Spinel Ferrite Mediated Photo‐Fenton Degradation of Phenolic Analogues: A Detailed Study Employing Two Distinct Inorganic Oxidants          下载免费PDF全文

Rimi Sharma  Sonal Singhal 《洁净——土壤、空气、水》2018,46(1)

The present work demonstrates the applicability of ferrites as photo‐Fenton catalysts for deterioration of different phenolic derivatives. To analyze optimal reaction conditions, experiments are performed with four magnetic spinel ferrites MFe₂O₄ (M = Co, Cu, Ni, and Zn) and two inorganic oxidants, i.e., hydrogen peroxide (HP) and potassium peroxymonosulfate (PMS). The reactions are performed using p‐nitrophenol as phenolic probe. CuFe₂O₄ and CoFe₂O₄ possessed excellent ability to activate HP and PMS, respectively, among all four synthesized catalysts. A noteworthy aspect of two oxidizing agents is that the concentration of PMS used during the reaction is four times less than HP. Further, the broad pH activity of PMS provides a significant advantage over HP. The optimal reaction conditions, when HP is the oxidant in the photo‐Fenton degradation, are 0.50 g L^?1 MFe₂O₄, pH 2.5, and 8.8 mM HP. Although PMS is active in a wide pH range (2–10), adequate reaction conditions are 0.50 g L^?1 MFe₂O₄, natural pH, and 2.2 mM PMS. The photo‐Fenton activity of ferrites is extended to the degradation of different nitro‐ and chloro‐analogs of phenol (2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2,4‐dinitrophenol, 2,4,6‐trinitrophenol, 2‐chlorophenol, 3‐chlorophenol, 4‐chlorophenol, 2,4‐dichlorophenol) with only two ferrites (CuFe₂O₄ and CoFe₂O₄). A comparative study is performed with the two oxidants (HP and PMS) with positive results. Finally, stability and reusability of magnetic ferrites as catalysts are also studied to prove their use in phenolic solution treatment.  相似文献   

Trend and spatial distribution of rainfall & rainy days over Andaman & Nicobar Islands     

Naresh Kumar  B. P. Yadav  Ajit Tyagi  A. K. Jaswal 《Natural Hazards》2012,63(2):575-587

The present study examines the characteristics and climatological features of daily rainfall data over Andaman & Nicobar Islands. Analysis of rainfall data reveals a large monthly deviation over the northern latitudes as compare to southern latitudes of Andaman & Nicobar Islands. Also, it is found that rainfall increases from north to south latitudes in all the seasons except monsoon, where a reverse pattern exists. In trend analysis, a statistically significant decreasing trend (confidence level >95?%) is observed for yearly rainfall and rainy days over the region. Analysis of daily rainfall intensity for each year shows increasing trend for frequency of rather heavy rain (35.6?C64.4?mm) and significant decreasing trend for frequencies of light rain (2.5?C7.5?mm), and very heavy rain (>124.5?mm) over the region. Many times, very heavy rain events are associated with cyclonic disturbances affecting Andaman & Nicobar Islands region. The analysis of cyclonic disturbances over the region reveals a stronger and more significant decreasing trend. So, one of the causes for decreasing trend in very heavy rain over Andaman & Nicobar Islands may be due to significant decreasing frequency of cyclonic disturbances affecting this region.  相似文献   

Temporal divergence in cropping pattern and its implications on geospatial drought assessment     

C. S. Murthy  M. V.R. Sesha Sai  M. Naresh Kumar  P. S. Roy 《国际地球制图》2013,28(5):377-395

Time series data on cropping pattern at disaggregated level were analysed and its implications on geospatial drought assessment were demonstrated. An index of Cropping Pattern Dissimilarity (CP-DI) between a pair of years, developed in this study, proved that the cropping pattern of a year has a higher degree of similarity with that of recent past years only and tends to be dissimilar with longer time difference. The temporal divergence in cropping pattern has direct implications on geospatial approach of drought assessment, in which, time series NDVI data are compared for drought interpretation. It was found that, seasonal NDVI profiles of drought year and normal year did not show any anomaly when the cropping patterns were dissimilar and two normal years having dissimilar cropping pattern showed different NDVI profiles. Therefore, it is suggested that such temporal comparisons of NDVI are better restricted to recent past years to achieve more objective interpretation.  相似文献   

