Levels Of Radionuclides Research Articles

Levels of Cs-137, natural radionuclides and heavy metals in soil of Al-Negila area, Northwestern Coast of Egypt: distribution and risk assessment

ABSTRACT Radionuclides and heavy metals/metalloids content in soils and shore sediments of Al-Negila area (Matrouh, Egypt) were determined to assess the associated environmental risks. A total of 46 soil and shore sediment samples were collected and analysed for natural and man-made radionuclides (238U series, 232Th series, 40K and 137Cs) and heavy metals/metalloids (Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mn, Ni, Si, Sr, Zn, and Hg). Within the study area, the soil and shore sediments are mainly calcareous with sandy, sandy clay and silty clay sized textures. The radionuclides and metals/metalloids concentrations in the soil were higher than those in the shore sediments, meanwhile, they are within the safe world average values. The estimated average (±SD) activity concentrations of 226Ra, 228Ra, 40K and 137Cs were 20.3 ± 5.3, 17.8 ± 6.3, 353.1 ± 129.8, and 2.7 ± 2.7 Bq/kg, respectively. The activity concentration of 137Cs is characterised by the greatest variability characterising the fallout deposited radionuclides. The estimated average values of Raeq (72.9 ± 23.7 Bq/kg), air absorbed gamma dose rate (34.9 ± 11.4 nGy/h), annual effective dose (42.8 ± 14.0 µSv/y), and external hazard index (0.2 ± 0.1) are lower than the international averages reported by UNSCEAR 2008. The average concentrations (mg/kg) of heavy metals/metalloids in soil samples decrease in the following order: Mn (129.8) > Sr (95.0) > Si (28.8) > Ba (25.7) > Zn (25.1) > Cr (17.6) > B (10.0) > Ni (3.9) > Cu (3.3) > Co (0.5) > Cd (0.007) > Hg (7.0 µg/kg). According to the classes of pollution load and contamination degree indices, soils and shore sediments of Al-Negila area are generally uncontaminated. However, a few sampling sites were considered moderately contaminated with B, Cd, and Sr. The radionuclides and heavy metal/metalloid contents in the soil and shore sediments of the area should be observed and assessed regularly, especially for 137Cs.

Risk survey for the population of Recife and neighboring cities due to the occurrence of radium in groundwater

The Metropolitan Region of Recife and its surroundings are heavily exploited to capture water for public supply through tubular wells. However, a survey of the levels of natural radionuclides from these sources had never been carried out, even though part of this region contains a phosphate deposit that has a high concentration of natural uranium. In this context, this research aimed to identify 228Ra and 226Ra levels in groundwater in the coastal region of Pernambuco, Brazil. About 110 points (wells) of drinking water for public supply were identified and studies were carried out to estimate the level of ingestion and subsequent risk due to the presence of this radionuclide. The average concentration of combined radium was 104 mBq.L−1. For 228Ra an effective dose of 0.46, 0.11, 0.12 and 0.0276 mSv.y−1 for infants, children aged 1 and 10 and adults, respectively, were obtained. Although doses above those recommended by WHO were found, the equivalent dose and the induction of bone sarcoma did not indicate a risk to the population. Groundwater with higher dose values is influenced by local geology.

Relationship of 137Cs with Fungal Spore Tracers in the Ambient Aerosols from Fukushima after the 2011 Nuclear Accident, East Japan

Even after 7 years of the nuclear accident that occurred in 2011 at the Fukushima Dai-ichi nuclear power plant (F1NPP), high levels of 137Cs have been detected in ambient aerosols from some polluted areas of Fukushima. Higher levels of radionuclides were often observed in the atmosphere during and after rain events. We presume that biological processes such as fungal activity associated with higher relative humidity may be involved with a possible emission of radioactivity to the atmosphere, which was originally emitted from the F1NPP accident and was deposited over the ground, forest, soil, etc. Here, we report, for the first time, relationships of 137Cs and organic tracers of fungal spores (i.e., arabitol, mannitol and trehalose) in the aerosol samples collected from Fukushima, Japan. Although we found twice-higher concentrations of 137Cs at nighttime than at daytime, fungal spore tracers did not show a consistent trend to 137Cs, that is, organic tracers at nighttime were similar with those at daytime or were even higher in daytime. This study has not clearly demonstrated that fungal spores are the important source of high levels of 137Cs at nighttime. The current unclear relationship is probably associated with the sampling strategy (four consecutive days with a sampling on/off program for day/nighttime samples) taken in this campaign, which may have caused a complicated meteorological situation.

