Evaluation of hydrogeochemical parameters and quality assessment of the groundwater in Kottur blocks, Tiruvarur district, Tamilnadu, India

A study was conducted to evaluate the water quality of Kottur block, Thiruvarur district, Tamilnadu. Groundwater samples from hand pumps and tube wells of 16 stations were analyzed during postmonsoon and premonsoon (2008) with the help of standard methods of APHA (1995). Dominance of cations are in the following order Na>Ca>K>Mg and Cl>SO₄>HCO₃>NO₃ by anions in both the seasons. The analytical results shows higher concentration of total dissolved solids, electrical conductivity, sodium, chloride, and sulfate which indicate signs of deterioration but values of pH, calcium, magnesium, and nitrate are within permissible limit as per World Health Organization standards. From the Piper trilinear diagram, it is observed that the majority of groundwater samples are Na-Cl and Ca-Mg-SO₄ facies clearly indicates seawater incursion. In Wilcox diagram, most of the samples fall in low to very high sodium hazard and low to very high salinity hazard indicates moderately suitable for agricultural activities. Kelly’s ratio and magnesium ratio indicates most of the samples fall in suitable for irrigation purpose.     

Early Cenozoic rapid flight enigma of the Indian subcontinent resolved: Roles of topographic top loading and subcrustal erosion

Intrinsic magmatic processes are considered as critical operators of plate movements. Here we demonstrate the role of extrinsic processes consequent to intrinsic processes as a catalyst for anomalous rapid plate movement. The rapid and accelerated flight of the Indian subcontinent since Deccan volcanism until its collision with Eurasia remains as one of the geological conundrums. Data on seismic tomography, peninsular geomorphology and inferences on continuum of subcrustal structures are utilized to address this enigma. We propose geomorphic isostasy as the mechanism that has driven this fastest drift ever recorded in geological history. It was initiated by sudden instability after the Deccan volcanism and resultant extensive accumulation of lava pile over continental lithosphere of northern India, northern-eastern tilt due to crustal thickness heterogeneity and subcrustal thermal stratification. The drift was sustained by Carlsberg and Central Indian ridge-push until collision and sediment top loading at northeast thenceforth. These inferences and geomorphic isostasy as a catalytic mechanism necessitate variability of drift rates as integral inputs for any continental scale modeling.     

Determination of linear polarization and faraday rotation of pulsar signals from spectral intensity modulation

Most of the known pulsars are sources of highly linearly polarized radiation. Faraday rotation in the intervening medium rotates the plane of the linear polarization as the signals propagate through the medium. The Rotation Measure (RM), which quantifies the amount of such rotation as a function of wavelength, is useful in studying the properties of the medium and in recovering the intrinsic polarization characteristics of the pulsar signal. Conventional methods for polarization measurements use telescopes equipped with dual orthogonally polarized feeds that allow estimation of all 4 Stokes parameters. Some telescopes (such as the Ooty Radio Telescope) that offer high sensitivity for pulsar observations may however be receptive to only a single linear polarization. In such a case, the apparent spectral intensity modulation, resulting from differential Faraday rotation of the linearly polarized signal component within the observing bandwidth, can be exploited to estimate the RM as well as to study the linear polarization properties of the source. In this paper, we present two improved procedures by which these observables can be estimated reliably from the intensity modulation over large bandwidths, particularly at low radio frequencies. We also highlight some other applications where such measurements and procedures would be useful.     

Comparison between petroleum hydrocarbon concentrations and magnetic properties in Chennai coastal sediments,Bay of Bengal,INDIA

