Fahad I. Almasoud

MEASUREMENT OF RADON LEVELS IN GROUNDWATER SUPPLIES OF RIYADH WITH LIQUID SCINTILLATION COUNTER AND THE ASSOCIATED RADIATION DOSE

A national groundwater surveillance programme was started for investigation of natural radioactivity levels in the year 2007. This paper presents (222)Rn radioactivity concentration levels in well waters located in and around the city of Riyadh in Saudi Arabia. Water samples were collected from 171 wells in six different locations. Most of these deep wells have an approximate depth of 1000 m, while shallow wells have a depth of 300 m. The analyses were performed by an ultra-low level liquid scintillation spectrometer equipped with an alpha-beta discrimination device. Efficiency and background calibrations were performed with a (226)Ra aqueous standard homogeneously mixed with a cocktail (high efficiency mineral oil scintillator) which was used after a certain period of time to assure radon equilibrium. The measured (222)Rn activities of deep wells ranged from 0.34±0.05 to 3.52±0.30 Bq l(-1) (average: 1.01±0.10 Bq l(-1)), whereas those of shallow wells ranged from 0.72±0.08 to 7.21±0.58 Bq l(-1) (average: 2.74±0.24 Bq l(-1)). The (222)Rn concentrations levels were found to be in compliance with the proposed national limits of 11.1 Bql(-1) and depend on the water source.

Radium-228 analysis of natural waters by Cherenkov counting of Actinium-228

The activities of (228)Ra in natural waters were determined by the Cherenkov counting of the daughter nuclide (228)Ac. The radium was pre-concentrated on MnO(2) and the radium purified via ion exchange and, after a 2-day period of incubation to allow for secular equilibrium between the parent-daughter (228)Ra((228)Ac), the daughter nuclide (228)Ac was isolated by ion exchange according to the method of Nour et al. [2004. Radium-228 determination of natural waters via concentration on manganese dioxide and separation using Diphonix ion exchange resin. Appl. Radiat. Isot. 61, 1173-1178]. The Cherenkov photons produced by (228)Ac were counted directly without the addition of any scintillation reagents. The optimum Cherenkov counting window, sample volume, and vial type were determined experimentally to achieve optimum Cherenkov photon detection efficiency and lowest background count rates. An optimum detection efficiency of 10.9+/-0.1% was measured for (228)Ac by Cherenkov counting with a very low Cherenkov photon background of 0.317+/-0.013cpm. The addition of sodium salicylate into the sample counting vial at a concentration of 0.1g/mL yielded a more than 3-fold increase in the Cherenkov detection efficiency of (228)Ac to 38%. Tests of the Cherenkov counting technique were conducted with several water standards of known activity and the results obtained compared closely with a conventional liquid scintillation counting technique. The advantages and disadvantages of Cherenkov counting compared to liquid scintillation counting methods are discussed. Advantages include much lower Cherenkov background count rates and consequently lower minimal detectable activities for (228)Ra and no need for expensive environmentally unfriendly liquid scintillation cocktails. The disadvantages of the Cherenkov counting method include the need to measure (228)Ac Cherenkov photon detection efficiency and optimum Cherenkov counting volume, which are not at all required when liquid scintillation analysis is used.

Accumulation of uranium by filamentous green algae under natural environmental conditions

The capacity of algae to concentrate uranium under natural environmental conditions is measured by a-spectrometry. Spirogyra, a filamentous green fresh-water alga, has concentrated uranium from a surface concrete ponds with elevated uranium levels (140-1140 ppb). The concentration factors (CFs) ranged from 8.9-67 with an average value of 22.Cladophora spp, a filamentous green marine alga has concentrated uranium from the marine water with a concentration factor ranged from 220–280. The average concentration factor was 250. The factors affecting the sorption process are discussed in detail.

Determination of natural radioactivity in irrigation water of drilled wells in northwestern Saudi Arabia.

