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Journal of Radioanalytical and Nuclear Chemistry
Authors:
N. Khare
,
P. Govil
,
Pankaj Kumar
,
A. Mazumder
,
S. Chopra
,
J. Pattanaik
,
S. Balakrishnan
, and
G. Roonwal

Abstract  

The variations in the concentration of 10Be in the core (SK 200/23) from south western Indian Ocean apparently illuminate past levels of 10Be. The level in the core where lower concentration of 10Be (1.01 × 109 atoms/g) is encountered during the Late Holocene is not at tandem with the Late Holocene southern hemisphere temperature variation. The results further suggest that during last glacial maxima (LGM) the 10Be concentration is higher (2.67 × 109 atoms/g) than the Late Holocene values. The present results, though preliminary, show that local bottom topography seems to have influenced the 10Be concentration at core site. Many studies from different geographic regions need to be undertaken before we finally consider 10Be as yet another strong proxy for palaeoclimatic reconstructions.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
R. Dutta
,
M. Sudarshan
,
S. Bhattacharyya
,
V. Vijayan
,
S. Ghosh
,
V. Chakravortty
, and
S. Chintalapudi

Abstract  

Ferromanganese nodules found on the Ocean bed are complex heterogenous mixtures of several components. Two nodules from Central Indian Ocean Basin (CIOB) were analysed by proton induced X-ray emission (PIXE) technique using 3UD Tandem pelletron. The precision and the accuracy of this technique for chemical analyses has been confimed by analysing USGS Geological Standards. Thick sample targets were bombarded by 3 MeV protons for the multielemental analysis. GUPIX-96 software was used for spectral data analysis. Quantative estimate of K, Ca, Tl, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Mo, Ba, Ce, Tl and Pb has been ascertained. The occurrence of Ga, Ge, Rb and Zr in nodules from this region is reported for the first time. The role of manganese and iron oxide phases in determining the uptake of various trace elements from ocean water and bottom sediment pore water has been discussed.

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Abstract  

The iron bearing phases present in a ferromanganese nodule from the Central Indian Ocean have been determined using57Fe Mössbauer spectroscopy. The Mössbauer results have been corroborated by XRD, IR and TG-DTA studies. The Mössbauer spectrum of a ferromanganese nodule shows a broad line width which indicates the presence of more than one iron bearing paramagnetic oxide or oxyhydroxide phases where iron is present as Fe3+. -FeOOH has been distinctly characterised as one of the iron bearing phases in the nodule. Other oxyhydroxide and oxide phases of iron in the nodule have been ruled out. A typical paramagnetic doublet persists even at very high temperature which has been proposed to be due to iron(III)phosphate. Formation of solid solution of Mn2O3–Fe2O3 has been observed in the heat treated nodule at 1073 K, which has been characterised by the Mössbauer technique.

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Abstract  

Three ferromanganese crusts from different locations of the Indian Ocean were analysed by neutron activation analysis using thek 0 method (k 0 NAA method) for studying the distribution of some trace elements along with Fe and Mn. Another crust from the Lau basin of the Pacific Ocean was investigated for comparison of the influence of different oceanic conditions on the trace element distributions in ferromanganese crusts. Variation in Co concentration along with the Mn/Fe ratio were discussed in terms of the hydrogenous/hydrothermal nature of the crusts. The normalised REE content was used to identify possible anomalies. The observed Ce anomaly is discussed in the light of the depositional environment. The precision and accuracy of the method were confirmed by measuring the elemental concentrations in a USGS nodule standard NOD A-1.

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Abstract  

Surface seawater and water vapor about 10 m above the sea level were collected in the Pacific and Indian Oceans during the expedition of KH-96-5 to examine tritium concentrations in open sea. The tritium concentration in the water vapor was one order of magnitude higher than that in the surface seawater, attributed to downward movement of naturally occurring tritium from stratosphere to troposphere.

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Abstract  

The dominant development in the radiometrics techniques for the analysis of short and medium-lived radionuclides in the environment was the utilisation of large volume Ge detectors in underground laboratories with additional anti-cosmic shielding. In the mass spectrometry sector, applications of Accelerator Mass Spectrometry (AMS) and Inductively Coupled Plasma Mass Spectrometry (ICPMS) for the analysis of long-lived radionuclides in the environment are the most important recent achievements. These developments in both sectors did not only considerably decrease the detection limits for several radionuclides (up to several orders of magnitude), but they also enable to decrease sample volumes so that sampling, e.g. of the water column, can be much easier and more effective. Applications of radiometrics and mass spectrometry techniques in isotope oceanography, specifically on the distribution of 3H, 14C, 90Sr, 129I, 137Cs, 239Pu and 240Pu in the water column of the North Pacific and South Indian Oceans are presented and discussed.

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