Sea surface temperature variability over North Indian Ocean — A study of two contrasting monsoon seasons

Using the satellite derived sea surface temperature (SST) data for 1979 (bad monsoon) and 1983 (good monsoon), the SST variability for two contrasting monsoon seasons is studied. The study indicates that large negative anomalies off the Somali and Arabian coasts are associated with good monsoon rainfall over India. The strong monsoonal cooling in these regions can be attributed to strong low level winds and intense upwelling. The reappearance of 27°C isotherm off Somali coast in May/June coincides with the onset of southwest monsoon over India. Further, the influence of zonal anomaly of SST off Somalia Coast (SCZASST) and Central Indian Ocean Zonal Anomaly of SST (CIOZASST) with monsoon rainfall over India is brought out. The former is negatively related to the monsoon rainfall over western and central parts of India, whilst CIOZASST is positively related.     

Observed variations of σθ and σΦ in the nocturnal drainage flow in a deep valley

The variations of and in the drainage flow in the Brush Creek valley of western Colorado are investigated using data from Doppler acoustic sodars and instrumented towers. The data were obtained on two experimental nights during the 1984 ASCOT field study. There is good agreement between the variations derived from low-level observations of the sodars and those derived from the towers located throughout the valley. The observed hourly average and in the nocturnal drainage flow are about 20 ° to 25 ° and 5 °, respectively; these values are much larger than those generally observed over flat terrain during nighttime stable conditions. After sunrise (about 0600 MST), as the valley warms and the flow direction changes to up-valley, these parameters increase sharply to their peak values at about 0800 MST and then decrease to their normal daytime values after about two hours.In the drainage flow, the hourly average varies inversely with wind speed according to the relation u 0.7ms^-1. The vertical standard deviation is much less enhanced by complex terrain than the horizontal standard deviation. The observed values are predicted fairly well by the local similarity theory.Oak Ridge Associated Universities (ORAU) Summer Research Participant at ATDD in 1987 andOak Ridge Associated Universities (ORAU) Summer Research Participant at ATDD in 1987 and     

Heavy metal contamination in sediments of Balanagar industrial area,Hyderabad, Andra Pradesh,India

Environmental geochemical studies were carried out to find out the extent of contamination in sediments due to heavy metals in Balanagar industrial area, Hyderabad, Andhra Pradesh, India. The industrial area consisting of 350 small and large industries manufacturing battery, steel planting, pharmaceutical chemicals, metal plating, etc. The present study was undertaken on sediment contamination in Balanagar industrial area, to determine extent and distribution of heavy metals (Cu, Cr, Ni, Pb, Zn, As) and to delineate the source. There is no treatment plant in the industrial area, and many industries release the effluents into nearby nalas and lakes. Solid waste from the industries is also being dumped along the roads and near the open grounds due to which heavy metals migrate from solid waste to the groundwater. The sediments samples were collected from the study area in clean polythene covers and were analyzed for their heavy metals by X-ray fluorescence spectrometry. The concentration ranges of different heavy metals were Cr, 96.2–439.6 mg/kg; Cu, 95.7–810 mg/kg; Ni, 32.3–13,068.2 mg/kg; Pb, 59.2–512 mg/kg; Zn, 157.1–4,630.5 mg/kg; Co, 1.8–48.3 mg/kg; and V, 35.2–308.5 mg/kg. High concentration of heavy metals in sediments can be attributed to some pharmaceutical and metal industries in the study area. Based on the results obtained, suitable remedial measures can be adopted such as phytoremediation and bio-remediation for reduction of heavy metals in sediments.     

Geomagnetic activity control on VHF scintillations over an Indian low latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip)

Using the data of amplitude scintillations recorded at 244 MHz from the geostationary satellite, FLEETSAT (73‡E) at a low latitude station, Waltair (17.7‡N, 83.3‡E, 20‡N dip), during the increasing sunspot activity period of 1997–2000, the effect of the geomagnetic storms on the occurrence of ionospheric scintillations has been studied. A total of 60 SC storms studied during this period, following the Aarons’ criterion, reveals that the local time of onset of the recovery phase of the geomagnetic storms play an important role in the generation or inhibition of the ionospheric irregularities. Out of the 60 storms studied, nearly 60 to 70% satisfied the categories I, II and III of Aarons’ criteria. However, in the remaining 30 to 40% of the cases, no consistent results were observed. Thus, there is a necessity for further investigation of the effect of geomagnetic storms on ionospheric irregularities, particularly with reference to the altitude variations of the F-layer (h’F) relating to the changes in the local electric fields.     

Characterization of channel planform features and sinuosity indices in parts of Yamuna River flood plain using remote sensing and GIS techniques

River planform features and sinuosity are widely acknowledged as important geomorphological indices that control the channel hydraulics and stream power which determines the flow velocity and sediment supply to downstream reaches. Despite their significance, there has been little study about these indices in mighty Yamuna River for understanding the topographic control and hydraulic regime. This paper investigates the channel planform features and sinuosity by employing topographic map, digital elevation model (DEM), and satellite imageries to elucidate the morphological, sedimentological, and hydrological characteristics of the channel. Based on sinuosity index (varies between 1.02 and 1.41), the river segments are categorized into straight (segments 1, 3, 4, 5, 6), sinuous (segments 2, 7, 8, 9, and 11), and meandering (segment 10). The parameters analyzed to find out the influencing factors on sinuosity indicate geomorphological and anthropologic control in their development. Tectonic control of sinuosity in the studied stretch is ruled out as it is flowing through an alluvial plain with low rate of discharge.     

