Size distribution and roundness of clasts within pseudotachylytes of the Gangavalli Shear Zone,Salem, Tamil Nadu: An insight into its origin and tectonic significance     

Bhuban Mohan Behera  V Thirukumaran  Aishwaraya Soni  Prasanta Kumar Mishra  Tapas Kumar Biswal 《Journal of Earth System Science》2017,126(4):46

Gangavalli (Brittle) Shear Zone (Fault) near Attur, Tamil Nadu exposes nearly 50 km long and 1–3 km wide NNE–SSW trending linear belt of cataclasites and pseudotachylyte produced on charnockites of the Southern Granulite Terrane. Pseudotachylytes, as well as the country rock, bear the evidence of conjugate strike slip shearing along NNE–SSW and NW–SE directions, suggesting an N–S compression. The Gangavalli Shear Zone represents the NNE–SSW fault of the conjugate system along which a right lateral shear has produced seismic slip motion giving rise to cataclasites and pseudotachylytes. Pseudotachylytes occur as veins of varying width extending from hairline fracture fills to tens of meters in length. They carry quartz as well as feldspar clasts with sizes of few mm in diameter; the clast sizes show a modified Power law distribution with finer ones (<1000 \({\upmu }\)m\(^{2})\) deviating from linearity. The shape of the clasts shows a high degree of roundness (>0.4) due to thermal decrepitation. In a large instance, devitrification has occurred producing albitic microlites that suggest the temperature of the pseudotachylyte melt was >1000\(^{\circ }\hbox {C}\). Thus, pseudotachylyte veins act as a proxy to understand the genetic process involved in the evolution of the shear zone and its tectonic settings.  相似文献   

Numerical simulation of physical and dynamical characteristics associated with the severe thunderstorm on April 5, 2015 at Kushtia and Jhenaidah     

Samarendra Karmakar  Dewan Abdul Quadir  Mohan Kumar Das 《Natural Hazards》2017,86(3):1127-1146

The paper deals with the study of the physical and dynamical characteristics of a severe thunderstorm, which had occurred on April 5, 2015, at about 2100 UTC in the southwestern Bangladesh with location around 23.3–23.7N and 89.0–89.4E within the upazilas (sub-districts) of Kumarkhali and Shailkupa under the districts of Kushtia and Jhenaidah, respectively. The thunderstorm was associated with numerous hails of large size. More than 5000 birds which used to live in the bird sanctuary at Shailkupa and 22,011 birds in Chhaglapara Bird Sanctuary of Kumarkhali died as they were hit by the hails. Large hails also damaged crops, houses and forests over the thunderstorm hit areas. The evolution of the thunderstorm is studied by the WRF model, which is initialized using the National Centers for Environmental Prediction Final reanalysis data of 0000 UTC of April 5, 2015. The simulated results provide a basis to study the physical and dynamical characteristics of the thunderstorm, which are generally not identified by the meteorological observations which are too sparse. The model has captured a micro-low over Kumarkhali and its neighborhood, which favored the occurrence of the severe thunderstorm. The model simulated rainfall is about 26 mm near the place of occurrence, which matches well with the area where the reflectivity of hydrometeor is maximum. The convective available potential energy is found to be 1600 J kg^?1 at 1730 UTC near the place of occurrence of the thunderstorm; this indicates high atmospheric instability over the thunderstorm location for the formation of the thunderstorm. The vertical velocity, convergence, cloud water mixing ratio and the ice water mixing ratio and their vertical extensions are found to be satisfactory and responsible for the occurrence of large hails associated with the thunderstorm.  相似文献   

Decadal glacial lake changes in the Koshi basin,central Himalaya,from 1977 to 2010, derived from Landsat satellite images     

Finu Shrestha  Xiao Gao  Narendra Raj Khanal  Sudan Bikash Maharjan  Rajendra Bahadur Shrestha  Li-zong Wu  Pradeep Kumar Mool  Samjwal Ratna Bajracharya 《山地科学学报》2017,14(10):1969-1984

