Groundwater pollution due to discharge of industrial effluents in Venkatapuram area, Visakhapatnam, Andhra Pradesh, India

 Hindustan Polymers Limited was established in the Venkatapuram area in the northwestern part of Visakhapatnam urban agglomeration. Untreated industrial effluent from the plant is discharged with total dissolved solids concentrations reaching up to 6500 mg/l. The groundwater pollution was identified as early as 1981 and a hydrogeologic and water-quality database is available from 1981. The groundwater quality in the plant environs is found to be in the range of 3500–4500 mg/l. Major chemical constituents of industrial-waste waters consist of Na, Cl, and SO₄. Some characteristic parameters of the aquifer were estimated. The available hydrogeologic and hydrologic data was analyzed to conceptualize the groundwater regime. A mathematical groundwater flow model was constructed to compute the hydraulic head at the center of finite-difference grid. The computed head distribution and effective porosity of the formations were used to calculate the groundwater flow velocity. The computed velocity field was ultimately used to prognose the pollutant migration in groundwater accounting for the advection and dispersion processes in the mass transport model and for determining the time-dependent pathlines of pollutant. Areal migration of pollutants from the source was predicted up to year 2002. Received: 23 December 1996 · Accepted: 9 September 1997     

Electrical conductivity of some Indian basalts under various temperature conditions

Electrical conductivity of nineteen samples of the Deccan Traps, collected from the Pawagarh area and two boreholes drilled at Koyna, has been measured in the temperature range from 475 K to about 1100 K. The results indicate the change of the conduction mechanism from impurity to electronic/ionic conduction as the temperature increases. Few samples show the normal behaviour, i.e. the increase of conductivity with temperature, while some samples show an anomalous behaviour between the temperatures 600 and 1000 K. This anomalous behavior may be due to either the dehydration of OH^? ions or/and the oxidation of Fe²⁺ to Fe³⁺.     

Shield-like upper mantle velocity structure below the Indo-Gangetic Plains: Inferences drawn from long-period surface wave dispersion studies

Shield-like upper mantle velocity structure has been inferred to exist below the Indo-Gangetic Plains from a study of mantle Rayleigh and Love wave group and phase velocities for periods extending to 200 seconds. The investigations have been carried out for the path between the World Wide Standard Seismic Network Stations at Chiengmai (CHG), Thailand, and New Delhi (NDI), India, for an earthquake with its epicenter in the New Hebrides Islands. Application of improved frequency time analysis has permitted measurement of regional surface wave dispersion for periods extending to several minutes; previous results for this region were for periods no greater than about one minute.     

Teleseismic P-wave residual investigations at Shillong,India

The northeast India region is seismically very active and it has experienced two large earthquakes of magnitude 8.7 during the last eight decades (1897 and 1950). We have analysed teleseismic P-wave residuals at Shillong, the only reliable seismic station operating in the region, to investigate a possible association of travel-time residual anomaly with earthquake occurrence. The period covered is from October 1964 through March 1976. The total number of events is 9479, including 1767 events with depth >/ 100 km. Six-monthly average residuals have been calculated. The standard deviations are less than 0.10 sec for these data sets. During the period of investigations, no major earthquake took place close to Shillong. The earthquake of June 1, 1969 with a magnitude (M_b) of 5.0, at an epicentral distance of 20 km from Shillong is the only significant event. This earthquake is found to be associated with a travel-time increase with a maximum amplitude of 0.4 sec. It appears that, in general, the P-wave velocity has decreased in the neighbourhood of Shillong since 1969. A quadrant-wise analysis of residuals indicates that the residual anomaly is most prominent in the SE quadrant from Shillong.     

The detection and recognition of underground nuclear explosions

This paper reports on a joint meeting of the Royal Astronomical Society's Joint Association for Geophysics and VERTIC (the Verification Technology Information Centre) held in London in 1992. The topics presented focused on the detection and recognition of underground nuclear explosions. The objective of the meeting was to emphasize the multi-methodological approach that is important in verifying compliance with test-ban treaties. An overview of seismological monitoring was followed by a discussion of the technical and scientific aspects of a global seismic monitoring network, and in particular of the 1991 experiment to test the large-scale international exchange of seismic data between recording stations and data centres world-wide. The current capabilities of satellite remote-sensing were presented, and their use explained in terms of both the provision of information for monitoring the development of foreign nuclear testing programmes and also for providing sufficient information for the evaluation of treaty compliance. A review of radio-isotope sampling showed how the isotopic signature of both air and ground based sampling programmes can be diagnostic of the nuclear source. Finally, previously classified research on the ionospheric effects of underground nuclear explosions was presented, the generated acoustic waves disturbing the ionosphere and producing detectable changes in the reflection of radio and radar signals which have potential as a monitoring technique.     

A note on computing uniform risk spectra from intensity data on earthquake occurrences

Reliability of uniform risk Fourier and response spectra, derived from Modified Mercalli Intentsity data, on earthquake occurrences has been investigated by comparing these spectra with the corresponding spectra based on magnitude data. By treating the site intensity from ab earthquake, with given maximum intensity and epicentral distance, as a random variable, a Bayesian probability approach is suggested to compute the intensity spectra, in the present study. Examples of comparison of the intensity and the magnitude spectra for two typical sites in the highly seismic northeast Indian region have shown very good consistency and agreement between the two spectra. Thus, in the proposed approach, intensity data can be used to get quite reliable design spectra for regions where the history of instrumentally recorded data is not sufficient for engineering seismic risk analysis.     

ON ANALYSIS OF STEP-DRAWDOWN DATA

Abstract. A procedure is described for the analysis of step- drawdown pumping test data. The method uses the general form of the drawdown equation during a step with the superposition of the effects of incremental pumping between steps. An interactive computer code based on this procedure is developed to estimate aquifer characteristics and well-loss factor from the observed time-drawdown data at different discharge rates. Analysis of specific step-drawdown data indicates the adaptability of the code for practical application.     

Alterations in the architecture of the gill surface produced by water-borne copper in Heteropneustes fossilis (BLOCH)

In the present investigation the effect of water-borne copper on the gill architecture of a freshwater teleost, Heteropneustes fossilis (BLOCH ) was studied through scanning electron microscopy. The changes produced on the gill surface in a sublethal measured copper concentration (8.17 mg/1) in static bioassay after 96 h of exposure were fusion of secondary lamellae, rupture of various cellular components and deposition of excessive mucus and blood on the gill surface. The epithelial surface of treated gill thus lost the organized structures like microvilli, arborizing ridges and channels. The cause of fish mortality due to action of copper has been discussed in reference to reduced relative diffusing capacity along with other wide ranging effects on the metabolism of fish.