Assessment of gamma absorbed doses and radiological risk indexes from soil radioactivity around the phosphate area in south Tunisia.

Human beings are constantly exposed to the radiations coming from the environment. This work assesses the radiological hazards of natural radioactivity in soil samples taken at four locations around the phosphate area in south Tunisia. Concentrations of primordial radionuclides were measured by gamma spectrometer using an HPGe detector. The overall mean values of 40K, 226Ra and 232Th concentrations were 264, 27 and 13 Bq kg-1, respectively. From the radioactivity measurements, radiation hazard indices specified by the United Nation Scientific Committee on the Effect of Atomic Radiation such as radium equivalent activity (Raeq), absorbed dose rates ($ {\dot{\text D}} $) and annual effective dose (AED) to the population for outdoor environment were determined. The mean values for the abovementioned parameters were 64 Bq kg-1, 33 nGy h-1 and 40 µSv y-1, respectively.

Assessment of radionuclide transfer factors and transfer coefficients near phosphate industrial areas of South Tunisia.

The activity concentrations of naturally occurring and anthropogenic radionuclides in agriculture soils as well as in several food products at four locations within the phosphate area of South Tunisia were investigated. Soil-to-plant transfer factors as well as feed-to-animal products transfer coefficients were determined for the first time for the region. Activity concentrations of 40K, 210Pb, 226Ra, 228Ra and 137Cs in soils of agriculture fields were lower than worldwide average values. The soil-to-plant transfer factors (TFs) for 40K in leafy vegetables were higher than those in fruit vegetables. Soil-to-grass transfer factor (Fv) values were in the following order: 40K > 210Pb > 226Ra. The grass-to-milk transfer coefficient (Fm) values for 40K and 210Pb ranged between 2 × 10-3 and 4 × 10-3(day L-1). The concentration ratios for the animal products (CRmilk-feed, CRmeat-feed and CRegg-feed) varied in the ranges of 2 × 10-2-4 × 10-2 L kg-1, 1 × 10-2-2 × 10-1 (L kg-1) and 5 × 10-2-1 (L kg-1)for 40K, 210Pb and 226Ra, respectively. Transfer parameters determined in the present study were compared with those reported in International Atomic Energy Agency reports and other published values. The absorbed gamma dose rate in air and the external hazard index associated with these natural radionuclides were computed to assess the radiation hazard of radioactivity in this region, and the results indicated that these areas are within set safety limits.

BASELINE STUDIES ON RADIONUCLIDE CONCENTRATION IN FOOD MATERIALS AND ESTIMATION OF THE COMMITTED RADIATION DOSE AROUND THE PHOSPHATE INDUSTRIAL AREA OF SOUTH TUNISIA.

The activity concentration of natural and anthropogenic radionuclides was determined in different vegetable samples, and foods derived from animal origin, from different locations in the four cities of Southern Tunisia, where large-scale phosphate industries are operating. The aim of the studies was to establish a baseline database on radionuclide concentration in food materials and to evaluate the radiation dose to the general population due to its ingestion through the food chain. The activity concentrations of 40K, 210Pb, 226Ra, 228Ra and 137Cs was determined by gamma spectrometry using a HPGe detector, and from the measured activity concentrations, the doses were estimated using the dose coefficients given by the ICRP. The dose due to intake of radionuclides through mineral water was also determined. The total annual effective doses were found to be 2.2, 1.4, and 0.7 mSv y-1 for 1 y, 5-15 y and adult (>17 y) age groups, respectively. Among the radionuclides studied, 210Po was the highest contributor to the total dose, followed by 210Pb.