V. Ponnusamy

Influence of mineralogical and heavy metal composition on natural radionuclide concentrations in the river sediments.

The natural radiation level has been determined for the sediment samples of the Ponnaiyar River with an aim of evaluating the radiation hazard. The mineralogical characterizations of the sediments have been carried out using the Fourier Transform Infrared (FTIR) spectroscopic technique. The relative distribution of major minerals is determined by calculating extinction coefficient. The concentration and spatial distribution of heavy metals (Pb, Cr, Cu, Zn and Ni) have been studied to understand the heavy metal contamination and its level of toxicity. To evaluate the potential toxicity, heavy metal concentrations are compared with different toxicological and geological reference values. The comparison results suggest that the present metals create an adverse effect on the aquatic ecosystems associated with this river. To assess the sediment contamination due to the studied heavy metals, the Pollution Load Index (PLI) is calculated. Multivariate Statistical analyses (Pearson Correlation, Cluster and Factor analysis) were carried out between the parameters obtained from radioactivity, mineralogical and geochemical analysis to know the existing relations. Obtained results showed that the effect of mineralogy on level of radioactivity should be significant. However, mineralogy effect on heavy metal composition in the sediments should be limited, indicating that other factors such as vicinity of the pollution sources are more important. Also, the influence of mineralogical characterization on level of radioactivity is significant, whereas the influence of the heavy metal composition on level of radioactivity should be limited.

Horizontal and vertical characterization of radionuclides and minerals in river sediments

The natural radionuclide ((238)U, (232)Th and (40)K) contents and mineral characteristics have been analyzed for the different depth sediment samples of Ponnaiyar River with an aim of evaluating the radiation hazard and its relation to specific minerals. To know the complete radiological characteristics, the radiological indices have been calculated and compared with recommended values. In an FTIR study, the extinction coefficient and crystallinity index is calculated to find the relative distribution of major minerals and the crystallinity of quartz, respectively. Both horizontal and vertical distributions of radionuclides and major minerals are studied. Multivariate statistical analyses (cluster and factor) were carried out to determine the relationship between the radioactivity and the minerals. Statistical analyses suggest that the kaolinite is the major mineral to increase the level of radioactivity in the river sediments.

A relationship between the natural radioactivity and mineralogical composition of the Ponnaiyar river sediments, India

The natural radiation level has been determined for the sediment samples of Ponnaiyar River, India with an aim of evaluating the radiation hazard. The average activity concentrations are within the world and Indian average values although some extreme values have been determined. The magnetic susceptibility measurement has been carried out to know the magnetization nature of the sediments. More downstream (mouth) of the river has quite higher magnetic susceptibility values. The mineralogical characterizations of the sediments have been carried out using Fourier Transform Infrared (FTIR) spectroscopic and XRD technique. The minerals such as quartz, microcline feldspar, orthoclase feldspar, kaolinite, calcite, gibbsite, montmorillonite, smectite, palygorskite and organic carbon are identified from FTIR analysis. Few minerals like zircon, monazite and hornblende are identified only in XRD analysis. The relative distribution of major minerals is determined by calculating extinction coefficient. The calculated values show that the amount of quartz is greater than microcline feldspar and very much greater than kaolinite in all the sites. The content of quartz and microcline feldspar is decreases, and kaolinite gradually increases towards the river mouth. Multivariate Statistical analyses were carried out between the parameters obtained from radioactivity analysis and other analyses to know the existing relations. Obtained results are discussed and suggested that the natural radioactivity level of the present sediments is mainly controlled by clay content and lesser extent to magnetic susceptibility.

Investigation on natural radiation level and its hazardous nature of river sediments using γ-ray spectroscopy

The content of natural radionuclides (238U, 232Th, 40K) in sediment samples of Ponnaiyar River, taken from different depths, were determined using a γ-ray spectroscopic system with a NaI(TI) detector with an aim of evaluating the radiation hazard. The results are compared with Indian and world average values. To know the complete radiological characteristics, the radiological indices such as absorbed dose rate, annual effective dose equivalent (indoor and outdoor), radium equivalent activity, hazard index (Hex and Hin), γ-index, activity utilization index, and excess lifetime cancer risk were calculated. The results obtained were discussed and compared with the recommended values. The outdoor γ-dose rates were measured at each sampling site using an environmental radiation dosimeter. The measured results were compared with literature values and correlated with the calculated absorbed dose rate. Averages of all the radiation hazard indices and concentrations of all the measured radionuclides in all the layers are lower than the recommended level. The origin of the detected radionuclides is assessed by comparing the present results with the corresponding values for the earth crust and other rock formations.