Multivariate statistical approach to identify significant sources influencing the physico-chemical variables in Aerial Bay,North Andaman,India

Aerial Bay is one of the harbor towns of Andaman and Nicobar Islands, the union territory of India. Nevertheless, it is least studied marine environment, particularly for physico-chemical assessment. Therefore, to evaluate the annual spatiotemporal variations of physico-chemical parameters, seawater samples collected from 20 sampling stations covering three seasons were analyzed. Multivariate statistics is applied to the investigated data in an attempt to understand the causes of variation in physico-chemical parameters. Cluster analysis distinguished mangrove and open sea stations from other areas by considering distinctive physico-chemical characteristics. Factor analysis revealed 79.5% of total variance in physico-chemical parameters. Strong loading included transparency, TSS, DO, BOD, salinity, nitrate, nitrite, inorganic phosphate, total phosphorus and silicate. In addition, box-whisker plots and Geographical Information System based land use data further facilitated and supported multivariate results.     

Numerical groundwater-flow modeling to evaluate potential effects of pumping and recharge: implications for sustainable groundwater management in the Mahanadi delta region,India

Process-based groundwater models are useful to understand complex aquifer systems and make predictions about their response to hydrological changes. A conceptual model for evaluating responses to environmental changes is presented, considering the hydrogeologic framework, flow processes, aquifer hydraulic properties, boundary conditions, and sources and sinks of the groundwater system. Based on this conceptual model, a quasi-three-dimensional transient groundwater flow model was designed using MODFLOW to simulate the groundwater system of Mahanadi River delta, eastern India. The model was constructed in the context of an upper unconfined aquifer and lower confined aquifer, separated by an aquitard. Hydraulic heads of 13 shallow wells and 11 deep wells were used to calibrate transient groundwater conditions during 1997–2006, followed by validation (2007–2011). The aquifer and aquitard hydraulic properties were obtained by pumping tests and were calibrated along with the rainfall recharge. The statistical and graphical performance indicators suggested a reasonably good simulation of groundwater flow over the study area. Sensitivity analysis revealed that groundwater level is most sensitive to the hydraulic conductivities of both the aquifers, followed by vertical hydraulic conductivity of the confining layer. The calibrated model was then employed to explore groundwater-flow dynamics in response to changes in pumping and recharge conditions. The simulation results indicate that pumping has a substantial effect on the confined aquifer flow regime as compared to the unconfined aquifer. The results and insights from this study have important implications for other regional groundwater modeling studies, especially in multi-layered aquifer systems.     

Passive microwave remote sensing contribution to hydrological variables

Physical principles governing passive microwave remote sensing of hydrological variables are outlined and illustrated by actual observations by ground-based, air-borne and space-borne microwave radiometers operating at different frequencies. Specific hydrological variables addressed in this paper are soil moisture, seasonal inundation of rivers and swamps, vegetation, snow, and rainfall. Passive remote sensing provides measurements of electromagnetic radiation emitted by the land-atmosphere system, which can be related more directly to the radiative characteristics of the system than to physical or physiological characteristics. Estimation of hydrological variables from microwave observations necessarily involves models relating the radiative to the physical characteristics, and in general more than one physical characteristics determine the microwave observations. This non-uniqueness in the relationship between microwave observations to a particular hydrological variable leads to uncertainties in the estimation of the variable. Notwithstanding this limitation, the principles and the examples given in this paper illustrate the value of passive microwave observations to regional and global hydrology at a temporal resolution of days aggregated to a decade.     

Electro-flotation of chalcopyrite fines

Electro-flotation tests were conducted on chalcopyrite particles with a modified Hallimond tube designed for electro-flotation, using platinum anode—copper cathode and graphite anode—copper cathode systems. Flotation tests were carried out for fines of chalcopyrite of size below 20 microns with potassium ethylxanthate as collector. Studies were done on flotation with hydrogen and oxygen separately with the usual variables. Dissolution of chalcopyrite at various current densities, with reagent at optimum conditions and without reagent was also studied. It is observed that electro-flotation particularly with oxygen, is effective in the flotation of fine particles of chalcopyrite.     

Microwave response of green vegetation

The cavity perturbation technique has been used to measure the dielectric constant of vegetation, such as soyabean, grass, corn and green spruce at 9.5 GHz. The dielectric properties of these vegetations are highly dependent upon the moisture content. For freshly plucked specimen the dielectric constant was found to be maximum which decreased gradually as the specimen dried up. The role of these basic physical parameters in microwave scatterometer experiment has been discussed. Some parameters of remote sensing application have been estimated from these measurements and their practical role has been discussed     

Model tank experiments for resistivity measurements on non-conducting and conducting sheets

Summary Model tank experiments for conducting and non-conducting sheets have been described and the results compared with those of other workers.     

Studies in the dielectric constant of Indian sandstones as a function of water content,part II

Summary Dielectric constants of many sedimentary and metamorphic rocks as a function of water content and frequency have been measured and represented graphically. The results are discussed in the light of known theories. The most significant part of the observations is a type of hysteresis cycle in the values of the dielectric constant for increasing and decreasing water content.     

Magnetic survey over Jharia Coal Field

Summary Magnetic survey over Jharia Coal Field has been conducted using Askania torsion magnetometer. Nearly 200 observations were taken over the sedimentary outcrops as well as over crystalline rocks surrounding these. The anomaly map was prepared. The map shows interesting correlation with tectonics of the basin and throws some light on the nature of the underlying basement.     

Note on Parasnis' method for surface rock densities

Summary Assuming a zero regional, Parasnis presented a linear relationship between the relative gravity and the average surface rock density. If a certain amount of regional variation in the relative gravity exists this method cannot be relied upon. In the present article an extension of Parasnis' method is suggested for the case when linear regional exists. A field example from the Godavari Valley is described.