Major ion chemistry and identification of hydrogeochemical processes controlling groundwater in and around Neyveli Lignite Mines, Tamil Nadu, South India

Groundwater geochemistry was studied in and around the Neyveli lignite mining region of Tamil Nadu, India. Representative groundwater samples (168) were collected from bore wells during June 2004, October 2004, January 2005, and March 2005 to broadly cover seasonal variation. Higher electrical conductivity values were observed in the southeastern and southwestern part of the study area. During the southwest monsoon (June) and postmonsoon (January) seasons, bicarbonate?+?chloride dominated the anions, with few representations for sulphate. Sodium?+?potassium were the dominant cations in all the seasons except in summer (March). The data reveals that the region is a complex hydrogeochemical system with proportional interplay of ions from leaching of ions, ion exchange, agricultural return flow, and stagnant waters. The influence of mine waters and weathering of minerals varies according to the season and spatial distribution of the sources. The water quality can be used for drinking and irrigation, except in a few locations.     

A study on the status of fluoride ion in groundwater of coastal hard rock aquifers of south India

India has an increasing incidence of fluorosis, dental and skeletal, with nearly about 62 million people at risk. High fluoride groundwaters are present especially in the hard rock areas of the country. This paper analyzes the most extensive database on fluoride and other chemical constituent distribution in the coastal hard rock aquifers of Thoothukudi district. A total of 135 samples were collected and analyzed for major cations and anions to assess the geochemical process. The fluoride concentration in drinking waters varied from BDL to 3.2 mg?l^?1 in the study area. Majority of the samples do not comply with WHO standards for most of the water quality parameters. The saturation index of fluorite saturation index was used to correlate with F^? to identify their relationship to increase of fluoride levels. The correlation between the F^? concentration and the water type was also attempted. Spatial distribution of fluoride in groundwater was studied to understand the influencing factors. The relationship of F^? with HCO^? _3, Na⁺ and pH concentrations were studied and found that HCO^? ₃, has good correlation with F^? than the other parameters.     

Interaction Between Two CMEs During 14 – 15 February 2011 and Their Unusual Radio Signature

We report a detailed analysis of an interaction between two coronal mass ejections (CMEs) that were observed on 14?–?15 February 2011 and the corresponding radio enhancement, which was similar to the “CME cannibalism” reported by Gopalswamy et al. (Astrophys. J. 548, L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km?s^?1 in the Solar and Heliospheric Observatory (SOHO)/Large Angle Spectrometric Coronagraph (LASCO), was more than as twice as fast as the slow CME preceding it (326 km?s^?1), which indicates that the two CMEs interacted. A radio-enhancement signature (in the frequency range 1 MHz?–?400 kHz) due to the CME interaction was analyzed and interpreted using the CME data from LASCO and from the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data from Wind/Radio and Plasma Wave Experiment (WAVES), and employing known electron-density models and kinematic modeling. The following results are obtained: i) The CME interaction occurred around 05:00?–?10:00 UT in a height range 20?–?25 R_⊙. An unusual radio signature is observed during the time of interaction in the Wind/WAVES dynamic radio spectrum. ii) The enhancement duration shows that the interaction segment might be wider than 5 R_⊙. iii) The shock height estimated using density models for the radio enhancement region is 10?–?30 R_⊙. iv) Using kinematic modeling and assuming a completely inelastic collision, the decrease of kinetic energy based on speeds from LASCO data is determined to be 0.77×10²³ J, and 3.67×10²³ J if speeds from STEREO data are considered. vi) The acceleration, momentum, and force are found to be a=?168 m?s^?2, I=6.1×10¹⁸ kg?m?s^?1, and F=1.7×10¹⁵ N, respectively, using STEREO data.     

Structure and stability of rotating fluid disks around massive objects. II. General relativistic formulation

In this paper we have considered the structure of a thick perfect fluid disk of constant density rotating around a Schwarzschild black hole and its stability under axisymmetric perturbation. The inner edge of such disk cannot lie within 4m. The critical γ_c for neutral stability is found to be much less than 4/3 indicating that the disks are generally stable     

Charged particle motion on and off the equatorial plane of a magnetic star in Rosen's bimetric gravity

In this paper we have studied in detail (numerically) the trajectories of charged particles in a magnetic field (dipolar at infinity) associated with a static star in the framework of Rosen's bimetric theory of gravity. It was found that there do exist potential wells that allow possible trapping of particles in stable orbits both on and off the equatorial plane. A particularly interesting feature that has shown up is the fact that the characteristics of the effective potential wellV _eff depend on the ratio of the magnetic field strength parameter λ, and the angular momentumL of the charged particle. For values lower than a critical (λ/L) _c the potential well lies within the regionr≤2m.     