Radiological risk assessment of farm-raised fish species due to natural radionuclides in the freshwater ecosystem of Bangladesh with the statistical approach

We study radiation exposure resulting from the consumption of farm-raised freshwater fish species that form an essential part of the Bangladeshi diet. The levels of radioactivity in the human diet are of particular concern, requiring assessment of possible radiological risks to human health. Therefore, a comprehensive study was carried out to determine the radioactivity levels (226Ra, 228Ra, and 40K) in fifteen commonly available varieties of farm-raised fishes. The gamma-ray spectroscopic analysis showed the presence of radionuclides of 226Ra, 228Ra, and 40K in all studied fishes, but varying degrees. The highest radioactivity levels of 226Ra, 40K, and 228Ra were observed in Rui (Labeo rohita) and Tilapia (Oreochromis mossambicus) with values of 8.50 ± 0.30, 513.28 ± 1.59, and 7.41 ± 0.15 Bqkg−1, respectively. The respective radioactivity levels were lowest in Silver carp (Hypophthalmichthys molitrix), Mola (Amblypharyngodon mola), and Koi (Anabas testudineus) with values of 0.83 ± 0.38, 171.07 ± 1.60, and 0.62 ± 0.30 Bqkg−1. The doses for 226Ra, 228Ra, and 40K due to consumption of a kilogram of farm fish were assessed and range from 5.56 (Sarputi – Puntius sarana) to 54.36 µSvy–1 (Rui – Labeo rohita), 9.77 (Koi – A. testudineus) to 116.79 µSvy–1 (Tilapia – O. mossambicus), and 24.23 (Mola – A. mola) to 72.69 µSvy–1 (Rui – Labeo rohita), respectively. In most cases, the estimated probability of an increase of cancer risk from daily intake of the farm-raised fish diet representing a minor fraction of ICRP values. Statistical analysis shows that the radioactivity and estimated radiological parameters are strongly correlated with 226Ra and 228Ra, while weakly correlated to 40K, suggesting that radiological risk is basically associated and controlled by the activity levels of uranium and thorium series radionuclides.

Evaluation of natural radionuclides distribution in beach sands of Cox’s bazar sea beach, Bangladesh, using multivariate statistical technique

ABSTRACT The distribution of natural series radionuclides 226Ra, 232Th and non-series 40K in the heavy mineral-rich beach sands of highly touristic areas of Cox’s Bazar sea beach has been studied. The study is made to evaluate the gamma radiation exposure to individuals with an aim to establish reference data for the presence of naturally occurring radionuclides. The present study reports the probable first attempt of detail and systematic work in the study areas for estimation of activity concentration in the recent beach sand samples. Radiometric analysis was performed using gamma ray spectroscopy system based on HPGe detector. The mean activity levels of 226Ra, 232Th and 40K in Laboni beach sands were ranged from 255.69±64.57, 336.83±93.96 and 1785.91±89.60 Bq kg-1, respectively. While in Kolatoli beach sands, the respective values were 166.42±35.99, 157.35±35.90 and 1894.42±74.07Bq kg-1, respectively. The mean values of 226Ra and 232Th concentrations in the investigated beach sands were estimated to be very much higher than the corresponding world average values and comparable to those found in high background radiation areas in the world. The heavy minerals seem to control the activity concentrations of 226Ra and 232Th in sand samples, showing some variances based on uranium and thorium bearing minerals. Various radiation health hazard indicators were found to be extremely higher when compared to the recommended values. Hence, heavy mineral-rich sands may pose a significant radiological health risk to the people. The descriptive statistics indicating the radionuclides of 226Ra, 232Th and 40K are uniformly and symmetrically distributed in the Cox’s bazar beach sand. Multivariate statistical analysis showing the radioactivity and estimated radiological parameters are strongly positively correlated with 226Ra and 232Th, while weakly correlated with 40K, signifying that radiological risk is mainly associated and controlled by the radioactivity levels of uranium and thorium series radionuclides.

