Mineral and magnetic parameters as proxies for natural radioactivity level in Vaigai river sediment: Horizontal and vertical approach

The present study is aimed to show that the mineral and magnetic parameters are proxies for radioactivity level of Vaigai river sediment. In order to show the usefulness of above said parameters as proxies for radioactivity level of the river, elaborate analyses along with radioactivity level need to be analyzed in horizontal (different locations) and vertical (upper, first, second and third feet) views of the river. The radioactivity analysis shows that average concentrations of 238U, 232Th and calculated absorbed dose rate are within the recommended safety level in all depth samples. Eleven minerals have been identified and characterized by FTIR, and are confirmed by XRD techniques. Based on the calculated results of extinction co-efficient, the amount of major minerals are decreased in the order of quartz > microcline feldspar > orthoclase feldspar > kaolinite in all depth samples. The presence of ordered crystalline quartz in all depth samples have been assessed by the calculated crystallinity index values. These observations are matched with XRD results. Magnetic susceptibility measurement was carried out in horizontal and vertical views which show the presence of dia, ferri, antiferri and ferrihydrate magnetic minerals in present sediments. Studied characteristics and their distributions are almost similar in all the depths. Multivariate statistical analyses include cluster analysis (CA), Factor analysis (FA) and Principal component analysis (PCA) are effective tool to show the above said parameters as proxy and the analyses are carried out. Relevant justification is also given for explaining the parameters as proxy. In the clay mineral, high adsorption of radionuclides and magnetic minerals occurs in lattice defects or onto crystal and grain boundaries due to the high cation exchange capacity. Since, the parameters such as content of clay, magnetic susceptibility and amount of kaolinite (clay) in all depth samples are strongly associated with radioactivity variables, one can say that above said parameters may be proxies for determining the level of radioactivity in Vaigai river sediment. •The present study is focused to show the mineral and magnetic parameters as proxies for radioactivity level.•Radiological parameters are within the recommended safety level in all depth samples.•Justification is also given for explaining the parameters as proxy.•High adsorption of radionuclides and magnetic minerals occurs in lattice defects or onto crystal of the