Changes in glacial lakes and the consequences of these changes, particularly on the development of water resources and management of glacial lake outburst flood(GLOF) risk, has become one of the challenges in the sustainable development of high mountain areas in the context of global warming. This paper presents the findings of a study on the distribution of, and area changes in, glacial lakes in the Koshi basin in the central Himalayas.Data on the number of glacial lakes and their area was generated for the years 1977, 1990, 2000, and 2010 using Landsat satellite images. According to the glacial lake inventory in 2010, there were a total of 2168 glacial lakes with a total area of 127.61 km~2 and average size of 0.06 km~2 in the Koshi basin. Of these,47% were moraine dammed lakes, 34.8% bedrock dammed lakes and 17.7% ice dammed lakes. The number of glacial lakes increased consistently over the study period from 1160 in 1977 to 2168 in 2010, an overall growth rate of 86.9%. The area of glacial lakes also increased from 94.44 km~2 in 1977 to 127.61 km~2 in 2010, a growth rate of 35.1%. A large number of glacial lakes in the inventory are small in size(≤ 0.1km~2). End moraine dammed lakes with area greater than 0.1 km~2 were selected to analyze the change characteristics of glacial lakes in the basin. The results show that, in 2010, there were 129 lakes greater than 0.1 km~2 in area; these lakes had a total area of 42.92km~2 in 1997, increasing to 63.28 km~2 in 2010. The distribution of lakes on the north side of the Himalayas(in China) was three times higher than on the south side of the Himalayas(in Nepal).Comparing the mean growth rate in area for the 33 year study period(1977-2010), the growth rate on the north side was found to be a little slower than that on the south side. A total of 42 glacial lakes with an area greater than 0.2 km~2 are rapidly growing between 1977 and 2010 in the Koshi basin, which need to be paid more attention to monitoring in the future and to identify how critical they are in terms of GLOF.  相似文献   

Mycorrhizal Colonization Affects the Survival of Vetiveria zizanioides (L.) Nash Grown in Water Containing As(III)     

Jatin Srivastava  Dinesh Shukla  Vishal Chand  Ram Naraian  Harish Chandra  Anant R. Nautiyal 《洁净——土壤、空气、水》2010,38(8):771-774

The presence of arsenic (As) in water is of great public concern. Arsenic exists in three common valence states viz., As(0) metalloid arsenic, As(III) (arsenite) and As(V) (arsenate). Arsenite [As(III)] is the most toxic form among arsenicals which, predominates in anaerobic conditions, generally in flooded soils and in the water with high BOD. Experiments were conducted to investigate the effect of As(III) on the mycorrhization in vetiver (Vetiveria zizanioides (L.) Nash) grass in hydroponics. Studies showed significant alteration in the mycorrhizal colonization in the roots of vetiver exposed to higher concentrations of As(III) starting from 1.0, 2.0, 3.0, 4.0 to 5.0 mg/L prepared in 5% Hoagland nutrient solution without addition of phosphate ions. Considerable reduction in the mycorrhizal intensity (M) was observed in all the treatment sets as compared to the control suggesting a negative impact of the As(III) on the mycorrhizal association. Simultaneously, the study also showed that, As(III) is toxic to the vetiver plants having mycorrhizal association however plants with non‐mycorrhizal (cleansed) roots were found to be able to survive for a longer period exposed to As(III).  相似文献   

Assessing strategic water availability using remote sensing,GIS and a spatial water budget model: case study of the Upper Ing Basin,Thailand     

Krishna Bahadur KC 《水文科学杂志》2013,58(6):994-1014

Abstract

This paper assesses strategic water availability and use under different development pathways on a basin scale using remote sensing (RS), geographical information systems (GIS) and a spatial water budget model (SWBM). The SWBM was applied to the Upper Ing Basin in northern Thailand to investigate the spatial and temporal variations in the location of streams and water yields from different parts of the basin. The base simulation was carried out for the years 1998–2007 using a DEM and actual land-use data at 100-m resolution. The simulated stream network was compared with topographic maps under different flow conditions, which were successfully represented. The 10-year average simulated river flow rate was 1300 L/s, but it more than doubled during periods of heavy rainfall and decreased below 600 L/s in dry seasons. The total length of the streams (based on flow threshold of 25 L/s) on a typical day in the dry season differed by a factor of approx. 1.5. Agricultural water needs and possible extraction were assessed and presented by dividing the basin into 10 different zones based on the stream network. The results show that there is the potential for harvesting significant quantities of water at different spatial gradients with no initial water supply for irrigation. Monthly water yields for each zone were computed; the results varied from less than 50% to over 137% of the per hectare water yield for the entire basin. This variation was due to differences in topography and land cover. The impact of land use and climate change on streamwater availability was also studied. The basin shows very different hydrological responses. The changes in average river flow relative to the base simulation were +27.6%,??32.1%, +94% and +52.9% under deforestation, changing land use from paddy field to orchard, bare soil and increased rainfall scenarios, respectively.