ACTIVITY LEVEL OF 238U, 232TH, 40K AND RESULTANT DOSE RATES IN SOIL AND SOME COMMON CULTIVATED VEGETABLES

The aim of this present study is to determine the level of natural radionuclides of 40K, 238U and 232Th in soil samples and in (Potato, Solanum tuberosum and Carrot, Daucus carota) samples and vegetables (Tomato, Solanum hycopersicum and Eggplant Solanum melongena) in Al- Mada’in district 30 km southeast of Baghdad, Iraq. High purity germanium (HPGe) detector was used for measurement. The transfer factors, annual absorbed dose rate and the annual effective dose in the samples collected were determined. The results showed that the mean level of measured natural radionuclides were 362.6 ± 41.6 Bqkg-1, 184.7 ± 17.4 Bqkg-1, 191.9 ± 13.5 Bqkg-1, 120.3 ± 10.6 Bqkg-1 and 126.1 ± 11.7 Bqkg-1 for 40K; 19.67 ± 2.00 Bqkg-1, 4.70 ± 0.609 Bqkg-1, 5.43 ± 0.977 Bqkg-1, 3.30 ± 0.460 Bqkg-1 and 2.40 ± 0.701 Bqkg-1 for 238U and 12.34 ± 4.12 Bqkg-1, 3.77 ± 0.904 Bqkg-1, 4.54 ± 0.709 Bqkg-1, 3.51 ± 0.721 and 3.81 ± 0.796 Bqkg-1 for 232Th for soil, tomato, eggplant, potato and carrot samples respectively. The soil-to-tomato transfer factors were found to be 0.512, 0.242 and 0.344 for 40K, 238U and 232Th and soil-to-eggplant transfer factors were found to be 0.534, 0.279 and 0.408 for 40K, 238U and 232Th respectively. The soil-to-potato transfer factors were found to be 0.336, 0.170 and 0.320 for 40K, 238U and 232Th while the soil-to-carrot transfer factors were found to be 0.348, 0.122 and 0.309 for 40K, 238U and 232Th respectively. The mean absorbed dose rate was 30.0 ± 0.57 nGyh-1 and the mean annual outdoor effective dose was 55.2 mSvy-1. The annual effective dose report for this present study 91.6% of the world average value of 70.00 msvy-1 and 87.3% of Thi-Qar government, south Iraq state value of 39.9 msvy-1.

The <i>μ</i>Dose system: determination of environmental dose rates by combined alpha and beta counting – performance tests and practical experiences

Abstract. The μDose system is a recently developed analytical instrument applying a combined α- and β-sensitive scintillation technique for determining the radioactivity arising from the decay chains of 235U, 238U and 232Th as well as from the decay of 40K. The device was designed to meet the particular requirements of trapped charge dating methods and allows the assessment of environmental (i.e. low) levels of natural radionuclides. The μDose system was developed as a piece of low-cost laboratory equipment, but a systematic test of its performance is still pending. For the first time, we present results from a comprehensive performance test based on an inter-laboratory comparison. We compare the results obtained with μDose measurements with those from thick source alpha counting (TSAC), inductively coupled plasma optical emission spectrometry (ICP-OES) and low-level high-resolution gamma spectrometry (HRGS) applied in five participating laboratories. In addition, the reproducibility and accuracy of μDose measurements were tested on certified reference materials distributed by the International Atomic Energy Agency (IAEA; RGU-1, RGTh-1 and RGK-1) and on two loess standards (Nussy and Volkegem) frequently used in trapped charge dating studies. We compare μDose-based results for a total of 47 sediment samples with results previously obtained for these materials by well-established methods of dose rate determination. The investigated natural samples cover a great variety of environments, including fluvial, aeolian, littoral, colluvial and (geo-)archaeological sites originating from high and low mountain regions as well as from lowlands in tropical areas, drylands and mid-latitude zones of Europe, Africa, Australia, Central Asia and the Americas. Our results suggest the μDose system's capability of assessing low-level radionuclide contents with very good accuracy and precision comparable to well-established dosimetry methods. Based on the results of our comparative study and with respect to the practical experiences gained so far, the μDose system appears to be a promising tool for trapped charge dating studies.

