Twenty three marine sediment samples taken from the side beach from the Abyan beach, Aden Gulf, Yemen to measuring the activity concentration of terrestrial radionuclides radium-226, thorium-232 and potassium-40 and its associated hazard indices using gamma spectrometer with High-Purity Germanium HPGe detector. The average activity concentration of natural radionuclides 226Ra, 232Th and 40k in marine sediments samples under investigation were 16.25± 0.63Bqkg-1, for Ra-226, 23.80± 1.46Bqkg-1 for Th-232 and 518.54±44.61Bqkg-1 for K-40 respectively. The radiation hazard indices which resulting from the presence of natural radionuclides in marine sediment samples were calculated and the obtained results indicate that the average value of radium equivalent activity was 90.21Bqkg-1. The average value of External hazard index Hex was 0.243 and the average values of internal hazard index Hin was 0.287. The average value of outdoor absorbed dose rate Dout was 43.66nGyh−1 and indoor absorbed dose rate Din was 83.13nGyh−1. The average values of annual outdoor effective dose AEDout was 0.053mSvy-1and the annual indoor effective dose AEDin was 0.407mSvy-1. The average values of the annual gonadal dose equivalent AGDE were 312.52μSvy-1. While the average values of outdoor excess life-time cancer risk ELCRout was 0.187×10−3 and the indoor excess life-time cancer risk ELCRin was 1.427×10−3. They are less than worldwide limits.

The behavior of radon in marine sediments collected from Abian beach, Abian Governorate, Aden Gulf, Yemen, was studied by using Alpha Guard PQ2000 PRO radon detector. The activity concentration of radon in the sediments was found to be ranging from 64.84 to 166.93±11.85Bq.m-3 with mean value 103.88±8.80Bq.m-3. The radium content in the sediments ranged from 20.01 to 56.06Bqkg-1 with mean value 33.51Bqkg-1 , while the area exhalation rate of 222 Rn ranged from 6.73 to 18.49Bqm-2 h-1 with mean value 11.22Bqm-2 h-1 also the mass exhalation rate of 222 Rn ranged from 0.151 to 0.424Bqkg-1 h-1 with mean value 0.253Bqkg-1 h-1 , respectively for the studied samples of marine sediments. The annual effective dose was found to be ranging from 1.63 to 4.21mSvy-1 , with an average of 2.62mSvy-1. Average value of radon concentrations from marine sediments samples were compared with other literature values.