Assessment of contamination of natural and anthropogenic radionuclides in rice samples collected from Songkhla province, Thailand

Study on assessment of contamination of natural and artificial radionuclides in agricultural products samples are very important to all human being as a consumer. In the present study, we have measured and evaluated the specific activities of natural (40K, 226Ra and 232Th) and anthropogenic (137Cs) radionuclide in rice samples. The 30 rice samples were collected from general and department stores at Songkhla province in the south of Thailand. The high-purity germanium (HPGe) detector and gamma-ray spectrometry analysis system which was set-up in advanced laboratory in Thailand Institute of Nuclear Technology (public Organization) or TINT were employed to perform all of measurements and analysis for this study. The frequency distribution of specific activities of 40K, 226Ra, 232Th and 137Cs for this study were also studied and found to be asymmetrical distribution with the skewness of 1.29, 1.43, 2.32 and 0.82, respectively. For this reason, the median values of specific activities of 40K, 226Ra and 232Th which were 620.04 ± 44.30, 3.73 ±0.54 and 2.44 ±0.54 Bq/kg respectively, should be selected and also used to calculate some related radiological hazard indices in this study. Furthermore, the excess lifetime cancer risk (ELCR) would be also evaluated and presented. Moreover, the results of present study were taken to compare with some data and studies in Thailand and global measurement and calculations. It was found that the outcomes satisfied the standards of UNSCEAR and IAEA.

Radiological hazard assessments of radionuclides in building materials, soils and sands from the Gaza Strip and the north of Sinai Peninsula

Radiological hazards to the residents of the Gaza Strip, Palestine and the north of the Sinai Peninsula, Egypt, were determined using the naturally occurring radionuclides (226Ra, 232Th and 40K) in 69 samples of building materials (demolition debris, plasters, concretes, from recycling plants and raw cements from suppliers), soils and sands collected in the field. The radiological hazard indices and dose rates calculated with the activity concentrations of radionuclides in those materials determined by gamma-ray spectrometry indicate that the values are all within the global limits recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation 2000 and European Commission 1999. The results of Spearman's correlation and hierarchical cluster analysis for 210Pb in the building materials, soils and sands suggest that the samples include 210Pb from the atmospheric fallout. The medium correlation between 232Th and 40K in demolition debris implies that their activity concentrations are characteristic of the building materials and constituents of the demolition debris. Non-natural ratio of 238U/235U was found in the soil and sand samples collected in the Gaza Strip. Furthermore, 137Cs and 241Am were detected in some soil, sand and demolition debris samples analyzed in this study. The origins of those anthropogenic radionuclides were considered.

Radioecological and geochemical peculiarities of cryoconite on Novaya Zemlya glaciers

In recent years, cryoconite has received growing attention from a radioecological point of view, since several studies have shown that this material is extremely efficient in accumulating natural and anthropogenic radionuclides. The Novaya Zemlya Archipelago (Russian Arctic) hosts the second largest glacial system in the Arctic. From 1957 to 1962, numerous atmospheric nuclear explosions were conducted at Novaya Zemlya, but to date, very little is known about the radioecology of its ice cap. Analysis of radionuclides and other chemical elements in cryoconite holes on Nalli Glacier reveals the presence of two main zones at different altitudes that present different radiological features. The first zone is 130–210 m above sea level (a.s.l.), has low radioactivity, high concentrations of lithophile elements and a chalcophile content close to that of upper continental crust clarkes. The second zone (220–370 m a.s.l.) is characterized by high activity levels of radionuclides and “inversion” of geochemical behaviour with lower concentrations of lithophiles and higher chalcophiles. In the upper part of this zone (350–370 m a.s.l.), 137Cs activity reaches the record levels for Arctic cryoconite (5700–8100 Bq/kg). High levels of Sn, Sb, Bi and Ag, significantly exceeding those of upper continental crust clarkes, also appear here. We suggest that a buried layer of contaminated ice that formed during atmospheric nuclear tests serves as a local secondary source of radionuclide contamination. Its melting is responsible for the formation of this zone.

Distribution of some natural and anthropogenic radionuclides in the sediments and seawater along the coastal areas of North Sulawesi

Studies on the radionuclide distribution of some naturally occurring radioactive materials (NORM) and anthropogenic radionuclides in the sediments of the coastal areas of North Sulawesi were conducted to provide baseline data for the effective monitoring of radioactive fallout in these areas. Sediment samples were collected by a van Veen grab samples about 100 – 300 m from the shoreline, and 60 L of seawater was pre-concentration to precipitated 137Cs. Activity concentration of the three main natural radionuclides (222Ra, 232Th, and 40K) and 137Cs were determined using a high-resolution HPGe gamma-spectroscopy system and presenting background about the radiological levels and assessing the associated hazards. The activity of 226Ra ranged from 2.1 to 9.5 Bq kg−1 with an average value of 5.9 Bq kg−1. The activity of 232Th varies from 2.4 to 10.4 Bq kg−1 with an average value of 5.2 Bq kg−1. The 40K ranges between 169.1 to 492.7 Bq kg−1 with an average value of 238.8 Bq kg−1. The average activity concentration of 40K (238.8 Bq kg−1) in the sediment samples was lower than the worldwide average concentration (420 Bq kg−1). The current level of activity 137Cs varied from 0.05 to 0.40 Bq kg−1 in sediment samples and 0.98 to 1.33 Bq m−3 in seawater samples. 134Cs in all samples were not detected or below the detection limit. This fact indicated that radioactive cesium in Celebes Sea areas of North Sulawesi still originated from global fallout and insignificant influenced by the FDNPP accident. All radionuclide radiation values in the recent study are lower than the world average. Therefore, the potential danger of radiation generated from the surrounding environment has not yet caused a radiological health impact for the people living on the coast of North Sulawesi. Natural and artificial radionuclide activity data in this study will be used as the basis for sedimentary activity along the coast of North Sulawesi.