Petroleum hydrocarbon concentrations (PHC) of surface sediments along the Chennai coast, India, were measured by UV-Fluorescence (UVF) Spectroscopy and the results are expressed in terms of Chrysene equivalents. The concentration of PHC in sediment varies widely (from 1.88 ppm to 39.76 ppm) as compared to the baseline (1.88 ppm) with higher values obtained in the northern part of the study area. The highest magnetic susceptibility (96.8 × 10⁻⁸ m³kg⁻¹) value was determined from the Chennai harbour area. The magnetic parameters show that the Chennai coastal sediments are dominated by ferrimagnetic minerals. The positive correlation (r² = 0.86; p < 0.05) between petroleum hydrocarbon concentrations and magnetic susceptibility suggests that the magnetic minerals and petroleum hydrocarbons along the Chennai coast are derived from the same sources. Factor analysis shows that the magnetic concentration dependent parameters (χ, χ_ARM and SIRM) covary with the petroleum hydrocarbon concentration, suggesting that large amounts of magnetic minerals originate from anthropogenic activities. It is evident that using magnetic measurements may be considered a simple, rapid, cheap and non-destructive method to determine petroleum hydrocarbon concentrations in coastal sediments. Furthermore, this technique may be applied to petroleum exploration studies. Magnetic susceptibility measurements in sediments have been proposed as complementary or alternative means of exploration and assessment of hydrocarbon reservoirs.     

Heavy metal distribution in surface sediments of the Tirumalairajan river estuary and the surrounding coastal area, east coast of India

Surface sediments collected at the Tirumalairajan river estuary and their surrounding coastal areas were analyzed for the bulk metal concentration. The sediments were collected from post- and premonsoon seasons. Dominances of heavy metals are in the following order: Fe > Mn > Zn > Pb > Cu in both seasons from estuary and coastal area. The results reveal that Fe, Mn, Cu, Pb, and Zn demonstrated an increased pattern from the estuary when compared to the coastal area. The heavy metal pattern of the sediments of the Tirumalairajan river estuary and its surrounding coastal area offered strong evidence that the coastal area was a major source of heavy metals to the estuarine region. For various metals, the contamination factor and geoaccumulation index (I _geo) have been calculated to assess the degree of pollution in sediments. The contamination factor and geoaccumulation index show that Zn, Pb, and Cu unpolluted to moderately pollute the sediments in estuarine part. This study shows the major sources of metal contamination in catchment and anthropogenic ones, such as agriculture runoff, discharge of industrial wastewater, and municipal sewage through the estuary and adjoining coastal area.     

Real-time signal processor for pulsar studies

This paper describes the design, tests and preliminary results of a real-time parallel signal processor built to aid a wide variety of pulsar observations. The signal processor reduces the distortions caused by the effects of dispersion, Faraday rotation, doppler acceleration and parallactic angle variations, at a sustained data rate of 32 Msamples/sec. It also folds the pulses coherently over the period and integrates adjacent samples in time and frequency to enhance the signal-to-noise ratio. The resulting data are recorded for further off-line analysis of the characteristics of pulsars and the intervening medium. The signal processing for analysis of pulsar signals is quite complex, imposing the need for a high computational throughput, typically of the order of a Giga operations per second (GOPS). Conventionally, the high computational demand restricts the flexibility to handle only a few types of pulsar observations. This instrument is designed to handle a wide variety of Pulsar observations with the Giant Metre Wave Radio Telescope (GMRT), and is flexible enough to be used in many other high-speed, signal processing applications. The technology used includes field-programmable-gate-array(FPGA) based data/code routing interfaces, PC-AT based control, diagnostics and data acquisition, digital signal processor (DSP) chip based parallel processing nodes and C language based control software and DSP-assembly programs for signal processing. The architecture and the software implementation of the parallel processor are fine-tuned to realize about 60 MOPS per DSP node and a multiple-instruction-multiple-data (MIMD) capability.     

Simultaneous observations of SAO and QBO in winds, temperature and ozone in the tropical middle atmosphere over Thumba (8.5��N, 77��E)