B. P. Radhakrishna – A Lone Crusader

Pyrite containing appreciable content of cobalt (up to 5.61 wt%) and minor amounts of nickel (up to 0.70 wt%) is being reported from electron microprobe studies in a lamprophyre dyke from the Sidhi complex, Mahakoshal belt, Central India. However, cobalt and nickel are conspicuously absent from the associated chalcopyrite reflecting that in a pyrite-chalcopyrite association these elements are preferentially sequestered in pyrite. The microprobe analysis of pyrite grains reveal that their Fe content is variable (40.62 to 46.02 wt%) and reciprocally related to cobalt and nickel concentrations implying the presence of latter as solid solution in the structure of pyrite. The cobalt contents of the pyrite are comparable to those (up to 3.21 wt%) reported from the cobaltbearing pyrites of the Kalyadi copper deposits of Dharwar craton of southern India. Co:Ni (16.05 average) in the studied pyrite appears to be more consistent with a magmatic, rather than a hydrothermal, origin. However, further studies are in progess. This study highlights that besides gold and diamond, lamprophyres are also important carriers of cobalt when available in the magmatic system.     

叠合盆地深层构造—热演化研究方法:以四川盆地为例

与简单盆地和叠合盆地中-浅层相比,叠合盆地深层往往缺乏镜质体反射率等传统古温标,海相碳酸盐岩层次往往缺乏磷灰石、锆石等重矿物而无法开展裂变径迹和（U-Th）/He分析,而且经历了多期复杂热史,古温标早期热记录被后期构造-热事件叠加改造,因此单一古温标和单一的热史恢复模式难以满足叠合盆地深层构造-热演化研究。本文从沉积盆地构造-热演化基本研究方法入手,着重介绍了发展迅速的多种显微组分荧光分析（FAMM）和二元同位素技术。针对叠合盆地深层多期复杂热史恢复的难点,以四川盆地为例总结了开展叠合盆地深层构造-热演化研究的思路和工作方法。叠合盆地深层构造-热演化研究应坚持今古地温场并举、盆地热演化与区域构造演化相结合、地质-地球物理-地球化学三位一体的总体工作思路,多温标耦合,正、反演结合,既考虑岩石圈热演化的动力学规律,又考虑该演化过程对盆地基底沉降、地层发育、古温标热演化程度的影响,只有这样才能保证叠合盆地深层构造-热演化研究结果的可靠性。     

Spatial and seasonal variation of potential toxic elements in Adocia pigmentifera,seawater and sediment from Rameswaram,southeast coast of India

The concentrations of potential toxic elements (PTEs) such as cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) were measured in five different stations of Rameswaram (RM) coast, Gulf of Mannar (GoM), India, in coastal waters in sediments and tissues of Adocia pigmentifera. Concentration of PTEs (Cd, Cu, Pb and Zn) was found to be highest in sediments followed by A. pigmentifera and seawater samples collected from the different stations of RM coast. The pattern of accumulation of PTEs in the three sample types is of the following order Zn < Pb < Cu < Cd. The seasonal variation of these PTEs also followed the same pattern. One-way analysis of variance (ANOVA) with Tukey’s HSD post hoc test has revealed significant differences among stations S1–S4 when compared with the station S5 which is considered as the reference site. Correlation coefficient study showed no significant correlation in the concentration of PTEs in A. pigmentifera, seawater and sediment samples. The concentration of all the PTEs in different sample types has exceeded the FAO/WHO/sediment background values, except for the concentration of Zn in A. pigmentifera and sediment sample, which did not exceed the limits. The contamination factor (CF) and geoaccumulation index (I _geo) values indicated significant contamination of PTEs in the sediments from different stations of RM coast, India. Variations found between the sample types during the studies could be due to changes in levels of pollution discharge over time, availability of PTEs for adsorption as well as variations in the sampling season. Increasing urban sprawl and release of effluents both from domestic and industrial sources are the main sources of pollution at RM coast and are the prime reasons for the loss of existing diverse ecosystem.     

Assessing grade domain of iron ore deposit using geostatistical modelling: A case study

Conventional methods of ore deposit estimates are time consuming, whereas geostatistical methods provide quick and reliable estimates with minimum variance. Geostatistical tools, semi-variograms and kriging, have been used for estimation of grades of an iron ore deposit in the present study. In order to model the deposit and estimate grade, 4537 samples collected from 93 boreholes were used in the study. 3-D data have been converted to 2-D for analyzing the variation of Fe within the boreholes. For each borehole, the weighted mean of Fe grade and its coefficient of variation (CV) are calculated and further analysis is carried out for these two variables. Semi-variogram model suggests that the deposit extends over a zone of influence up to 700 m. Grade maps of kriged estimates reveal that the iron ore deposit is distributed in three distinct zones.