RADIOACTIVE CONTAMINATION AND DOSES OF INTERNAL IRRADIATION OF FISH IN THE DEEP LAKE OF THE CHORNOBYL EXCLUSION ZONE

After the accidents at the Chornobyl and Fukushima NPPs, the specific activity of radionuclides in fish in radioactively contaminated reservoirs reached hundreds of kBq kg-1. Over time, as the radiological situation improved, there was a decrease in radioactive contamination of fish, but even now there are cases of exceeding the permissible levels of radionuclides in food. This work aimed to determine in real conditions the content of 90Sr and 137Cs in different species of fish in one of the most radioactively contaminated reservoirs of the Chornobyl Exclusion Zone - Glubokoye lake. As a result of experimental studies conducted from 2016 to 2021, the values of the specific activity of 90Sr and 137Cs in different species of fish were obtained, which were hundreds of times higher than the permissible levels. It is shown that without the use of countermeasures, this situation will persist for several decades. The results show that the internal radiation doses of fish due to the level of their radioactive contamination do not exceed the permissible levels recommended by international organizations for radiation protection of the environment.

Risk Assessment of Natural Radionuclides and Radon Gas in the Artisanal and Small-Scale Gold Mine of Buhemba, Tanzania

Currently, the mining industry in Tanzania faces significant challenges including the presence of radionuclides in the working environment. In this work, different indices were applied to assess the health risk of people living and working in the study area. The radiation hazards in the studied mining areas are compared with the recommended local and international guidelines. The health risk and mitigation measures due to radioactive elements exposure to mine workers and people dwelling in the mines is established. The hyper pure germanium detector (HPGe) was used for radioactivity analysis. The radon gas levels were measured using the Alpha Guard radon monitor. The results on radioactivity; mean effective dose; annual gonadal equivalent and absorbed dose; radium equivalent; internal and external hazard indices; alpha and gamma indices; and the radon gas revealed high values in mining areas compared to the control area. However, some of the levels of radionuclides along with their hazard indices are lower than the recommended international limits. The mitigation measures which include dust suppression using water spray and the use protection gears such as masks and gloves are recommended. The present study recommends follow up and further studies in the ASGM subsector.

Uranium isotopes in groundwater in Ho Chi Minh City and related issues: Health risks, environmental effects, and mitigation methods

Groundwater is regularly used for many purposes, such as drinking and agricultural irrigation systems. Still, it contains high levels of radionuclides (e.g., 238U, 232Th, and 226Ra) that are potentially hazardous to humans and the environment. In this study, activity concentrations of uranium isotopes were analyzed in 15 groundwater samples taken from 15 bored wells in Thu Duc district, Ho Chi Minh City, Vietnam. Environmental effects of the irrigation system with groundwater on agricultural soil in the study area were assessed by models. It was found that the activity concentrations of 238U and 234U in groundwater samples were in the ranges of (13.5–268.7) mBq l−1 and (20.2–438.3) mBq l−1, respectively. The ratio 234U/238U values were ranged from 1.12 to 2, with an average value of 1.44. Based on the model prediction, 25 years irrigation with the groundwater can inject 94.8 Bq both uranium isotopes in 1 kg topsoil. For investigated groundwater samples, the proposed removal method using K2FeO4 removed 74.28% and 81.04% for 234U and 238U, respectively.

