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

Abstract

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.