Natural and artificial radioactivity levels in sediments in Algiers bay

LEVELS OF NATURAL AND ANTHROPOGENIC RADIONUCLIDES IN SEDIMENTS OF SOME MOROCCAN COASTAL AREAS AND DOSE ASSESSMENT BASED ON ERICA TOOL

In this work, we considered the concentrations of natural and anthropogenic radionuclides (namely the 40K, 210Pb, 226Ra, 137Cs, 234Th, 228Th and 228Ra) in sediments from Moroccan coast areas by considering estuaries (Sebou and Loukkos) and marine ecosystems (M'diq Bay and three Lagoons: Moulay Bousselham, Sidi Moussa and Oualidia). Sediment samples were analyzed using Gamma spectrometry. The objective was to establish radioactivity levels in Moroccan coastal areas as well as radiological risk assessment by using the ERICA tool. The software allows the estimation of dose rates to biota (a set of reference organisms by default). The highest activity concentrations were found in sediment samples of Sidi Moussa Lagoon, possibly due to the anthropogenic activities, while the lowest levels were reported in Sebou estuary, attributed most probably to a flooding event that occurred in the same year of sampling. Also, 210Pb and 40K have the most significant concentrations, while 137Cs has the lowest concentrations with a great resemblance with similar works. The World Wide Average concentration of 226Ra was exceeded in the three lagoons and that of 40K only exceeded at Sidi Moussa Lagoon. The application of ERICA tool allowed the assessment of total dose rates that are mainly due to internal exposure with strong contribution of 226Ra mainly for phytoplankton in the case of marine ecosystems and insect larvae, mollusc-bivalve, mollusc-gastropod and zooplankton for estuary ecosystems. The total dose rates were far lesser than the admissible dose rate proposed by ERICA tool (10 μGy h-1) and, therefore, unlikely to cause harmful effects to organisms.

Determination of uranium and thorium concentrations in sediment samples by using solid state nuclear track detectors

In this study, uranium and thorium concentrations in the sediment samples collected from the Gulf of Izmit in Marmara Sea were determined using neutron radiography method and alpha-autoradiography method. Mean uranium concentrations calculated for the sediment samples collected from the boreholes S2, S3, S5, S8 and KS-2 were found to be 5.99 μg/g (3.58-8.16 μg/g), 4,59 μg/g (2.54-8.22 μg/g), 4.03 μg/g (2.13-6.9 μg/g), 3.71 μg/g (2.36-4.48 μg/g) and 2.81 μg/g (2.16-4.06 μg/g), respectively. The highest uranium concentration in all borehole samples was obtained from borehole S3 with a value of 8.22 μg/g at a depth of 77.00 m, followed by borehole S2 with a value of 8.16 μg/g at 76.95 m depth. These results also confirms the possibility of thermal sources at boreholes S2 and S3. The mean thorium concentrations in boreholes S3 and S8 were found to be 15.26 μg/g (9.60-17.49 μg/g) and 15.76 μg/g (13.89-17.37 μg/g), respectively. The highest thorium concentration in obtained samples from all boreholes was obtained in borehole S3 with a value of 17.49 μg/g at a depth of 77.00 m.

