THE ACTIVITY CONCENTRATIONS AND HAZARD INDICES IN SEDIMENT SAMPLES FROM THE AFRICAN COASTS

Abstract

In this work we have been interested in a compilation of data covering the period from 2000 to present of radionuclide activity concentrations in estuary or marine sediments of the African continent. So, we included three radionuclides as the most representative of natural radioactivity (²²⁶Ra, ²³²Th and ⁴⁰K) in sediment samples taken from 20 coastal areas, by considering the Atlantic Ocean (Nigeria, Ghana, Morocco and Canary Islands), the Mediterranean Sea (Spain and Egypt) and the Red Sea (Egypt). Therefore, we have relied on scientific publications as well as on our own results.

Moreover, to characterize the potential radiation dose to humans resulting from exposure to sediment natural radioactivity, eight radiological hazard indices were estimated: Total Absorbed Dose Rate in air (D), Annual Effective Dose Equivalent (AEDE), Annual Gonadal Dose Equivalent (AGDE), Radium Equivalent Activity (Ra_eq), External Hazard Index (H_ex), Internal Hazard Index (H_in), Gamma Index (Ig) and Excess Lifetime Cancer Risk (ELCR).

The highest activity concentrations were found in sediment samples in Atlantic Ocean, especially in one site in Nigeria with a great exceed of the World Wide Average concentrations of ²²⁶Ra, ²³²Thand ⁴⁰K, which are 35, 30 and 400 Bq Kg-¹ respectively.

Also, the calculation of the eight radiological hazard indices indicated significant radiological risks always in the same site in Nigeria in Atlantic Ocean.