NATURAL RADIATION ABSORBED DOSE RATE AND RADIATION TRANSFER FACTOR FROM SOIL TO VEGETABLE IN SOME SELECTED AREAS OF CHITTAGONG, BANGLADESH

The study aimed to investigate natural radioactivity levels and Transfer Factors of natural radionuclides from soil to some plants in Chittagong, Bangladesh. The concentrations of naturally occurring and anthropogenic radionuclides in soil and plants were measured in this work to determine the absorbed dose rate and the transfer factors of radionuclides from soil to plant. Plants (Spinach and Vegetables) and corresponding soil samples were collected from three different locations in Chittagong (Nasirabad, Sitakunda, and Halda Agrotechnology), and the concentrations of activity of natural radionuclides were measured using gamma-ray spectrometry. The average absorbed dose rate in the soil of Nasirabad, Sitakunda, and Halda Agrotechnology are 49.84 nGyh-1, 37.4 nGyh-1, and 45.6 nGyh-1. The average transfer factor from soil to plants, recorded for 238U, 232Th, and 40K of these study areas, are 0.461, 0.400, and 3.10, respectively. The ratio of soil to plant transfer factor for the present study compared with some previous work. The Transfer Factor of 40K gives some high value but does not exceed the limit of the different published values. Because there are no existing databases for the natural radioactivity in soil and plants from Chittagong, Bangladesh, our results are establishing a database for the Chittagong, Bangladesh soil and plants. This data may be used as a database for further investigation for the betterment of public health.

The burned area extracting in Chernobyl Exclusion Zone using Random Forest

<p>The Chernobyl Nuclear Power Plant (CNPP) accident that happened in 1986 is the largest source of anthropogenic radionuclides released into the environment in history. In recent 20 years, the climate and land-use changes have increased the frequency of large forest fires in and around the Chernobyl Exclusion Zone. It is critical to extract the burned areas accurately because they are the basis to estimate the biomass burning emission and then analyze the second diffusion of radioactive residue released from the CNPP accident. In this study, we established a burned area extracting method based on the random forest (RF) algorithm using the Moderate Resolution Imaging Spectroradiometer (MODIS) MOD09GA / MYD09GA and LANDSAT -7 ETM+ /-8 OLI images. The field observation in 2015 and MODIS MOD14A1 (thermal anomaly data) product were adopted to generate sampling points for RF. The reflectance difference spectroscopy of near-infrared band and difference in vegetation indices (NDVI, NBR, NDWI) between pre- and post-fire imagery were used as input data for the RF classifier. Subsequently, the historical burned area in 2015 and 2020 were detected using the trained RF classifier. The preliminary results of the identified burned area show good consistency with the MODIS MCD64A1.006 product of NASA and FireCCI51product of ESA. It should be noted that our RF algorithm can even detect the relatively small fire scars compared to the two existing products due to the usage of high-resolution LANDSAT image.</p><p> </p>

Annual variability of the long-lived anthropogenic radionuclides 129I and 236U in the Fram Strait and their use as water mass composition tracers

<p>Anthropogenic chemical tracers are powerful tools to study pathways, water mass provenance and mixing processes in the ocean. Releases of the long-lived anthropogenic radionuclides <sup>129</sup>I and <sup>236</sup>U from European nuclear reprocessing plants label Atlantic Water entering the Arctic Ocean with a distinct signal that can be used to track pathways and timescales of Atlantic Water circulation in the Arctic Ocean and Fram Strait. Apart from their application as transient tracers, the difference in anthropogenic radionuclide concentrations between Atlantic- and Pacific-origin water provides an instrument to distinguish the interface between both water masses. In contrast to classically used water mass tracers such as nitrate-phosphate (N:P) ratios, the two radionuclides are considered to behave conservatively in seawater and are not affected by biogeochemical processes occurring in particular in the broad shelf regions of the Arctic Ocean.</p><p>Here we present a time-series of <sup>129</sup>I and <sup>236</sup>U data across the Fram Strait, collected in 2016 (as part of the GEOTRACES program) and in 2018 and 2019 (by the Norwegian Polar Institute). While the overall spatial distribution of both radionuclides was similar among the three sampling years, significant differences were observed in the upper water column of the EGC, especially between 2016 and 2018. This study is the first attempt to investigate the potential of <sup>129</sup>I and <sup>236</sup>U as water mass composition tracers in the East Greenland Current (EGC). We discuss how the <sup>129</sup>I - <sup>236</sup>U tracer pair can be applied to estimate fractions of Atlantic and Pacific Water, especially considering their time-dependent input into the Arctic Ocean.</p>