A review of radioactivity in the Gulf region

The region around the Gulf is moving toward a nuclear energy option with the first nuclear power plant now operational in Bushehr, Iran. Others are soon to be commissioned in Abu Dhabi and in Saudi Arabia. For this reason, radiological safety is becoming a prime concern in the region. This review compiles published data on radionuclide concentrations in seawater, sediment, and biota that have been analyzed in the Gulf countries, along with spatial distribution patterns to enable a synoptic view of the available datasets. The seawater concentrations of ³H, ²¹⁰Po, ²¹⁰Pb, ¹³⁷Cs, and ⁹⁰Sr varied between 130 and 146, 0.48-0.68, 0.75-0.89, 1.25-1.38, 0.57-0.78 mBq L^-1, respectively. The ²²⁶Ra concentration in seawater varied between 0.26 and 3.82 Bq L^-1. Extremely high ⁴⁰K concentrations between 132 and 149 Bq L^-1 have been reported from the Iranian coast compared to 8.9-9.3 Bq L^-1 from the western side of the Gulf. Concentrations of ⁴⁰K, total ²¹⁰Pb, ¹³⁷Cs, ⁹⁰Sr, ²²⁶Ra, ²²⁸Ra, ²³⁸U, ²³⁵U, ²³⁴U, ^239+240Pu, and ²³⁸Pu were determined in sediment and ranged between 353 and 445, 23.6-44.3, 1.0-3.1, 4.8-5.29, 17.3-20.5, 15-16.4, 28.7-31.4, 1.26-1.30, 29.7-30.0, 0.045-0.21 and 0.028-0.03 Bq kg^-1 dry weight, respectively. Significantly higher ¹³⁷Cs values have been reported from the Iranian coast compared to the western coast of the Gulf. Whole fish concentrations of ⁴⁰K, ²²⁶Ra, ²²⁴Ra, ²²⁸Ra, ¹³⁷Cs, ²¹⁰Po and ⁹⁰Sr ranged between 230 and 447, 0.7-7.3, <0.5-6.6, <0.5-15.80, <0.17, 0.88-4.26 and 1.86-5.34 Bq kg^-1 dry weight, respectively. ²¹⁰Po was found to be highly concentrated in several marine organisms with the highest ²¹⁰Po concentration found in the clam Marcia marmorata (193.5-215.6 Bq kg^-1 dry weight). The review highlights the overall paucity of data and inconsistencies in the measurement of radionuclides throughout the Gulf region. Further, since the region is moving toward nuclear energy to meet its increasing energy demand, and coupled with the environmental effects from offshore oil exploration and the heavy impact of climate change, there is a pressing need to undertake a comprehensive marine radioactivity monitoring and assessment effort by conducting a joint cruise in the Gulf with participation of all the adjoining countries. Several recommendations on sampling marine matrixes in the Gulf are given with the aim of improving comparability of radionuclide data from the various studies undertaken in the Gulf region.

Natural radioactivity levels in sediments in Algiers Bay using instrumental neutron activation analysis

The main objective of this study is to evaluate natural radioactivity levels in sediments collected from different points of Algiers bay. Particular attention was paid to understand correlations between the distribution of uranium and thorium and the geomorphological characteristics of the Bay. Instrumental neutron activation analysis (INAA) has been employed in order to measure the isotopic composition and concentration of uranium and thorium, with emphasis on isotopes, 232Th and 238U. The concentrations reported in Bq kg−1 (dry weight) vary between 19.73 and 34.53 for 238U and between 22.26 and 36.02 for 232Th. The obtained results are within the world typical ranges and did not show any anomalous values. Results revealed clear inverse relationship between activity concentration and grain size. The radioactivity content in sediments had a positive correlation with clay and silt percentage, and a negative correlation with sand percentage. The concentration ratios of 232Th/238U are found to be slightly below the world average value unite (3.94) in sediments. Values below unite indicate that the medium is reductor or the existence of an external source of U-contaminated particles in the bay; Values greater than the unit show either depletion of uranium or enrichment of thorium due to alteration or natural processes in these areas. The strong correlation of uranium and Thorium in samples reflects the source of same origin. The results of the study can be used as basic radiometric data for future sedimentological studies. The situation in the Bay of Algiers is reassuring but the risk of possible contamination cannot be excluded and requires constant vigilance for the preservation of the coast and the Mediterranean from all contamination. The results can also be used as reference data for the monitoring of possible radioactive pollution in the future.

Concentrations of selected radionuclides and their spatial distribution in marine sediments from the northwestern Gulf, Kuwait