Crustal thickness and Poisson’s ratio variations across the northwest Himalaya and eastern Ladakh     

Devajit Hazarika  Naresh Kumar  Dilip Kumar Yadav 《Acta Geophysica》2013,61(4):905-922

Crustal thickness and Poisson’s ratios are estimated across the northwest (NW) Himalaya and eastern Ladakh applying H-k stacking method on receiver functions of teleseismic earthquakes recorded at 16 broadband seismological stations. The results show significant lateral variation of crustal thickness from the Lesser and Higher Himalaya (～50 km thick) to Ladakh (～80 km thick) through the Indus Tsangpo Suture Zone (ITSZ). The Indian Moho is continuously traceable across the ITSZ which is consistent with the underthrusting of the Indian plate beyond the surface collision boundary. The estimated Poisson’s ratios in the Lesser and Higher Himalaya are low (0.249–0.253), suggesting felsic composition of the crust. The Poisson’s ratio is intermediate in the Tethyan Himalaya (0.269–0.273) and high beneath Ladakh (0.280–0.303), indicating the effect of aqueous fluid/partial melt present in the crust.  相似文献   

Earthquake precursory research in western Himalaya based on the multi-parametric geophysical observatory data     

Naresh Kumar  Gautam Rawat  Vinay M. Choubey  Devajit Hazarika 《Acta Geophysica》2013,61(4):977-999

The opening of cracks and influx of fluids in the dilatancy zone of impending earthquake is expected to induce short-term changes in physical/chemical/hydrological properties during earthquake build-up cycle, which should be reflected in time-varying geophysical fields. With this rationale, eleven geophysical parameters are being recorded in continuous mode at the Multi-Parametric Geophysical Observatory (MPGO), in Ghuttu, Garhwal Himalaya, for earthquake precursory research. The critical analysis of various geophysical time series indicates anomalous behavior at few occasions; however, the data is also influenced by many external forces. These external influences are the major deterrent for the isolation of precursory signals. The recent work is focused on the data adoptive techniques to estimate and eliminate effects of solar-terrestrial and hydrological/environmental factors for delimiting the data to identify short-term precursors. Although any significant earthquake is not reported close to the observatory, some weak precursory signals and coseismic changes have been identified in few parameters related to the occurrence of moderate and strong earthquakes.  相似文献   

Historical temporal variation in precipitation over Western Himalayan Region: 1857-2006     

Naresh KUMAR  Ashok Kumar JASWAL 《山地科学学报》2016,13(4):672-681

This study has examined the temporal variation in monthly, seasonal annual precipitation over the Western Himalayan Region(WHR) and the influence of global teleconnections, like the North Atlantic Oscillation(NAO) and Southern Oscillation(SO) Indices on seasonal annual precipitation. The Mann–Kendall non-parametric test is applied for trend detection and the Pettitt–Mann–Whitney test is used to detect possible shift. Maximum entropy spectral analysis is applied to find the periodicity in annual seasonal precipitation. The study shows a non-significant decreasing trend in annual precipitation over WHR for the period 1857-2006. However, in seasonal precipitation, a significant decreasing trend is observed in monsoon and a significant increasing trend in post-monsoon season during the same period. The significant decrease in monsoon precipitation may be due to weakening of its teleconnection with NAO as well as SO Indices mainly during last three decades. It is observed that the probable change of year in annual monsoon precipitation over WHR is 1979. The study also shows significant periodicities of 2.3-2.9 years and of 3.9-4.7 years in annual seasonal precipitation over WHR.  相似文献   

Structural data extraction from stereographic or equal area projections using image processing     

Vaibhav Singhal  Surajit Misra  Saibal Gupta 《Journal of the Geological Society of India》2018,91(1):32-40

Structural orientation data from the field are commonly represented on stereographic or equal area projections, and the raw data are usually not accessible to other workers for integration into larger datasets or comparative study. We have developed a technique for retrieving raw planar structural data from the above projection types using image analysis techniques. The principle involves two steps: (i) conversion of the foliation pole plots in the image into Cartesian coordinates, and (ii) inversion of the data soobtained into a geographic reference frame. The process involves either scanning of the target projection, or cropping of the projection figure from a pdf file using image processing software, followed by tracing of the data points and generation of an image file that can be subsequently input into a MATLAB supported program, “StrucExtract”. The results from the program are displayed in the form of dips and dip directions. The program has been tested with synthetic and natural examples, and may be invaluable for retrieval of structural data from older structural literature.  相似文献   