Citation Bahadur KC, K. (2011) Assessing strategic water availability using remote sensing, GIS and a spatial water budget model: case study of the Upper Ing Basin, Thailand. Hydrol. Sci. J. 56(6), 994–1014.  相似文献   

Trace gases and PM2.5-bound metal abundance over a tropical urban environment,South India     

M  Abdul Shukkur  V.G  Gopikrishna  N.G  Vishnu  Mohan  Mahesh 《Journal of Atmospheric Chemistry》2021,78(3):193-208

Pre and Post-Monsoon levels of ambient SO₂, NO₂, PM_2.5 and the trace metals Fe, Cu, etc. were measured at industrial and residential regions of the Kochi urban area in South India for a period of two years. The mean PM_2.5, SO₂ and NO₂ concentrations across all sites were 38.98?±?1.38 µg/m³, 2.78?±?0.85 µg/m³ and 11.90?±?4.68 µg/m³ respectively, which is lower than many other Indian cities. There was little difference in any on the measured species between the seasons. A few sites exceeded the NAAQS (define acronym and state standard) and most of the sites exceeded WHO (define acronym and state standard) standard for PM_2.5. The average trace metal concentrations (ng/m³) were found to be Fe (32.58)?>?Zn (31.93)?>?Ni (10.13)?>?Cr (5.48)?>?Pb (5.37)?>?Cu (3.24). The maximum concentration of trace metals except Pb were reported in industrial areas. The enrichment factor, of metals relative to crustal material, indicated anthropogenic dominance over natural sources for the trace metal concentration in Kochi’s atmosphere. This work demonstrates the importance of air quality monitoring in this area.

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Tropical cyclone contribution to extreme rainfall over southwest Pacific Island nations     

Deo  Anil  Chand  Savin S.  Ramsay  Hamish  Holbrook  Neil J.  McGree  Simon  Magee  Andrew  Bell  Samuel  Titimaea  Mulipola  Haruhiru  Alick  Malsale  Philip  Mulitalo  Silipa  Daphne  Arieta  Prakash  Bipen  Vainikolo  Vaiola  Koshiba  Shirley 《Climate Dynamics》2021,56(11):3967-3993

Southwest Pacific nations are among some of the worst impacted and most vulnerable globally in terms of tropical cyclone (TC)-induced flooding and accompanying risks. This study objectively quantifies the fractional contribution of TCs to extreme rainfall (hereafter, TC contributions) in the context of climate variability and change. We show that TC contributions to extreme rainfall are substantially enhanced during active phases of the Madden–Julian Oscillation and by El Niño conditions (particularly over the eastern southwest Pacific region); this enhancement is primarily attributed to increased TC activity during these event periods. There are also indications of increasing intensities of TC-induced extreme rainfall events over the past few decades. A key part of this work involves development of sophisticated Bayesian regression models for individual island nations in order to better understand the synergistic relationships between TC-induced extreme rainfall and combinations of various climatic drivers that modulate the relationship. Such models are found to be very useful for not only assessing probabilities of TC- and non-TC induced extreme rainfall events but also evaluating probabilities of extreme rainfall for cases with different underlying climatic conditions. For example, TC-induced extreme rainfall probability over Samoa can vary from ~ 95 to ~ 75% during a La Niña period, if it coincides with an active or inactive phase of the MJO, and can be reduced to ~ 30% during a combination of El Niño period and inactive phase of the MJO. Several other such cases have been assessed for different island nations, providing information that have potentially important implications for planning and preparing for TC risks in vulnerable Pacific Island nations.

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Possible evidence of remotely triggered and delayed seismicity due to the 2001 Bhuj earthquake (Mw?=?7.6) in western India     

G. Surve  G. Mohan 《Natural Hazards》2012,64(1):299-310

Remote triggering by large earthquakes at regional distances is a globally observed phenomenon. However, there are no reports of observations of dynamic triggering at regional distances of several source lengths associated with the large Mw?=?7.6 Bhuj earthquake of January 26, 2001, in western India. In the present study, a swarm of over 140 microearthquakes that occurred about 500?km southeast of Bhuj, in the geothermal province of the Western Ghats in the Deccan volcanic province (DVP) of India, immediately after the occurrence of the Bhuj earthquake in 2001 is investigated. The post-Bhuj seismicity (M?<?2.0) occurred in three bursts spread over 2?months with each burst of intense activity lasting for 2?C3?days. All the three bursts of seismicity occurred in the same volume along a 5-km-long NW?CSE trending fault. The temporal coincidence and the sudden rise in seismicity that interrupts the characteristically low background seismicity strongly suggest that the Bhuj earthquake may have remotely triggered this activity. The triggered seismicity began approximately 2.5?h after the onset of the Bhuj mainshock and continued well after the passage of the surface waves, suggesting that the dynamic stresses possibly gave rise to secondary time-dependent mechanisms leading to the triggering. It is proposed that the triggered and delayed seismicity is possibly a consequence of the redistribution in pore fluid pressure due to the Bhuj earthquake. This is the first documented observation of remotely triggered seismicity at regional distances due to the Bhuj earthquake.  相似文献   

