RADIOACTIVITYCONCENTRATIONS IN SOIL AND VEGETABLES FROMTHE NORTHERN JORDAN RIFT VALLEY AND THE CORRESPONDING DOSE ESTIMATES Anas M. Ababneh*, Maisoun S. Masa’deh, Zaid Q. Ababneh, Mufeed A. Awawdeh and Abdalmajeid M. Alyassin Physics Department, Yarmouk University, Irbid 21163, Jordan Received January 27 2009, revised March 18 2009, accepted March 26 2009 The Jordan Rift Valley (JRV) is considered the food bowl of Jordan, especially during the winter season. In this study, soil and vegetable samples collected from greenhouses in the northern JRV were analysed for their radioactive content. The activity concentrations of 238 U, 235 U, 232 Th, 226 Ra, 137 Cs and 40 K in soil were found to be ( +SD) 33 + 12, 2.2 + 0.7, 11.2 + 3.3, 40.5 + 15.5, 3.5 + 1.3 and 156.0 + 46.6 (Bq kg 21 ), respectively. In vegetables, the activity concentration of 40 K was found in the range of 698–1439 Bq kg 21 , while those of 226 Ra and 228 Ra were found to be in the range of <0.61–2.56 and <0.69 – 3.35 Bq kg 21 , respectively. Transfer factors for 40 Kwere found to be high and ranged from 5 to 8, while those for 226 Ra and 228 Ra were found to be from <0.01 to 0.07 and from <0.09 to 0.42, respectively. The calculated external annual effective dose is found to be within the worldwide range. INTRODUCTION It is inevitable that all populations have been subject to radiation exposure from external and internal sources almost every day of their lives. The greatest contribution of irradiation to the human body comes from natural sources, which are emitted from the members of the natural decay series as well as from the radioisotope of potassium 40 K. In addition to the natural sources, the environment has been considerably affected from man-made sources such as those produced artificially through nuclear reac- tions, thermonuclear weapons testing and the Chernoby1 power station accident in 1986 (1) . The latter released large quantities of radionuclides, mainly 137 Cs and 90 Sr, into the atmosphere, which contaminated the environment of several countries including the Mediterranean. Among the artificial radionuclides, 137 Cs has received significant attention because of its relatively long half-life (about 30 y) and its faster uptake by roots, through direct compe- tition between Cs and K ions during the process of accumulation throughout the plant (2 – 6) . Agricultural products are usually contaminated either directly or indirectly with natural and artificial radionuclides. Therefore, consumption of such pro- ducts increases the internal radiation dose to the humans and contributes a large portion to the mean annual effective dose (7) . One of the major factors influencing the dose assessment of human exposure to radionuclides via the food chain in a contaminated region is the transfer factors (TFs) of radionuclides from soil to plants (8) . Such factors vary from one plant to the other and depend, in general, on the physical and chemical properties of the soil, environmental conditions and chemical form of the radionuclide in the soil (9,10) . Several studies have been carried out to determine TFs for various plants in different regions (3,4,9 – 17) . In general, the radioactivity concentration in plant increases with that in soil in a linear fashion, especially for high soil activity concentrations (10 – 12,18,19) . In Jordan, several studies have been conducted on measuring the activity concentrations of natural and artificial radioactivity in the environment (17,20 – 23) . Most of these studies focused either on undisturbed or populated regions and few on agricultural soil or foodstuff (17) . The present work aims to determine the activity concentrations of gamma-emitting radionuclides in soil and different agricultural crops grown in the Jordan Rift Valley (JRV), which is considered as the food bowl of Jordan, especially during the winter season, as it contains about 65% of the total number of greenhouses in Jordan that produce more than 70% of Jordanian vegetables during the winter season (24) . Assessing the radio- active content (both natural and anthropogenic) in this area is, thus, of crucial importance to the public health of Jordan. Another goal is to estimate the soil-to-plant TFs and to estimate the annual effective dose to the public from the soil. Moreover, the present work is part of a continual effort to establish a baseline for the radioactivity content in Jordan. *Corresponding author: ababneha@yu.edu.jo # The Author 2009. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org Radiation Protection Dosimetry (2009), Vol. 134, No. 1, pp. 30–37 doi:10.1093/rpd/ncp064 Advance Access publication 22 April 2009