Plasma disks around compact objects with self-consistent electromagnetic fields

We present a general formalism for discussing the structure and dynamics of plasma disks, around slowly rotating compact objects, having finite viscosity and conductivity. As a test case we consider the situation for the case when the central object is non-rotating and the plasma is with infinite conductivity and show the existence of equilibrium solution for a self-consistent velocity distribution.     

Tidal effects on groundwater dynamics in shallow coastal aquifers—southeast coast of Tamilnadu,India

Tides play a significant role in the coastal environment; the mangroves, back waters, creeks, and the coastal groundwater interface. Tidal range has been calculated by using TIDECAL software. This study attempts to find the relation between water table condition and tides in the shallow coastal aquifers. The study was conducted by selecting 12 open wells along the coast of the southern part of Cuddalore to the northern part of Nagapattinam district of Tamilnadu. Observations were made in situ for water table fluctuation, dissolved oxygen (DO), and electrical conductivity (EC) for 24 h during full moon (FM) and new moon (NM) of every 2 h. The present study shows the relationship between tidal variations with respect to water table fluctuations and helps to understand the behavior of DO and EC. An interpolation technique, inverse distance weighted (IDW) method was used to obtain the spatial distribution map. The temporal and the spatial relationships between water table fluctuation, EC, and DO were also used in order to understand the coastal ecosystem in the natural environment.     

An analysis of beach profile changes subsequent to the Colombo Harbor Expansion Project,Sri Lanka

Man-made coastal structures directly affect sediment balance and sediment dynamics on the surrounding beaches. The Colombo Harbor Expansion Project has created about 5-km-long breakwater nearly perpendicular to the beach. The present study is focused on quantitatively and qualitatively analyzing the effect of the Colombo Harbor Expansion Project on economically important beaches in and around Colombo city area. In this study, the authors measured monthly variations of beach width, beach profile and the mean grain-size of the sediments at mean sea level for complete annual monsoon cycle. Data were analyzed to establish site-specific erosion vulnerability. Monitoring results show that cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). In addition, the cumulative and site-specific sand accretion and erosion patterns have a clear relationship with the monsoon seasonality. Beaches were narrower during the stormy southwestern monsoon, whereas beaches were wider during fair weather of northeast monsoon and inter-monsoon periods. In contrast, the constructed breakwater obstructs natural longshore sediment dynamics. For example, a significant amount of sediments from the Kelani-Ganga River were buried in the Colombo Harbor due to alteration of prominent longshore sediments transportation on the western coast of Sri Lanka. Therefore, this study shows enhancement of coastal erosion in the studied southern beaches due to a lack of sediment deposition.     

Influence of nearshore sediment dynamics on the distribution of heavy mineral placer deposits in Sri Lanka

Beach sediments in Sri Lanka contain industrial-grade heavy mineral occurrences. Samples of both offshore and onshore sediments were collected to examine the provenance, mineralogy and geochemical compositions of the heavy mineral occurrences. Coastal morphodynamic changes along the coastline of Sri Lanka were analyzed using the time-series satellite images. These coastal morphodynamic changes were used to identify the prominent directions of monsoon-influenced longshore currents, coastal sediment accretion and depositional trends and their relationships to the provenance of the heavy minerals. Results show the concentrations of detrital ilmenite, zircon, garnet, monazite, and rutile vary in the onshore and offshore sediments. The heavy mineral potential of the northeastern coast is high (average contents of about 45–50% in the Verugal deposit, 70–85% in the Pulmoddai deposit, and 3.5–5.0% in offshore samples stretching from Nilaveli to Kokkilai), compared to sediments in southwest (average content about 10% in onshore sediments and 2% in offshore sediments from the mouth of the Gin River). Therefore, no economic-grade heavy mineral placers were identified in the offshore environments. The high concentrations of heavy minerals in beach sediments and low concentrations in offshore sediments suggest operation of a panning system in the surf zone to form enriched placer deposits. Major and trace element compositions of beach sediments show marked enrichments of TiO₂, Fe₂O₃, La, Ce, Zr, Cr, Nb, Th and V compared to average Upper Continental Crust (UCC) values. Analysis of prominent coastal longshore transport patterns identifies bidirectional sediment transport in the northeast coast of Sri Lanka. In the southwestern coast, two transport directions occur with anti-clockwise transport from Galle to Hambantota, and clockwise transport from Hikkaduwa to Wadduwa. The heavy minerals in the placers were mainly derived from Precambrian metamorphic rocks, and transported to the coast through the river systems of Sri Lanka.