Biosorptive behaviour of mango leaf powder and rice husk for arsenic(III) from aqueous solutions     

S. Kamsonlian  S. Suresh  V. Ramanaiah  C. B. Majumder  S. Chand  A. Kumar 《International Journal of Environmental Science and Technology》2012,9(3):565-578

The present study deals with the biosorption of As(III) from aqueous solution using mango leaves powder (MLP) and rice husk (RH) in a batch operation. Scanning electron microscopy and Fourier transformation infrared spectrometry analysis shows the surface texture of biosorbents and metal binding of functional groups of before and after biosorption of As(III). The optimum pH was obtained at 7 and 6 with 7 and 6?g/l of dosage of MLP and RH, respectively. The adsorption of As(III) onto MLP and RH was favourably influenced by an increase in temperature. Equilibrium data were well represented by the Freundlich isotherm model. Nitric acid and ethylenediaminetetra acetic acid was found to be a better eluant for the desorption followed by hydrochloric acid and sodium hydroxide of As(III) with a maximum desorption efficiency of 69.5, 48.5 and 79.4, 86.3?%, respectively. The pseudo-second-order kinetic model was found to best fitted of the experimental data over the equilibrium time at 32?h. The positive values of heat of adsorption (23.89?kJ/mol for MLP and 52.26?kJ/mol for RH) indicate the endothermic nature of the adsorption process. The thermodynamic study showed the spontaneous nature of the sorption of As(III) onto MLP and RH.  相似文献   

Assessment of heavy metal pollution in lake sediments of Katedan Industrial Development Area,Hyderabad, India     

P. K. Govil  J. E. Sorlie  D. Sujatha  A. K. Krishna  N. N. Murthy  K. Rama Mohan 《Environmental Earth Sciences》2012,66(1):121-128

Spatial distribution and temporal trends studies were carried out at Katedan Industrial Development Area (KIDA) near Hyderabad, capital of Andhra Pradesh state, India under Indo-Norwegian Institutional Cooperation Program, to find out the extent of contamination in streams and lake sediments from the discharge of industrial effluents. Stream and lake sediment samples were collected from the five lakes in the study area and connecting water streams. The samples were analyzed by XRF spectrometer for toxic elements. The studies reveal that the stream sediments with in the KIDA and the impounded Noor Mohammed Lake down stream have high concentration of some of the toxic elements like chromium, nickel, lead, arsenic, zinc etc. The geology of the area indicates that the study area consists of residual soil of acidic rocks, which are predominantly of Archaean gneisses and granites having low to medium concentrations of chromium and nickel. The source of these high concentration of elements like lead 2,300 mg/kg, copper 1,500 mg/kg, arsenic 500 mg/kg, chromium 500 mg/kg etc. cannot be derived from the surrounding acidic rocks and may be attributed to the industrial effluents released in the ditches and random dumping of hazardous solid waste. It was observed that the metal concentrations increased in the streams during the dry season (pre-monsoon period). After the monsoon rains, the metal concentrations in the streams were reduced by half which may be due to dilution. The eroded sediments are deposited in the lake where very high concentrations were encountered. Overflowing of the lake will spread the contamination further downstream. The lake sediments will remain as a major source of contamination by desorption to the water phase regardless of what happens to the effluent discharge in the KIDA. However, some samples showed enrichment of lead, arsenic and nickel during post-monsoon, which were collected near the dumpsite due to the leaching of toxic elements from the dump site to the lakes. Some of the toxic elements like nickel and copper have not shown any dilution but have increased after the rains, which could be due to the leaching of arsenic from the dumpsite to the lake along with rainwater. Geochemical maps showing the distribution of heavy/trace elements in streams and lakes are prepared and presented in this paper. Effect of toxic elements on the health of the residents in the surrounding residential areas is also discussed.  相似文献