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A comprehensive measurement of concentrations of the natural radionuclides 238U, 232Th and 40K, and 226Ra in the soil and rocks along with natural uranium and tritium activity levels in lake water were carried out during the Indian expedition to Antarctica. The samples were collected from the Larsemann Hills region in Antarctica (latitude 69°20′ S to 69°25′S, longitude 76°6′ E to 76°23′E). The data on the natural radioactivity for this region is limited. The study was carried out to establish baseline levels of radioactivity in different terrestrial matrices of this region such as soil, rocks, and lake water. A radiation survey mapping for terrestrial radioactivity was conducted in the region before collection of soil and rock samples. The soil and rock samples were analyzed for natural radioactivity concentrations using high-resolution gamma spectroscopy system. The major contributor to elevated gamma radiation background is attributed to the higher concentration of 232Th and 40K radionuclides in both soil and rocks. Terrestrial components of gamma dose rate due to natural radioactivity have been estimated from the measured radioactivity concentrations and dose conversion coefficients. Several "hotspots" and high background areas in the region have been identified having significantly higher concentration of 232Th and 40K. Rocks in Larsemann Hills region showed high reserve of thorium mineralization in monazites and 40K in K-feldspar. The concentrations of 232Th in soil are found to be in the range of 106–603 Bq/kg, whereas in rock it is in the range of 8–4514 Bq/kg. Natural radioactivity U (nat) and 3H contents in the lake water samples in Larsemann Hills region were estimated as 0.4 and 1.3 Bq/L and are well within the prescribed limit of radioactivity in drinking water as recommended by World Health Organization. [ABSTRACT FROM AUTHOR]

Study on the measurement of background radiation level in and around Bharati station, Larsemann Hills region of East Antarctica was taken up using different types of detectors. The radiation levels due to cosmogenic (especially neutron) and terrestrial origin (gamma and neutron) and natural radioactivity due to presence of primordial radionuclide in the samples of soil, rock, lake water, ice and air were measured. The data on radionuclide activities of soil and lake water are presented pictorially using surfer plot. The study was further extended to the in-situ measurement of Radon/Thoron concentration in soil pores. Measurement of gross alpha and beta activity in air samples was also carried out. These studies were conducted during several Indian Scientific Expeditions to Antarctica (ISEA) (32nd to 36th) for the period from 2012 to 2017. Some of the data generated during the above mentioned expeditions are already published previously and hence mentioned very briefly in the text whereas the unpublished data are presented and discussed in this article for the first time. [ABSTRACT FROM AUTHOR]

We present textural evidence of spinel (low-Zn) and quartz from two samples of quartzofeldspathic rocks from the Larsemann Hills, East Antarctica. The present occurrence is unusual for the fact that the direct grain contact is preserved unlike most other occurrences where these two phases are separated by reaction products during retrograde and/or prograde metamorphic stages. Textural features further indicate that Ti-biotite was part of the prograde assemblage that underwent partial melting to produce spinel. The maximum temperature estimated from the rock is 870 °C. Monazite grains are abundant in the rock and these are mostly homogeneous in terms of U, Th and Pb distribution. In situ U–Th-total Pb EPMA data of these monazite yield a group age of 527 ± 8 Ma. Textural and geochronological data match with the second (M 2) stage of metamorphism of the Larsemann Hills region as evident from the existing geological record. Although spinel and quartz was considered to be a part of peak M 2 assemblage in earlier studies, preservation of their grain contact is enigmatic. We consider the grain contact metastable and its preservation possibly resulted from significant overstepping of cooling reaction due to fast reaction kinetics. [ABSTRACT FROM AUTHOR]

Tissue equivalent proportional counter (TEPC) model HAWK FWAD-3 was used for the evaluation of absorbed dose, dose equivalent rate (Ḣ TEPC) and microdosimetric spectra measured (i) in the mixed radiation fields formed mainly by cosmic rays onboard aircraft during the flights between Mumbai and the Indian station Bharati (Progress air base), two polar flights at Antarctica, and (ii)ground level environmental radiation field at locations situated in three continents, namely Antarctica, Africa and Asia with different latitudes. The study also includes evaluation of absorbed dose rate, dose equivalent rate of cosmic rays and terrestrial radiation using active detectors namely RADEYE-G and BERTHOLD Rem counter. An effort was made to compare the measured dose equivalent rate by TEPC for the commercial flight routes to Antarctica with the values calculated by the software code EPCARD and a good agreement was observed. The 35th expedition to Bharati, Antarctica showed higher values of dose equivalent at the pole (Larsemann Hills region, 69°24′37.60″S, 76°11′01.70″E) than the world average for an evaluation period of six months during summer. • TEPC used for the measurement of absorbed dose, Ḣ TEPC and microdosimetric spectra for the flight routes. • Measurement of absorbed dose, Ḣ TEPC and microdosimetric spectra at locations of three continents including Antarctica. • Analysis of low and high LET components of cosmic ray to absorbed dose at different altitudes. • Comparison of the measured flight route doses were made with the calculated values by the software code EPCARD. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of quartz samples extracted from soil of Fisher Island (76° 13ʹ 23.9ʺ E, 69° 23ʹ 31.9ʺ S) in Antarctica were studied. The nature of signals indicated presence of a dominant slow component in the OSL signal. The widely utilized Single Aliquot Regenerative (SAR) protocol for dose recovery was found unsuitable for this particular sample due to the dominating slow component in the OSL signal. Efforts to minimize the effect of slow component in dose recovery by adopting procedures like, bleaching with blue light, and early background subtraction were carried out. Additionally, thermally transferred OSL (TT-OSL) studies were conducted on the natural sample and dose estimation using the TT-OSL SAR protocol was carried out. • TL/OSL properties of quartz extracted from sediments collected from Fisher Island, Antarctica. • OSL dating using SAR protocol. • Thermal transferred OSL SAR protocol. • Limitations of using quartz extracted from Antarctica sediments for OSL dating. [ABSTRACT FROM AUTHOR]

In the present study, thoron exhalation flux density were measured in the soil samples collected around the Indian station namely Bharati (69° 24.41′ S, 76° 11.72′ E) and its nearby islands in the Larsemann hills region of Antarctica. Further, dependency of thoron mass emanation rate and emanation coefficient on the soil grain size was studied by segregating the soil samples into four different grain size groups: 50–100 μm, 100–200 μm, 200–500 μm and 500–1000 μm which showed that both of them follow a decreasing trend with increase in grain size. A comparison of measured mass emanation rate between different soil samples showed that it had a larger variation for the smaller grain size which eventually decreased as grain size increased while emanation coefficient was observed to be nearly constant for all the grain size groups. The variation in emanation coefficient with respect to mean grain size has been investigated and an empirical exponential model has been proposed for predicting emanation coefficient for different grain sizes. • Thoron exhalation from soil samples of Antarctica has been investigated. • Effect of grain size on thoron emanation and exhalation has been studied. • An empirical relation is proposed to estimate emanation coefficient from grain diameter. [ABSTRACT FROM AUTHOR]