Adam Khatir Sam

Radioactivity levels in the Red Sea coastal environment of Sudan

Measurements of natural and fallout radionuclides in marine surface sediments, seagrass and algae collected from the Sudanese coastal waters of the Red Sea have been made using high resolution γ-spectrometry, radiochemical separation and α-spectrometry. Activity levels of uranium isotopes, thorium isotopes, 226Ra, 210Po, 40K and 137Cs were determined in the samples. Comparison of the data on natural radionuclides from coastal marine sediments with those collected from 30 km offshore (Sanganeb atoll) reveals that both anthropogenic and terrestrial influx from the hinterland is negligible. However, values for 226Ra and 210Po are higher in the sediments of Port Sudan harbour relative to those from the adjacent fringing reefs. Uranium content is higher in shallow-water sediments and the authigenic fraction constitutes 12% on the average. The 228Th:232Th disequilibrium in sediments indicates rapid rate of sedimentation at the sampling sites. The activity levels detected for 137Cs in sediments collected from the Port Sudan harbour area are fairly high as compared with values from other sampling locations. On the basis of individual data, the variations are insignificant with regard to the uptake of natural radionuclides by marine species considered in this study. However, 137Cs activity in algae ranged from 0.33 to 1.32 Bq kg−1 with Sargassum (brown algae) showing the highest level.

The natural radioactivity in phosphate deposits from Sudan

Abstract The natural radionuclide content of phosphate deposits at Uro and Kurun in Eastern Nuba mountains in the state of Kordofan (Western Sudan) and soils was determined radiochemically and gamma spectrometrically. The analyses were performed for natural uranium and thorium, 210 Po, 226 Ra and 40 K. The data indicate that 238 U and its decay products contribute primarily to the high natural radioactivity of phosphate ores. At maximum, we found an activity concentration of 2600 Bq/kg natural 238 U. From the values obtained, the dose rates over agricultural areas, resulting from the use of ground rock phosphate as fertilizers estimated under extremely conservative assumptions, result in an additional external radiation exposure for members of the population of 5.42 × 10 −9 nGy/a and 1.13 × 10 −9 nGy/a for Uro and Kurun rock phosphates, respectively. These results show that the natural radionuclides contained in Uro and Kurun ground rock phosphate contribute very little to the average terrestrial radiation exposure to the population.

Distribution of some natural and anthropogenic radionuclides in Sudanese harbour sediments

The distribution of some natural and anthropogenic radionuclides (226Ra,228Ra,210Po,40K,137Cs) in surface marine sediments from the harbours at Port Sudan and Sawakin on the Sudanese coast of the Red Sea has been investigated using α-spectrometry and direct high-resolution γ-spectrometry. The prime ams were to assess the levels of radioactivity and the influence of factors such as dredging and the organic matter content of the sediments on the distribution pattern of the radionuclides. The results have been evaluated and the leves indicate the absence of any possible enhancement by anthropogenic influx from the hinterland. The spatial distribution pattern is more heterogeneous in Sawakin harbour where some parts have recently been dredged and the sludge is removed to maintain the required depth. The data also show an insignificant relationship between the activity concentrations of all the radionuclides and the content of organic matter in the sediments.

Assessment of Committed Effective Dose due to consumption of Red Sea coral reef fishes collected from the local market (Sudan)

An assessment of Committed Effective Dose (CED) due to consumption of Red Sea fish containing (210)Po and (137)Cs was performed for 23 different marine fish samples collected from the local market at Port Sudan. The fish were classified according to their feeding habits into three categories: carnivores, herbivores, and omnivores. Measured activity concentrations of (210)Po were found in the ranges 0.25-6.42 (carnivores), 0.7-5 (omnivores) and 1.5-3.8 (herbivores) Bq/kg fresh weight. In the same study, activity concentrations of Cs-137 were determined to be in the ranges 0.1-0.46 (carnivores), 0.09-0.35 (omnivores) and 0.09-0.32 (herbivores) Bq/kg fresh weight, which were several times lower than those of (210)Po. Appropriate conversion factors were used to derive the CED, which was found to be 0.012, 0.01 and 0.01 (microSv/yr) in carnivores, omnivores and herbivores, respectively, for (137)Cs. This contributes about 0.4% of the total dose exclusively by ingestion of fish. For (210)Po, it was found to be 3.47, 4.81 and 4.14 (microSv/yr) in carnivores, omnivores and herbivores, respectively, which represents 99.6% of the total dose (exclusively by ingestion of fish). The results of CED calculations suggest that the dose received by the Sudanese population from the consumption of marine fish is rather small and that the contribution of (137)Cs is negligible compared to (210)Po.

Radium-226 uptake by vegetation grown in Western Sudan

Abstract A study of the uptake of 226Ra by cultivated crop plants was carried out in uncontaminated regions of purely natural radioactivity. Activity concentration of 226Ra in soil and plant samples was measured. In farm soils analysed, the total activity concentration ranged from 14.4–79.1 Bq/kg and the exchangeable fraction constituted 7.1–27.8% of the total radium content. In the plants analysed, activity concentration levels found ranged from 0.7–23 Bq/kg and 0.1–7.6 Bq/kg dry weight for vegetative and edible crop parts, respectively. Soil/plant CRs related to exchangeable radium showed ranges of 0.09–3.31 and 0.01–0.34 for vegetative and edible crop parts, respectively. Soil pH, organic matter content (OM%), clay content, exchangeable cations (potassium, calcium and magnesium) and available phosphorus were determined with the aim to investigate their influence on radium uptake. Our results also show the existence of a tendency for a lower transfer of radium to edible parts than to the vegetative parts.

