, 28% of which were collected during a period of high turbidity, yielded strong X versus d relations (R² from 0·792 to 0·976), demonstrating that accurate depth retrieval is feasible under field conditions. Moreover, application of OBRA to hyperspectral image data resulted in spatially coherent, hydraulically reasonable bathymetric maps, though negative depth estimates occurred along channel margins where pixels were mixed. This study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献