Isotopic signatures of plutonium and uranium at Bikar atoll, northern Marshall Islands

We present plutonium (Pu) and uranium (U) isotopic fingerprints (or signatures) in environmental samples collected at Bikar Atoll. Bikar is the second –most northern atoll of the Republic of the Marshall Islands, and therefore an important reference point to evaluate the extension of the regional fallout from the Pacific Proving Grounds (PPG) in Bikini and Enewetak Atolls. Previous studies have shown that regional fallout from atmospheric nuclear weapon testing (NWT) in Bikini and Enewetak has resulted in elevated levels of fallout radionuclides in this atoll. In order to optimally interpret the isotopic fingerprints, we compare our results with data obtained in eleven certified reference materials, representing different contamination sources. As well as 238Pu, 239Pu, 240Pu, 241Pu, 238U and 235U, this study also encompasses less commonly reported radionuclides such as 242Pu, 244Pu and 236U. We show the importance of combining numerous fingerprints for improved assessment of the source of a nuclear contamination.In samples from Bikar, Pu and U isotope ratios were found to vary within narrow ranges. Pu and U fingerprints suggest that regional fallout from the Castle Bravo test in March 1954 was the main source of the contamination. This was further confirmed by two different age dating approaches that estimated 1954 as the year of the contamination. We demonstrate that use of an exponential function to approximate the yield of heavy radionuclides in thermonuclear explosions with increasing mass is a valid approach for estimating the age of a contamination. We show that, if sufficient radionuclide activity concentration measurement results with low uncertainties are available, this method is robust.

Safety and quality of feed for piglets

The results of research on the safety and quality of compound feed of domestic producers for piglets have been presented in the article. The materials for the investigation were 4 samples of the starting complete feed for piglets of main domestic producers. Organoleptic characteristics of compound feed for piglets met the requirements of Federal standard 34109-2017. The assessment of the total bacterial contamination showed that sample No. 3 (the feed plant “VEGA”) has the maximum level of contamination, and the lowest level in sample No. 1 - new feeding technologies plant. The content of toxic elements in compound feed did not exceed their maximum permissible level and met the requirements of Federal standard 34141-2017. The level of radionuclides in compound feed did not exceed their maximum permissible level and corresponded to the standards provided for in the instructions on radiological quality control of feed of the Ministry of Justice No. 831 on 14.04.1995. Thus, the analysis of samples of the starting compound feed of domestic producers for piglets on organoleptic, physic and chemical, bacteriological and sanitary-mycological indicators, for the presence of toxic elements and radionuclides showed that all samples meet the requirements of safety and quality.

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.

Measurement of Activity Concentration Levels of Radionuclides and Assessment of Radiation Hazards for Well Water Samples Collected from Baghdad Governorate, Al-Sadr City, Iraq

In this study, Natural radioactivity levels of water from samples of 10 wells and at different depths 7, 3, and 12 meters were measured with a gamma-ray spectroscopy device using High-Purity Germanium HPGedetector. The samples were collected from different areas of Sadr City, east of Baghdad Governorate. Al-Sadr city is considered as one of the important areas in the capital, Baghdad, due to its population density, which constitutes about 45% of the province’s population. It is very important to assess the radiation risks in these samples because the population still depends on this water in their daily life. The concentration of naturally occurring radionuclides was determined U-238, Th-232, K-40 as all sample’s concentration is higher than the permissible limits according to UNSCEAR 2000. Measurements included the values of natural radioactivity were calculated as the Radium Equivalent Activity Raeq 0.22, External Hazard Index Hex 0.000595, Internal Hazard Index H_in 0.00119, Representative Level were collected The index Iγ 0.001467 and the alpha index I_α 0.0011, the exposure rate Raexp μR/h 0.418, and also calculated the air absorbed dose Dγin nGy/h 0.10164, Dγout nGy/h 0.2024, Dγtotal nGy/h 0.30404, AGED 0.6798, AEDEin 0.000124, AEDE_out 0.000993 and AEDEtotal 0.001117, lifetime cancer risk ELCRout 0.000436, ELCRin 0.003475 and ELCRtotal 0.003911.