This study focuses on creating a baseline for ⁴⁰K, ²¹⁰Pb, ¹³⁷Cs, ⁹⁰Sr, ²²⁶Ra, ²²⁸Ra, ²³⁸U, ²³⁵U, ²³⁴U, ^239+240Pu and ²³⁸Pu in marine sediments in the northwestern Gulf. The respective measured concentration ranges were 386-489, 32.3-48.8, 1.5-2.9, 4.53-5.42, 18.3-23.1, 18.8-23.0, 22.3-30.5, 0.99-1.33, 25.6-34.8, 0.30-0.93, and 0.0008-0.00018Bqkg^-1. The levels of these radionuclides are generally comparable to values reported for other marine waters in the northern hemisphere. The ¹³⁷Cs activity in the Gulf sediments offshore Kuwait is an order of magnitude lower compared to sediments from northeastern Iran. Other than that finding, no hot spots were observed in sediments adjacent to power and desalination plants, oil and gas industrial activities or wastewater treatment facilities. These data will serve as a baseline to gauge possible future inputs of radionuclides in the northern Gulf. The calculated average ratio of ²³⁵U/²³⁸U activity in the area is in agreement with the reported figure of the natural uranium ratio, suggesting the absence of depleted uranium (DU) at all the stations. The low concentration of ^239+240Pu suggests that there is no significant source of plutonium except that from atmospheric fallout from weapon testing and possible dry deposition via long-range dust transport.

Assessment of 226Ra, 238U, 232Th, 137Cs and 40K activities from the northern coastline of Oman Sea (water and sediments)

Water and sediment samples were collected from northern coast of Oman Sea covering from Goatr to Hormoz canyon seaport. Water and sediment quality assessment for naturally or anthropogenic radionuclides at Oman Sea as a main strategic golf for trade and transit, is an important issue. Correspondence analysis (CA) by R-mode analysis represents that sigma(T)-temperature-conductivity-O₂ parameters are well-correlated with ²²⁶Ra, ²³²Th and ⁴⁰K. Accordingly Q-mode analysis revealed an indicator samples of ST13W for different radionuclides, ST03W for O₂, and simultaneously ST34W-ST21W-ST08W-ST04W for sigma(T) parameters. The CA results overlapped with factor and cluster analysis results that explained 85.8% of total variance of water samples. Descriptive analysis of sediments indicates more significant variation than water samples. The ²³²Th and ²²⁶Ra generally showing that ST13D to ST25D sediments that restricted to Pi Bashk coastline are concentrated from ¹³⁷Cs and ⁴⁰K. By comparison with reference-values from Iran and other parts of the world, they are acceptable with respect to environmental and radioisotope hazards.

Natural radioactivity assessment of surface sediments in the Yangtze Estuary

The activities of the natural radionuclides (²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K) of the surface sediments in the Yangtze Estuary were determined and used to evaluate radiation hazards in the study area. The of activities of ²³⁸U, ²³²Th, ²²⁶Ra and ⁴⁰K ranges from 14.1 to 62.3, 26.1 to 71.9, 13.7 to 52.3, and 392 to 898Bqkg^-1, respectively, which were comparable to values of other regions in China. The activities of ²³²Th, ⁴⁰K and ²²⁶Ra were clearly different from the global recommended values. The radium equivalent activity was less than the recommended limit of 370Bqkg^-1; therefore, the sediment in this area can be safely used for reclamation. The external hazard index values were less than one. The average absorbed gamma dose rate and annual effective dose equivalent values were slightly greater than the world average value. ²²⁶Ra/²³⁸U and ²³²Th/²³⁸U ratios could potentially be applied for tracing sediment source.

Distribution and environmental impacts of heavy metals and radioactivity in sediment and seawater samples of the Marmara Sea

In this study, the natural and anthropogenic radioactivity levels in the sediment samples collected from the Marmara Sea in Turkey were determined. The average activity concentrations (range) of (226)Ra, (238)U, (232)Th, (40)K and (137)Cs were found to be 23.8 (13.8-34.2) Bq kg(-1), 18.8 (6.4-25.9) Bq kg(-1), 23.02 (6.3-31.1) Bq kg(-1), 558.6 (378.8-693.6) Bq kg(-1) and 9.14 (4.8-16.3) Bq kg(-1), respectively. Our results showed that the average activity concentrations of (226)Ra, (238)U and (232)Th in the sediment samples were within the acceptable limits; whereas the average activity concentration of (40)K in the sediment samples was higher than the worldwide average concentration. The average radium equivalent activity, the average absorbed dose rate and the average external hazard index were calculated as 100.01 Bq kg(-1), 48.32 nGy h(-1) and 0.27, respectively. The average gross alpha and beta activity in the seawater samples were found to be 0.042 Bq L(-1) and 13.402 Bq L(-1), respectively. The gross alpha and beta activity concentrations increased with water depth in the same stations. The average heavy metal concentrations (range) in the sediment samples were 114.6 (21.6-201.7) μg g(-1) for Cr, 568.2 (190.8-1625.1) μg g(-1) for Mn, 39.3 (4.9-83.4) μg g(-1) for Cu, 85.5 (11.0-171.8) μg g(-1) for Zn, 32.9 (9.1-73.1) μg g(-1) for Pb and 49.1 (6.8-103.0) μg g(-1) for Ni. S5 station was heavily polluted by Cr, Cu, Ni and Pb. The results showed that heavy metal enrichment in sediments of the Marmara Sea was widespread.

