Magnetic susceptibility and radiological hazardous nature of the river sediments - Spectroscopical approach

Abstract

Magnetic susceptibility, radioactivity and mineralogical characterization are performed on 40 sediment samples collected from the Ponnaiyar river, Tamilnadu, to establish a possible link between the enhanced concentration of anthropogenic magnetic particles, radionuclides and minerals. Higher magnetic susceptibility values (> 150 x 10-8 m3/kg) are observed in last 100 km of the river. However, some elevated values are also observed in first 100 km. Frequency dependence of magnetic susceptibility is calculated to understand the magnetic grain variations which are presented and discussed. The average activity concentration of radionuclides (238U, 232Th and 40K) falls within the typical world and Indian average values although some extreme values are determined. To assess the radiological hazard of river sediments, radiological hazard indices such as absorbed dose rate, annual effective dose equivalent, radium equivalent, hazard indices (Hex, Hin, Iγ, I and excess lifetime cancer risk) are calculated which shows below the internationally recommended values. The relative distribution of major minerals is determined by calculating extinction coefficient. Correlation analysis is carried out between the parameters obtained from radioactivity analysis and other analyses to know the existing relations. Obtained correlations are discussed and suggest that the natural radioactivity level and magnetic susceptibility of the present sediments is mainly controlled by clay content.