Radioactivity Levels In Sediments Research Articles

Long-lived radionuclides in marine sediments from the Beibu Gulf, South China Sea: Spatial distribution, controlling factors, and proxy for transport pathway

The source and transport process of sediments are of great concern in marine sedimentology. In this study, naturally occurring radionuclides (238U, 226Ra, 228Ra, and 40K) in surface sediments and sediment cores were comprehensively analysed using high-purity germanium (HPGe) γ spectrometry in order to explore radionuclide fingerprints as novel proxies for tracking the source and transport pathway of sediments in the Beibu Gulf. We found that the radioactivity level of sediments in the Beibu Gulf was lower than that in other Chinese seas, following a comprehensive compilation and comparison of radioactivity in the region, indicating the Beibu Gulf is a high-quality marine environment. An interesting “butterfly pattern” was exhibited in the horizontal distribution of radionuclides in surface sediments from the Beibu Gulf, mainly attributable to the controlling factors of the non-linear negative regulation of sediment grain size and positive role of total organic carbon in sediment. Furthermore, the vertical distribution of radionuclides in sediment cores was affected by the redox state and a physical/biological disturbance, which were demonstrated by the simultaneous analysis of redox-sensitive element Mn and 210Pb, respectively. Additionally, the 226Ra238U endmember model and 232Th238U endmember model were proposed for quantifying local input (85%) and trans-region input (15%) of marine sediments in the Beibu Gulf in the context of the Guangdong-Qiongzhou Strait-Guangxi framework. We inferred that the Beibu Gulf was at risk of contamination by artificial radionuclides derived from nearby Guangdong Province, which has the highest number of nuclear power plants in China, through a trans-region input by ocean currents. Our study not only provided spatiotemporal distributions of radionuclides in the Beibu Gulf and their controlling factors (sediment grain size, total organic carbon, redox state, physical/biological disturbance, and ocean currents) but also indicated the radionuclide fingerprints (226Ra/238U and 232Th/238U) as potential geochemical proxies for quantifying the distinct sources of radionuclides and other associated chemicals (e.g., heavy metals, organic pollutants) in sediments.

Radiometric signature as an indicator of radiological pollution on Rio Doce after the disaster in tailings dam

Doce River suffered major environmental impacts throughout their courses due to the disruption of the tailings dam of the company Samarco—Brazil, characterizing it as the biggest accident in the mineral area throughout the southern hemisphere. The radiometric signature obtained for natural radionuclides of occurrence in sediment is an indicator of radiological pollution caused by accidents. By means of gamma-ray spectrometry, this work determined the radioactivity levels in sediments from samples collected before (2014) and after (2015) the accident obtaining indicators of pollution radiometric, namely radium equivalent, external and internal radiological risk, and compare them with the reference levels.

Natural radioactivity levels in sediments in Algiers Bay using instrumental neutron activation analysis

Abstract The main objective of this study is to evaluate natural radioactivity levels in sediments collected from different points of Algiers bay. Particular attention was paid to understand correlations between the distribution of uranium and thorium and the geomorphological characteristics of the Bay. Instrumental neutron activation analysis (INAA) has been employed in order to measure the isotopic composition and concentration of uranium and thorium, with emphasis on isotopes, 232Th and 238U. The concentrations reported in Bq kg−1 (dry weight) vary between 19.73 and 34.53 for 238U and between 22.26 and 36.02 for 232Th. The obtained results are within the world typical ranges and did not show any anomalous values. Results revealed clear inverse relationship between activity concentration and grain size. The radioactivity content in sediments had a positive correlation with clay and silt percentage, and a negative correlation with sand percentage. The concentration ratios of 232Th/238U are found to be slightly below the world average value unite (3.94) in sediments. Values below unite indicate that the medium is reductor or the existence of an external source of U-contaminated particles in the bay; Values greater than the unit show either depletion of uranium or enrichment of thorium due to alteration or natural processes in these areas. The strong correlation of uranium and Thorium in samples reflects the source of same origin. The results of the study can be used as basic radiometric data for future sedimentological studies. The situation in the Bay of Algiers is reassuring but the risk of possible contamination cannot be excluded and requires constant vigilance for the preservation of the coast and the Mediterranean from all contamination. The results can also be used as reference data for the monitoring of possible radioactive pollution in the future.

Dose estimation and calculation of radiological hazard index at Doce River / Brazil due to Fundão dam rupture

The monitoring of the activity of radionuclides of natural occurrence as 238U, 232Th, 226Ra, 40K including 210Pb is important to assess the radiological impact and human exposure due to radioactivity in estuaries. In the case of the Doce River, a mining activity and a strong use of soil on its banks continued for decades. This river suffered a serious accident at 2015 due to a rupture of a tailings dam in your upper course, characterizing it as the biggest Southern Hemisphere accident in the mineral area. This work determined the radioactivity levels in sediments of the Doce River estuary from samples collected before and after the rupture. The concentrations analyzed by gamma spectrometry with Ge detector for 238U, 232Th, 226Ra, including 210Pb and 40K in sediments, ranged from [(15.86 ± 0.99), (19.83 ± 1.10), (55.65 ± 7.71), (11.58 ± 4.43) and (237.15 ± 8.70)] Bq kg-1 before the breakup, respectively, for [(20.70 ± 0.99) (31.82 ± 1.30), (90.84 ± 8.50) (11.41 ± 4.04) and ( 197.50 ± 7.62)] Bq kg-1, in the period after the breakup, respectively. This study identified an increase in 238U, 232Th and 226Ra concentrations after the rupture. It was evaluated the annual effective dose equivalent to the local population and the radiological risks, both internal and external, second model UNSCEAR. The results obtained for the radiological risk on the local population were compared with the world values obtained in similar environments for these radionuclides.

Natural and artificial radioactivity levels in sediments along the Kenyan coast

Natural and artificial radioactivity levels in sediments along the Kenyan coast

Natural and artificial radioactivity levels in sediments in Algiers bay

Natural ( 238U and 232Th series, 40K) and artificial ( 137Cs) radioactivity levels in the sediments of Algiers bay were measured using gamma-ray spectrometry. Concentrations (Bq kg −1, dry weight) have been observed to range from 10.8 to 25.0 for 238U, from 6.5 to 31.7 for 232Th, from 55.9 to 607.4 for 40K and from 0.95 to 9.5 for 137Cs. These values are discussed in terms of the facies type of the sea bottom.