Investigation of (235)U, (226)Ra, (232)Th, (40)K, (137)Cs, and heavy metal concentrations in Anzali international wetland using high-resolution gamma-ray spectrometry and atomic absorption spectroscopy

Measurements of natural radioactivity levels and heavy metals in sediment and soil samples of the Anzali international wetland were carried out by two HPGe-gamma ray spectrometry and atomic absorption spectroscopy techniques. The concentrations of (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs in sediment samples ranged between 1.05 ± 0.51-5.81 ± 0.61, 18.06 ± 0.63-33.36 ± .0.34, 17.57 ± 0.38-45.84 ± 6.23, 371.88 ± 6.36-652.28 ± 11.60, and 0.43 ± 0.06-63.35 ± 0.94 Bq/kg, while in the soil samples they vary between 2.36-5.97, 22.71-38.37, 29.27-42.89, 472.66-533, and 1.05-9.60 Bq/kg for (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs, respectively. Present results are compared with the available literature data and also with the world average values. The radium equivalent activity was well below the defined limit of 370 Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. Heavy metal concentrations were found to decrease in order as Fe > Mn > Sr > Zn > Cu > Cr > Ni > Pb > Co > Cd. These measurements will serve as background reference levels for the Anzali wetland.

Assessments of radioactivity concentration of natural radionuclides and radiological hazard indices in sediment samples from the East coast of Tamilnadu, India with statistical approach

This paper reports on the distribution of three natural radionuclides (238)U, (232)Th and (40)K in coastal sediments from Pattipulam to Devanampattinam along the East coast of Tamilnadu to establish baseline data for future environmental monitoring. Sediment samples were collected by a Peterson grab samples from 10m water depth parallel to the shore line. Concentration of natural radionuclides were determined using a NaI(Tl) detector based γ-spectrometry. The mean activity concentration is ⩽2.21, 14.29 and 360.23Bqkg(-1) for (238)U, (232)Th and (40)K, respectively. The average activity of (232)Th, (238)U and (40)K is lower when compared to the world average value. Radiological hazard parameters were estimated based on the activity concentrations of (238)U, (232)Th and (40)K to find out any radiation hazard associated with the sediments. The radiological hazard parameters such as radium equivalent activity (Raeq), absorbed gamma dose rates in air (DR), the annual gonadal dose equivalent (AGDE), annual effective dose equivalent (AEDE), external hazard index (Hex) internal hazard index (Hin), activity utilization index (AUI) and excess lifetime cancer (ELCR) associated with the radionuclides were calculated and compared with internationally approved values and the recommended safety limits. Pearson correlation, principal component analysis (PCA) and hierarchical cluster analysis (HCA) have been applied in order to recognize and classify radiological parameters in sediments collected at 22 sites on East coast of Tamilnadu. The values of radiation hazard parameters were comparable to the world averages and below the recommended values. Therefore, coastal sediments do not to pose any significant radiological health risk to the people living in nearby areas along East coast of Tamilnadu. The data obtained in this study will serve as a baseline data in natural radionuclide concentration in sediments along the coastal East coast of Tamilnadu.

