Radioactivity levels and radiological hazard indices at the Saudi coastline of the Gulf of Aqaba

The coast of the Gulf of Aqaba is subjected to several sources of pollution due to several activities occurring at the coastal area. The activities vary between industrial, tourist and other development aspects at the Jordanian coastline of the Gulf of Aqaba. Phosphate industry has been considered a major source polluting the marine environment. According to official reports, 4-7 million tons of raw phosphate is exported through the Gulf of Aqaba. During transportation and loading, a small proportion of this enters the waters of the Gulf. Phosphate dust has also been considered another source of nutrients loading to the Gulf. 19 sediment samples were collected along the Saudi Gulf coastline, from the Saudi-Jordan border down to the end of the Gulf at Tiran Strait. Measurements of the activity concentrations of Ra-226, Th-232, K-40 and Cs-137 in Bq/kg (in dry weight) of the collected samples were carried out using gamma-ray spectrometry based on a highly pure germanium coaxial detector (HPGe). The concentrations of U-238 and Th-232 were also determined using ICP-MS technique. The average specific activities for Ra-226, Th-232, K-40 and Cs-137 were found to be 11.4 +/- 1.5, 22.5 +/- 3.7, 641.1 +/- 61.3 and 3.5 +/- 0.7 Bq/kg, respectively. The results show that the mean activity of Ra-226 and Th-232 is lower than the world average of 25 Bq/kg for both of them, whereas the mean value for K-40 is about double the world average of 370 Bq/kg. The presence of Cs-137 in the analyzed samples is low in most locations. The mean concentrations of U-238 and Th-232 in the study area are 1.2 and 5.4 mg/kg, respectively, and the ratio U-238/Th-232 is 0.2, which is lower than the global ratio of 0.3. The ratio of Ra-226/Ra-228 was found to decrease southwards in the direction of Tiran Strait, away from the phosphate industry in Jordan. Mean values for radium equivalent, absorbed dose, annual effective dose, external and internal hazard index and representative level index were determined as: 92.9 Bq/kg, 45.6 nGy/h, 56.0 ptSv/y, 0.13, 0.28 and 0.73, respectively. (C) 2010 Elsevier Ltd. All rights reserved.