The levels of natural radiation in bedrock groundwater extracted from drilled wells in selected farms in the northwestern part of Saudi Arabia were addressed. The investigated waters form a source of irrigation for vegetables, agricultural crops, wheat, and alfalfa to feed livestock consumed by the general public. Information about water radioactivity in this area is not available yet. Therefore, this study strives to contribute to the quality assessment of the groundwater of these wells that are drilled into the non-renewable Saq sandstone aquifer. Hence, gross alpha and beta activities as well as the concentrations of (224)Ra, (226)Ra, (228)Ra, (234)U, (238)U, and U(total) were measured, compared to national and international limits and contrasted with data quoted from the literature. Correlations between the activities of the analyzed radionuclides were discussed. The concentrations of gross alpha and beta activities as well as (228)Ra were identified by liquid scintillation counting whereas alpha spectrometry was used to determine (224)Ra, (226)Ra, (234)U and (238)U after separation from the matrix by extraction chromatography. The mean activity concentrations of gross α and β were 3.15 ± 0.26 Bq L(-1) and 5.39 ± 0.44 Bq L(-1), respectively. Radium isotopes ((228)Ra and (226)Ra) showed mean concentrations of 3.16 ± 0.17 Bq L(-1) and 1.12 ± 0.07 Bq L(-1), respectively, whereas lower levels of uranium isotopes ((234)U and (238)U) were obtained.

Activity Concentrations and Dose Assessment of Gamma Emitting Radionuclides in Canned Tuna and Sardines Produced after the Fukushima Nuclear Accident.

AbstractThe aim of the present work was to investigate the radioactivity concentrations of gamma emitting radionuclides in canned tuna and sardines that were produced after the Fukushima nuclear accident and to assess the resulting radiation doses to the public. Fifty-eight brands of canned tuna and sardines consumed in the Middle East and produced from different parts of the world were analyzed using a germanium detector. Cesium-137 (137Cs) was not detected above the minimum detectable activity in any of the samples. Natural radionuclides 40K, 226Ra and 228Ra were detected with wide activity concentration ranges and with average values of (in Bq kg−1 wet weight): 68 ± 36, 0.31 ± 0.45, 0.34 ± 0.25, respectively, in tuna samples and with averages of 129 ± 67, 0.20 ± 0.33, 0.60 ± 0.31 in sardine samples. The results of the activity concentrations of 40K and 226Ra showed some regional dependence. Tuna samples produced in Europe have almost twice the concentration of 40K and half the concentration of 226Ra as compared to samples produced in either East or South Asia and North America. Moreover, sardine samples produced in North Africa and Europe have almost twice the concentrations of 40K and 226Ra as those produced in East or South Asia and North America. Dose assessment due to ingestion of canned seafood was also performed, and the committed effective dose was found to be well within the worldwide average.

A STUDY OF THE RADIOACTIVITY IN THE DUST STORM EVENT OF APRIL 2015 IN ARABIAN PENINSULA

Gulf countries are often affected by dust storms which have a significant influence on the environment and public health. The present work examines the radioactivity content in the intense dust storm occurred over Gulf countries on 1 April 2015. The results showed that the average value of 137Cs in dust samples (±SD) is 14.4 ± 1.6 Bq/kg, which is almost two orders of magnitude larger than those in soil samples. 7Be was detected with a considerable amount only in dust samples. The activity concentrations of the natural radionuclides (234,238U, 228,230,232Th, 226,228Ra and 40K) in dust samples were found to be approximately two to three times higher than the corresponding values in soil samples, which is attributed to the abundance of the finest particle size in the dust samples. Also, the activity ratios and the correlations between the detected radionuclides were investigated to assess the origin and activities associated with any variation of the radionuclides in the environment. Moreover, the total annual effective dose due to ingestion of dust was estimated to be 89.7 and 34.9 nSv for infants and adults, respectively, which is well below the world average internal dose of 290 μSv. The main contributor to the annual effective dose was 228Ra, which contributes ~69.6 and 43.3% for infants and adults, respectively, followed by: 226Ra » 232,230,228Th > 234,238U > 40k, 137Cs » 7Be.

Assessment of the committed effective dose due to the 210Po intake from fish consumption for the Arabian Gulf population

This study aims to assess the committed effective dose due to the intake of 210Po from the consumption of fish in Arabian Gulf countries. Twenty different kinds of fish, which represent the most common fish species consumed in the Arabian Gulf countries, were analyzed using alpha spectrometer technique. 210Po activity concentrations in fish samples were found to vary over a wide range from 0.1 to 14.7 Bq kg-1 fresh weight. This variation of 210Po concentrations between various type of fish samples might be attributed to the feeding type pattern and the size of fish. The annual committed effective dose due to ingestion of 210Po in fish species for adults in the Arabian Gulf countries was estimated and found to vary from 38 μSv in Bahrain to 85 μSv in Oman with an average value of 59 μSv. These values are considered relatively high compared to those reported in some other regions. However, it is still much lower than the world average ingestion dose due to natural radiation sources.