Distribution of natural radionuclide concentrations in sediment samples in Didim and Izmir Bay (Aegean Sea-Turkey)

Natural and artificial radionuclide pollutants of the marine environment have been recognized as a serious environmental concern. The natural radioactivity activity concentrations of (226)Ra, (238)U, (232)Th and (40)K were measured by gamma spectrometry in sediment samples collected from two different areas in Aegean Sea Turkish Coast. There is no information about radioactivity level in the study areas sediments so far. The results showed that the concentrations of activity in the sediment samples are 9 ± 0.6 Bq kg(-1)-12 ± 0.7 Bq kg(-1), 7 ± 0.4 Bq kg(-1)-16 ± 1.0 Bq kg(-1), 6 ± 0.3 Bq kg(-1)-16 ± 1.0 Bq kg(-1) and 250 ± 13 Bq kg(-1)-665 ± 33 Bq kg(-1) for (226)Ra, (238)U, (232)Th and (40)K, respectively. In general, the distribution of activity concentrations along the coast of the Aegean Sea area were in the same order as international levels.

235U, 238U, 232Th, 40K and 137Cs activity concentrations in marine sediments along the northern coast of Oman Sea using high-resolution gamma-ray spectrometry

The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine (235)U, (238)U, (232)Th, (40)K and (137)Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of (235)U, (238)U, (232)Th, (40)K and (137)Cs in sediment samples ranged between 1.01 and 2.87 Bq/kg, 11.83 and 22.68 Bq/kg, 10.7 and 25.02 Bq/kg, 222.89 and 535.07 Bq/kg and 0.14 and 2.8 Bq/kg, respectively. The radium equivalent activity was well below the defined limit of 370 Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose.

Distribution of gamma-ray emitting radionuclides in the marine environment of the Burullus Lake: II. Bottom sediments

The sediment compartment has the ability to trap large amounts of radionuclides and to indicate the radiological impact of pollution. The present work shows the results obtained related to the concentrations of 137Cs and natural radionuclides in sediment in the Burullus Lake, Egypt. The average values of 226Ra, 232Th, and 40K in the bottom sediments collected from the east of the Burullus Lake ranged from 10.3 to 21.8 Bq/kg, from 11.9 to 34.4 Bq/kg, and from 268 to 401 Bq/kg, respectively. The study has shown that 40K concentration is nearly uniform throughout the studied area while 226Ra and 232Th are more concentrated in the northeastern shore. Lake sediments showed contamination with 137Cs (2.7-15.9 Bq/kg). The 137Cs sediment activities indicated higher concentrations in the off-shore sites. Concentrations of all γ -ray emitting radionuclides except 40K in water samples were below the detection limits. The 40K sediment-water distribution coefficients of the near-shore samples were higher than the off-shore samples.

Uranium content and dose assessment for sediment and soil samples from the estuarine system of Santos and Sao Vicente, SP, Brazil

In this work, the uranium (U) content in sediment and soil samples collected near the Santos and São Vicente estuaries was determined using the fission track registration technique (SSNTD). The sediment and soil samples after oven-dried and pulverised were prepared in the solution form. About 10 microl of this solution was deposited on a plastic detector and irradiated at the IPEN-IEA-R1 (3.5 MW) nuclear reactor. After the irradiation and chemical etching of the plastic foils, the fission tracks were counted with a system consisting of an optical microscope together with a video camera and a PC. The U content in the analysed samples ranged from 3.12 +/- 0.55 to 18.3 +/- 1.2 ppm for sediments and from 3.21 +/- 0.63 to 11.5 +/- 1.1 ppm for soils or in terms of (238)U equivalent activity from 38.5 +/- 6.8 to 226 +/- 15 and 39.6 +/- 7.8 to 142 +/- 14 Bq kg(-1) for sediments and soils, respectively. These results were compared with other values reported in the literature for sediments and soils collected in environments similar to the ones studied in this work. Most of the values obtained in this work are higher than the world mean and are in reasonable agreement with results found by other authors for sediments and soils from regions considered as polluted or with a high level of radioactivity.