Palynology in hydrocarbon exploration: High impact palynological studies in Western Offshore and Krishna-Godavari Basin     

Naresh C. Mehrotra  B. S. Venkatachala  P. N. Kapoor 《Journal of the Geological Society of India》2010,75(2):364-377

This paper presents an updated account of palynostratigraphic, source rock evaluation and palaeoenvironment data on Western Offshore and Krishna Godavari (K-G) Basins. Forty three dinoflagellate biohorizons have been identified in the Tertiary subsurface of Mumbai Offshore, facilitating a high resolution correlation of Oil bearing horizons. In K-G Basin integrated palynostratigraphic data and the composite general lithologies for the Mesozoic and Cenozoic have been presented in a tabular form; Eighty two dinoflagellate biohorizons have been identified. A very fine dinoflagellate based stratigraphic resolution has been achieved at most levels making it useful in geological modelling for hydrocarbon exploration in both Western Offshore and K-G Basin.  相似文献   

A toppled structure with sliding in the Siwalik Hills, midwestern Nepal   总被引：1，自引：0，他引：1  

Naresh Kazi Tamrakar  Shuichiro Yokota  Osamu Osaka   《Engineering Geology》2002,64(4):339-350

Not only the high mountainous regions but also the southern hilly regions of Nepal frequently suffer from landslides and debris flows. An interesting toppled structure with sliding was distinguished on an excavated slope facing the major highway in one such region, the Siwalik Hills. These hills are mostly composed of alternating beds of sandstones and mudstones of the Siwalik Group. A distinct contrast in the direction of dip of the strata was recognized on the excavated slope; the strata in the upper portion of the slope dipped southward, whereas those of the foot slope dipped northward. This indicated that toppling of strata had occurred. The northward direction of toppling and the angle and axis of rotation of the block were determined by examining the distribution of the attitudes of the strata.

Steeply dipping strata influenced by southward thrusting along the major tectonic line, contrasting rigidity between sandstone and mudstone, and rapid dissection by a river were the major causes of the toppling. The bottom surface of the toppled part dipped gently not only northward but also partially westward, showing that the toppled block slid westward after toppling. Evidence for tension cracking and scarplets on the top slope indicated that the block was still actively sliding.

Because steeply dipping sandstone and mudstone strata are widely distributed in the Siwalik Hills, similar structures are inferred to exist in many places. Therefore, the investigation of such slope structures is important, and their instability must be evaluated before road construction and excavation projects are carried out in Nepal.  相似文献   

A hydrogeophysical model of the relationship between geoelectric and hydraulic parameters of anisotropic aquifers   总被引：1，自引：0，他引：1  

R. Sinha  M. Israil  D. C. Singhal 《Hydrogeology Journal》2009,17(3):495-503

An electrical resistivity method has been used to determine aquifer parameters in the Ganga-Yamuna interfluve in northern India. An existing relationship between the geoelectrical and hydraulic parameters has been modified for the case of an anisotropic aquifer. The hydrogeological framework in the upper part of the Ganga-Yamuna interfluve is evaluated by using existing relationships between hydraulic parameters and geoelectrical parameters for alluvial aquifers. On the basis of aquifer geometry, the area has been divided into two hydraulic units: the western Yamuna flood plain and the Ganga flood plain towards the east. The resistivity data collected in parts of the study area are first interpreted in terms of true resistivity and thicknesses of subsurface layers. The electrical parameters (resistivity and thicknesses) are subsequently correlated with the available pumping test data. Distinct correlations between transmissivity and modified transverse resistance are obtained for the two hydraulic units. A four-parameter model consisting of hydraulic conductivity, modified longitudinal resistivity, modified transverse resistance and hydraulic anisotropy is presented for the anisotropic aquifer underlain by conductive fine grained sediments. The model has been validated at a number of locations, where aquifer parameters are known from pumping test data.  相似文献