Geochemistry,dissolved elemental flux rates,and dissolution kinetics of lithologies of Alaknanda and Bhagirathi rivers in Himalayas,India

Alaknanda and Bhagirathi (AB) river basins in the Himalayan region in India expose lithologies comprising mainly of granites, low–high-grade metamorphics, shales and carbonates which, in conjunction with the monsoon rains and glacial melt, control water chemistry and dissolved elemental flux rates. In the present study, we monitored two locations: (a) Srinagar on the Alaknanda river and (b) Maneri on the Bhagirathi river for daily variations in total suspended sediments, major ions and dissolved silica over one complete year (July 2004–June 2005). Based on long-term discharge data, discharge-weighted composition and dissolved elemental flux rates (with respect to Ca, Mg, HCO₃, Si) of the river were estimated. The information thus obtained has substantially added up to the existing chemical data of these rivers and has refined the flux rates. Our high-frequency samples provide informations such as (a) water chemical compositions that show a large temporal and spatial variation and (b) carbonate lithology that controls water chemistry predominantly. The dissolution kinetics of various lithologies namely leucogranite, gneiss, quartzite, phyllite and shale of the AB river basins were studied through batch experiments at controlled temperature (25 and 5°C) and pH (8.4) condition. In laboratory, these lithologies undergo slow rates of dissolution (10⁻¹³ to 10⁻¹⁵ mol/m² s), while field weathering rates based on dissolved elemental flux rates in the AB rivers are much higher (10⁻⁸ to 10⁻⁹ mol/m² s). Extremely high physical weathering rates in AB rivers, which enhance chemical weathering significantly, mainly attribute this wide discrepancy in laboratory-derived rates of representative basin rocks and dissolved elemental fluxes in the field. However, laboratory-simulated experiments facilitate to quantify elemental release rates, understand the kinetics of the dissolution reactions, and compare their roles at individual level.     

Complex internal architecture of a debris‐flow deposit revealed using ground‐penetrating radar,Cass, New Zealand

Previous research on debris‐flow deposit structure typically reports little to no visually discernible stratigraphy. The preliminary findings presented here provide evidence for more complex internal deposit architecture with inverse grading and subunits thought to reflect individual flow surges. Ground‐penetrating radar surveys, geospatial data and field observations are used to describe 10 subunits traceable over the 14 lateral radargrams imaging the lower 38 m of the deposit. Additional subunits are depicted further upslope in a longitudinal transect. As well as demonstrating the need for continued investigation of deposit architecture using non‐traditional techniques, these results may help improve future interpretations of post‐event deposits.     

Design of a neuro fuzzy model for image compression in wavelet domain

Image compression forms the backbone for several applications such as storage of images in a database, picture archiving, TV and facsimile transmission, and video conferencing. Compression of images involves taking advantage of the redundancy in the data present within an image. This work evaluates the performance of an image compression system based on fuzzy vector quantization, wavelet-based sub band decomposition and neural network. The vector quantization is often used when high compression ratios are required. The implementation consists of three steps: first, the image is decomposed into a set of sub bands with different resolutions corresponding to different frequency bands. Different quantization and coding schemes are used for different sub bands based on their statistical properties. In the second step, wavelet coefficients corresponding to the lowest frequency band are compressed by differential pulse code modulation (DPCM) and the coefficients corresponding to higher frequency bands are compressed using neural network. Finally, the result of the second step was used as input to fuzzy vector quantizer. Image quality was compared objectively using mean squared error and peak signal to noise ratio along with the visual appearance. The simulation results show clear performance improvement with respect to decoded picture quality when compared with other image compression techniques (Liu, 2005; Premaraju, 1996).     

The lateritic iron ores,itabiritic quartzites and epidiorites of the Kemmangundi area,Bababudan hills,Mysore state,India

Epidiorites forming the basement and occurring also as bands in ferruginous quartzites in Kemmangundi in the Bababudan Hills of Mysore State are described in regard to their structure, mineralogy, petrography, and the petrochemistry of the epidiorites and their role in the formation of the two types of iron ores in the area. The ferruginous quartzites, itabiritic iron ores, and epidiorites strike NW-SE and were simultaneously structurally deformed. They may be considered as eugeosynclinal formations. The data collected do not suggest any genetic relation between the itabiritic ores and the epidiorites. The lateritic iron ores on the other hand, were formed by the alteration of the ferruginous quartzites (itabiritic ores).

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Zusammenfassung Itabiritische Quarzite und Epidiorite aus Kemmangundi in den Bababudan-Hügeln des Staates Mysore wurden hinsichtlich ihrer Struktur, ihres Mineralbestandes und ihrer chemischen Zusammensetzung untersucht. Insbesondere wird der Zusammenhang mit den beiden Typen von Eisenlagerstätten in der Gegend beleuchtet: Die itabiritischen Quarzite haben sich nicht aus den Epidioriten gebildet; dagegen sind die lateritischen Eisenerze als Verwitterungsprodukte der Eisenquarzite zu betrachten.

     

On the complex magnetic behaviour of titanomagnetites

The bulk magnetic properties, including Curie temperature, susceptibility and hysteresis at various temperatures, and the Mössbauer spectra of coarse synthetic members of the titanomagnetite series are compared as a function of titanium content, using some previously reported and some new results. It has been noted previously that the titanium-rich members fail to show the expected “true multidomain” behaviour observed in pure magnetite. One possible explanation is that the behaviour observed may be due to a tendency to inhibit domain wall formation in some titanomagnetites. In this paper we discuss some other possible mechanisms to account for the magnetic properties of such titanomagnetites observable even when domain-wall-related structures do form in them. These mechanisms suggest that magnetocrystalline anisotropy and its temperature dependence in titanomagnetites may be related to local magnetic inhomogeneities, and do not depend only on crystal structure as in the case of classical ferromagnetic materials.     

Satellite-based assessment of physiographic disposition to health problems in kasargod district,Kerala, India

Photo interpretation and digital classification of IRS LISS -III sensor data have been carried out for a few villages affected by abnormal health problems in the Kasargod district of Kerala State. Physical location of the affected villages in relation to the agricultural lands use, watershed characteristics and the extent of cashewnut plantations are studied. It was found that the villages affected by the health problems are located in the microwatersheds that have steep slopes, nearly circular in shape, high runoff potential. The first order streams within these micro-watersheds are originating from the cashewnut plantations that are sprayed with a toxicant called Endosulfan. The study recommends to stop aerial spraying of any toxicant on the cash crops of these watersheds.     

Mapping of hydrogeomorphological features in varaha river basin using IRS data

Hydrogeomorphological mapping in Varaha River Basin (VRB) was carried out to develop relationship between groundwater condition and geomophology of the area. The VRB is located in the north coastal region of Andhra Pradesh is characterised by variability in precipitation, temperature, vegetation, infiltration and run-off. Realising the significance of remote sensing in natural resource management and development, IRS 1A data was used in the study. It is inferred that various hydrogeomorphological units identified in the study area, are the outcome of different geomorphic processes that have been operating in the area and reveal which close relationship between groundwater condition and geology and geomorphol-ogy of the area. Areas covered by buried channels have shallow aquifers of good quality wa-ter with excellent yield. Lineaments and fractures may prove to be potential zones for ground-water development.