Natural radionuclides (NORM) in a Moroccan river affected by former conventional metal mining activities

The main aim of this work was to determine the levels of multiple natural radionuclides in an aquatic system (Moulouya river, Morocco) impacted by multiple abandoned Zinc and Lead mines. 238U, 234U, 232Th, 230Th and 210Po were determined by alpha-particle spectrometry in water and sediment samples collected along the river and in samples from three pit lakes of abandoned mines, located in the Upper Moulouya catchment area. The results enabled the analysis of the different levels of impact of former mining activities, depending on the natural radionuclides. While the activity concentration of U-isotopes in Moulouya river water was slightly elevated in the vicinity of abandoned mine wastes, other natural radionuclides (Th-isotopes and 210Po) levels were typical of a natural environment. This fact is clearly reflected in the magnitude and range observed in the distribution coefficients for the different radionuclides analyzed.

Environmental radioactivity in gold mining in Burkina Faso and potential recycling of mining waste rocks

ABSTRACT Naturally occurring radionuclides have been reported to occur in high concentrations in gold deposits and with other metal ores in Africa. These radionuclides can be released during mining operations and ore processing, causing harmful radiation exposure of mine workers and nearby populations, and may render the mining waste rocks unusable. One large gold mine site in Burkina Faso, near Mana Village, was assessed for naturally occurring radionuclide levels. The area was surveyed for ambient radiation dose rate. Samples from waste rock and sludge from ore milling were analysed by alpha spectrometry, confirming the presence of naturally occurring radionuclides but in relatively low concentrations. It was concluded that mine workers are not exposed to radiation doses significantly above the unmodified natural radiation background. Furthermore, waste rock piles from mining operations can be recycled and used in road construction.

Assessment of residual radionuclide levels at the Bokak and Bikar Atolls in the northern Marshall Islands

The Bikar and Bokak Atolls, located in the northern Marshall Islands, are extremely isolated and consist of pristine marine and terrestrial ecosystems. Both atolls may have experienced significant radioactive deposition following the nuclear weapon testing conducted at Bikini and Enewetak proving grounds. Here we report activity concentrations of artificial radionuclides (239Pu, 240Pu, 241Pu, 241Am, 137Cs and 90Sr) in marine and terrestrial samples collected from Bikar and Bokak Atolls. Artificial radionuclides in soil from the Majuro Atoll are also reported and form a radiological baseline against which the levels at the other atolls can be compared. We observed low levels of artificial radionuclides in soil from Majuro and Bokak, but significantly higher levels in soil from Bikar. The residual radioactivity in the Bikar environment is comparable to the levels previously reported for other nearby atolls, including Taka and Utrik, but lower than for Rongerik, Rongelap, Bikini and Enewetak. An analysis of 240Pu/239Pu isotope ratios and estimations of the dates of contamination from 241Am/241Pu activity ratios both indicated that the Bikar Atoll was contaminated mainly by radioactive fallout from the Castle Bravo test in 1954. We compare the results of our measurements at Bikar and Bokak to data from other atolls in the Marshall Islands and to regions of the world affected by both global and regional fallout from atmospheric nuclear weapons testing and nuclear accidents.

Valorization of rare earth processing byproducts for agriculture usage

Sandy texture soil, a major problem for agriculture requires structure and capacity improvements. However, utilization of soil conditioner may arrest this problem. This research was carried out to investigate the accumulated levels of metal ions and radionuclides in water, soil and plants following phosphogypsum organic (PG organic) added to a sandy soil for 23-month in 3 cropping seasons. The condition in the field was simulated in the laboratory using an open leaching column for 30-day under constant but different pH of leachant. More ions were released at pH < 4.6 and decreases greatly at pH > 5.6. The metal ions measured in the surface and borehole water, and soils were below the target values for respective standard raw drinking water. The metal ions did not accumulate in soil, plant and grain, and water as indicated by biological accumulation coefficients, contamination factors, I-geo index and pollution load index in a sandy soil that received the PG organic. Naturally occurring radionuclide concentrations, such as 226Ra, 228Ra, and 40K, in soil and plant tissue were found to be lower than the average value reported by several earlier studies. Under field condition the pH of water (i.e., rainfall) was greater than pH 5.6, thus renders PG organic became less soluble. There was no leaching of natural occurring radionuclides to the groundwater. Therefore, the application of PG organic to the studied soil had no impact on the soil, plants, and water and suitable as a soil conditioner in sandy texture soils.