Determination of radioactivity levels and hazards of soil and sediment samples in Fırtına Valley (Rize, Turkey)

The natural radioactivity levels in soil and sediment samples of Firtina Valley have been determined. To our knowledge, there seems to be no information about radioactivity level in the Firtina Valley soils and sediments so far. For this reason, soil and sediment samples were collected along the Firtina Valley and analysis on the collected samples were carried out to determine 238U, 232Th, 40K and 137Cs radioisotopes using high purity germanium detector. The activity concentrations obtained for 226Ra, 214Pb, 214Bi, 228Ac, 208Tl, 40K and 137Cs are given in the unit of Bq/kg. The results have been compared with other radioactivity measurements in different country's soils and sediments. The radium equivalent activity (Raeq), the absorbed dose rate (D), the external hazard index (Hex), the annual gonadal dose equivalent (AGDE) and the annual effective dose equivalent (AEDE) were also calculated and compared with the international recommended values.

The investigation of 137Cs and 90Sr background radiation levels in soil and plant around Tianwan NPP, China

(137)Cs and (90)Sr background levels in soil and plant around Tianwan Nuclear Power Plant (NPP) are reported. Eighty-four soil samples and 44 plant samples were collected from March 2000 to April 2002. The samples were analyzed by gamma spectrometry and radiochemical separation procedure to quantify (137)Cs and (90)Sr radioactivities. The concentrations (Bqkg(-1) dry weight) have been observed in the range of 0.6-1.6 for (90)Sr and 1.4-6.9 for (137)Cs in soils, their average values are 1.0+/-0.3 and 4.6+/-1.6, respectively, which are relatively lower than the reported values in neighboring countries. The mean concentrations (in Bqkg(-1) fresh weight except for tea and grass which is expressed in Bqkg(-1) dry weight) of (137)Cs and (90)Sr are 0.1+/-0.03 and 7.7+/-4.1 in pine needle, 0.27+/-0.05 and 3.0+/-1.1 in tea, 0.65+/-0.19 and 2.1+/-0.3 in grass, 0.033+/-0.021 and 0.084+/-0.045 in wheat, 0.019+/-0.01 and 0.23+/-0.06 in China cabbage, and 0.009+/-0.007 and 0.024+/-0.084 in rice, respectively. The pine needle and tea can be regarded as indicator species for (90)Sr and (137)Cs. The soil-to-plant transfer factor (TF) values of (90)Sr and (137)Cs are, respectively, 0.022 and 0.031 for rice, 0.066 and 3.83 for China cabbage, 0.0088 and 0.089 for wheat, and 0.037 and 0.56 for grass.

Radioactivity concentrations of 40K, 134Cs, 137Cs, 90Sr, 241Am, 238Pu and 239+240Pu radionuclides in Jordanian soil samples

In November 2000, surface and core soil samples were collected from different regions of Jordan. The samples were analyzed by direct gamma spectrometry and combined radiochemical separation procedure to quantify (40)K, (134)Cs, (137)Cs, (90)Sr, (241)Am, (238)Pu and (239+240)Pu radioactivity. Concentrations (Bq.kg(-1) dry weight) have been observed to vary in the range 1.5-2.6 for (134)Cs, 2.8-11.4 for (90)Sr, and 0.13-0.48 for (241)Am, 0.016-0.062 for (238)Pu, 0.28-1.01 for (239+240)Pu and 155-543 for (40)K. The typical concentration of (137)Cs found in topsoils (0-2 cm) ranged in 7.5-576 Bq.kg(-1), dry weight. These values were greater than those observed in samples taken at greater depths (up to 32 cm). Activity ratios of (134)Cs/(137)Cs, (90)Sr/(137)Cs, (239+240)Pu/(137)Cs, (238)Pu/(137)Cs, (241)Am/(137)Cs, (239+240)Pu/(238)Pu and (241)Am /(238)Pu have mean values of 0.0049 (R=1), 0.29 (R=0.76), 0.41 (R=0.90), 0.39 (R=0.85), 0.41 (R=0.88), 7.72 (R=0.97) and 16.66 (R=0.98), respectively. The underlying concentrations were correlated and relatively higher than those reported in neighboring countries. One moss sample, as a biomonitor indicator, was measured and evaluated along with the soil samples. Its data showed higher concentrations of all measured radionuclides due to accumulations over years. The depth distribution of the fission product (137)Cs and the total deposition (Bq.m(-2)) were also studied in selected samples. Estimations of the annual effective dose equivalent due to (137)Cs-soil contamination showed values up to more than 200 microSv.