Owing to the importance of middle atmosphere, recently, a Middle Atmospheric Dynamics (MIDAS) program was carried out during the period 2002?C2007 at Thumba (8.5°N, 77°E). The measurements under this program, involving regular radiosonde/rocket flights as well as atmospheric radars, provided long period observations of winds and temperature in the middle atmospheric region from which waves and oscillations as well as their forcing mechanisms particularly in the low-latitude middle atmosphere could be analyzed. However, a detailed analysis of the forcing mechanisms remains incomplete due to the lack of important measurements like ozone which is a significant contributor to atmospheric dynamics. Presently, profiles of ozone are available from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broad Emission Radiometry) satellite globally from about 15 to 100?km, over multiple years since 2002. In this regard, a comprehensive study has been carried out on ozone and its variability at Quasi Biennial Oscillation (QBO) and Semiannual Oscillation (SAO) scales using TIMED/SABER ozone observations during the MIDAS campaign period. Before using the TIMED/SABER ozone measurements, an inter-comparison has been carried out with in situ measurements of ozone obtained under the Southern Hemisphere Additional Ozonesondes (SHADOZ) campaign for the year 2007 at few stations. The inter-comparison showed very good agreement between SABER and ozonesonde derived ozone profiles. After validating the SABER observations, ozone profiles are used extensively to study the QBO and SAO along with temperature and winds in the 20?C100?km height region. It is known that the SAO in mesosphere and stratosphere are in opposite phases, but the present study for the first time reports the aspect of opposite phases in the mesosphere itself. Thus, the present work attempts to study the long-period oscillations in stratosphere and mesosphere in ozone, temperature and winds simultaneously for the first time over this latitude. These observations provided a unique opportunity to explore long-period oscillations in chemistry, dynamics and thermal structure of the middle atmosphere simultaneously.     

Morphological characteristics of Tirumalairajan river, East Coast of India—a GIS approach

Morphological mapping plays an essential role in understanding river processes. Evaluation of the morphological parameters requires preparation of basin, upstream and downstream, stream link, stream network, stream order, flow direction, flow accumulation, and digital elevation model, which help to understand the nature of the river. Assessments of morphological digital maps provide upstream and downstream flow rates, slope variation, sedimentation, and specific stream erosive power in river systems. The river patterns of the study area mainly controlled by geological nature. Therefore, this paper discusses conceptual foundations and illustrates how mapping approaches can be used to produce morphological information of Tirumalairajan river systems.     

Distribution of grain size, clay mineralogy and organic matter of surface sediments from Tirumalairajanar Estuary, Tamilnadu, east coast of India

The aim of this study is to understand the various sources and factors controlling the abundance and distribution of clay minerals, sand, silt, clay and organic matter of the surface sediments of Tirumalairajanar Estuary in two different seasons. The study was undertaken for two seasons, based on ten selected stations all along the estuary, mouth and freshwater zone. Furthermore, along the estuary region, clay and silt were observed and also at few stations in the upstream end. Organic matters in the sediments appeared to be the main mechanisms for the distribution of clay minerals in estuary indicated that the distributions of clay minerals were comparatively higher during postmonsoon than in premonsoon season. The clay mineral assemblage consists mainly of chlorite, kaolinite, montmorillonite, illite and very scarce gibbsite. The clay from the sediments has been separated and studied for mineral identification using X-ray diffraction analysis. The present study also reveals that sediment texture is one of the main controlling factors for the distribution of organic matter.     

Barium anomaly preceding K/T boundary: possible causes and implications on end Cretaceous events of K/T sections in Cauvery basin (India), Israel, NE-Mexico and Guatemala

Maastrichtian–Danian strata of the Cauvery basin as well as selected sections of NE-Mexico, Guatemala and Israel record Ba anomalies, away from the Cretaceous/Tertiary boundary (KTB) in addition to common occurrences of geochemical and stable isotopic anomalies across the KTB. Ba anomalies were recorded in monotonous shallow marine sandstones of the Cauvery basin (south India) which contain minor amounts of Ba-orthoclase. Barium anomalies were observed also in shallow marine carbonates in sections of Israel, NE-Mexico and Guatemala. Calculation of excess Ba with reference to PAAS (Post-Archaen Average Australian Shale), comparison of coeval geochemical anomalies, depositional pattern and associated petrographic and mineralogical features of the Cauvery basin revealed that while a first Ba peak was related to detrital influx, the second Ba peak was coincident with sea level fall which in turn may have been influenced by emission of volatile hydrocarbons and resultant climatic changes. In view of intrinsic involvement of Ba in various geochemical processes and occurrence of Ba anomalies in K/T sites distributed around the world (NE-Mexico, Guatemala and Israel), it is suggested that probable causes of such widespread Ba-anomalies should be taken into consideration while analyzing end Cretaceous events. These observations support the views espoused by many workers who have stated that the K/T boundary was also accompanied by many non-catastrophic events that might have contributed to environmental stress on marine fauna, as a result of which selective multi-stage extinctions occurred.