Quantifying historical releases and pre-operation levels of metals and radionuclides

Assessing the recovery of aquatic ecosystems from metal and radionuclide contamination requires knowledge of the concentration of radionuclides and metals before anthropogenic releases. Pre-operational conditions, or baseline, are often unknown for many mining operations initiated decades ago. The objectives of this study were to quantify baseline levels of metals and radionuclides and describe historical releases of an industrialised watershed in Northern Ontario where mining operations were carried out from 1955 to 1996. For this purpose, water and surface sediment samples were collected from this watershed and in an adjacent non-industrialised watershed every 2 km. Using metal and radionuclide concentrations in the non-impacted watershed, we calculated water and sediment baseline concentrations as upper 95th percentile values. Baseline pH, 226Ra and uranium in water of lakes and rivers were similar at pH of 6.8, 10 mBq·l−1, and 2.5 μg·l−1, respectively. For sediments, baseline lake sediment exhibited concentrations of radionuclides that were higher than river sediments. We calculated baseline concentrations in lake sediment at 2,115 Bq·kg−1 210Pb, 535 Bq·kg−1 210Po, 218 Bq·kg−1 226Ra, 235 Bq· kg−1 228Th, 184 Bq·kg−1 230Th, and 223 Bq·kg−1 232Th. Baseline concentrations of metal levels in lakes were at 98 mg kg−1 Ni, 119 mg kg−1 Cu, 2300 mg kg−1 Zn, 112 mg kg−1 Pb and 19 mg kg−1 U. In Lake Huron, we collected two sediment core profiles along with surface sediment to estimate baseline radionuclide activities and metal concentrations and quantify historical releases from the industrialised watershed. The sediment core profiles reflected baseline conditions prior to releases from the uranium mining operation and contamination from its onset in 1955 to its closure in 1996. Concentration of metals in pre-industrial sediment layers were lower than in surface sediment of Lake Huron, suggesting atmospheric depositions. Our study indicates that collecting surface sediment in this non-impacted watershed may yield baseline concentrations for uranium and radionuclides. For metal, collecting surface sediment may yield ambient metal concentrations because of long-range atmospheric transport from remote sources. By comparison, sedimentary profiles can provide baseline concentrations of both metals and radionuclides. In the case of the Serpent River watershed, we report that water quality has recovered downstream of Quirke Lake as of 1993 and that additional sediment cores would better assess sediment recovery.

Fate of anthropogenic radionuclides (90Sr, 137Cs, 238Pu, 239Pu, 240Pu, 241Am) in seawater in the northern Benguela upwelling system off Namibia

A baseline study on anthropogenic radioactivity in the Namibian marine ecosystem, which is part of the northern Benguela upwelling system, known as one of the most productive ocean areas in the world, has been performed. A scientific cruise carried out in 2014 covering inshore and offshore areas, exhibiting different oceanographic features, has provided a basis for better understanding the distributions, ratios and inventories of six anthropogenic radionuclides (90Sr, 137Cs, 238Pu, 239Pu, 240Pu and 241Am) in seawater. Although 3H was also measured, due to extremely low levels, its behaviour was not studied. The main source of 90Sr, 137Cs, 239Pu, 240Pu and 241Am in the samples analysed was proven to be global fallout, a finding further confirmed by 240Pu/239Pu and 90Sr/137Cs ratios. Furthermore, the 238Pu SNAP-9A satellite accident signal was confirmed once again through the determination of the 238Pu/239+240Pu activity ratio. Inshore and offshore samples showed different patterns due to the unique oceanographic features of this upwelling system. The levels of anthropogenic radionuclides, comprehensively assessed for the first time in this region, are comparable with the few existing data and filled a critical gap for the Southern Atlantic Ocean.