Distribution of 226Ra–210Pb–210Po in marine biota and surface sediments of the Red Sea, Sudan

Activity concentration levels and ratios of (226)Ra, (210)Pb and (210)Po are presented in multicellular marine algae, molluscs, coral as well as in surface marine sediments collected from the shallower waters of the fringing reefs area extending towards north and south (Flamingo bay) of PortSudan harbour, Sudan. The analyses were performed adopting alpha-spectrometry, liquid scintillation and Cerenkov counting techniques. Surface sediments from this coastal region are poor in their radioactivity content in contrast to similar data reported from different coastal areas around the globe. There is surface enrichment of (210)Pb and (210)Po with respect to their progenitor (226)Ra as it is evident from the activity ratios of (210)Pb/(226)Ra (3.03+/-1.79) and (210)Po/(226)Ra (2.23+/-1.56). Among marine plants and animals investigated, the green algae species, Halimeda, and coral species, Favites, show substantial concentration of radium at 8.2Bq/kg and 21.9Bq/kg dry weight, respectively. Similarly, the highest concentration of (210)Po was met in Favites at 38.7Bq/kg followed by brown algae, Cystoseria sp., at 32.6Bq/kg. There is no variation seen among algal species for (210)Pb uptake, however, converse to radium and polonium, Favites (coral) was found to contain the minimum concentration of lead (3.88Bq/kg). In most species there is preferential accumulation of polonium over its parent radium as indicated by (210)Po:(226)Ra activity ratio with Cystoseria (brown algae) showing the highest value at 8.81. On the other hand, (210)Po:(210)Pb activity concentration ratio revealed that coral species Favites (9.97) and the brown algae Sargassum (1.85) have a greater tendency to accumulate (210)Po over (210)Pb, while in the rest of species; this ratio is less than unity.

Plutonium Isotopes in Sediments from the Sudanese Coast of the Red Sea

This paper presents the activity concentrations of Pu isotopes in surface marine sediments collected from the Sudanese coast of the Red Sea. The following concentration ranges were determined: 238Pu, 4.7–28.6 mBq/kg; 239+240Pu, 53–343 mBq/kg dry weight. The average activity ratios of 238Pu/239+240Pu (0.075±0.045 mBqk/kg) and 239+240Pu/137Cs (0.026±0.025 mBq/kg) are appropriately comparable to the literature values that are characteristic of the global fallout from the atmospheric nuclear weapon tests. However, 239+240Pu/137Cs ratio in sediments collected from the biologically rich fringing reef is an order of magnitude higher compared to other sampling locations.

Uranium and thorium isotopes in some red sea sediments

Alpha-emitting isotopes of uranium and thorium in surface marine sediments collected from the harbours at Port Sudan and Sawakin on the Sudanese coast of the Red Sea have been studied using radiochemical separation procedures and alpha-particle spectrometry. Activity concentrations of 238U, 235U, 234U, 232Th, 230Th and 228Th were measured. The ranges of activities observed for 238U and 232Th were 2.71-13.42 Bq/kg and 3.62-18.73 Bq/kg from Port Sudan and 3.87-24.79 Bq/kg and 1.13-10.04 Bq/kg dry weight from Sawakin, respectively. The behaviour of these decay-series nuclides was examined using daughter/parent and non-isotopic specific activity ratios in sediments. Simple regression analysis showed insignificant correlation between uranium and thorium activities and the organic matter content in sediments. The results are compared with those from coastal waters of other oceans.

Radiation survey of aircraft and heavy machinery scrap.

This study was conducted primarily to survey aircraft and heavy machinery at 30 locations within Khartoum State using handheld radiation survey meters to detect and identify any radiation sources that might be present and to estimate radiation dose levels. The survey has resulted in detection of 16 sealed sources of (90)Sr and one of (226)Ra in aircraft scrap. Of course, (90)Sr sources are used in military aircraft as temperature sensors while (226)Ra is used for indicating fuel levels. These sources were found intact without spreading radioactivity contamination; however, none was detected in heavy machine scrap. The levels of radiation dose measured at 0.1m from the source fall within the range of 25.1-40.2 μSv/h with an average value of 33.52 ± 4.06 μSv/h. These orphan sources have been separated from the scrap, tested for possible leakage, conditioned and stored in waste management facility. The result of this study has revealed without doubt that the scrap constitute a serious source of public exposure and highlights the importance of legislation making radiation monitoring of scrap in the country mandatory before it is sold to metal industry for reprocessing.

RADIOLOGICAL HAZARD INDICES OF GRANITIC ROCKS USED FOR THE CONSTRUCTION OF BUILDINGS FROM NUBA MOUNTAINS SUDAN

This study was conducted to assess the level of radioactivity and the radiation hazards associated with granite rocks used for construction of buildings. The measurement of radioactivity content of the rock samples was performed with gamma-spectrometry equipped with Nal (TI) detector. From the results obtained in this study the average activity concentrations of 226Ra, 232Th and 40K were 20.64, 30.50 and 295.19 Bq kg-1, respectively. The absorbed dose rate in air at 1 m above ground level, the annual effective dose and the gamma index were determined with the aim to assess the possible radiological impact on inhabitants of dwellings built using such rocks. The mean value of the absorbed dose rate, the annual effective dose and the gamma index (Iγ) was 36.36 nGy h-1, 40.79 μSv y-1 and 0.51 μSv y-1, respectively. Radium equivalent activities, and external and internal hazard indices, were also calculated. These data indicated that the area of study lies within areas recognized as normal background radiation and the granite rocks are safe to be used as building material and other structural purposes.