It is well known that George Hevesy and Hilde Levi were the original discoverers of neutron activation analysis. However, there were many other researchers in Europe that firstly unknowingly and ...knowingly discovered the neutron, and others who experimented in neutron induced radioactivity. A historical timeline of the several parallel experiments in a very short period is given in this synopsis. It eventually was Hevesy and Hilde to first use the powerful technique of neutron activation analysis for analytical chemistry.
•Unknowingly and knowingly first discoveries of the neutron.•Neutron induced radioactivity.•Neutron activation analysis.
Uranium (U) has been released to surface soil and groundwater through military and industrial activities. Soluble forms of U transferred to drinking water sources and food supplements can potentially ...threaten humans and the biosphere due to its chemical toxicity and radioactivity. The immobilization of aqueous U onto iron-based minerals is one of the most vital geochemical processes controlling the transport of U. As a consequence, much research has been focused on the use of iron-based materials for the treatment of U contaminated waters. One material currently being tested is nanoscale zero-valent iron (nZVI). However, understanding the removal mechanism of U onto nZVI is crucial to develop new technologies for contaminated water resources. This review article aims to provide information on the removal mechanism of U onto nZVI under different conditions (pH, U concentration, solution ion strength, humic acid, presence of O2 and CO2, microorganism effect) pertinent to environmental and engineered systems, and to provide risk or performance assessment results with the stability of nZVI products after removal of U in environmental restoration.
•Soluble uranium removal by zero valent iron in freshwater and waste water.•Environmental restoration of uranium contaminated water.•Zero valent iron nanoparticles used for environmental remediation.
Self-attenuation correction factors were experimentally determined using radioactive point sources in combination with a subject material of naturally occurring radioactive material (NORM) obtained ...from oil exploration waste products. The self-attenuation correction factors were taken across a range of gamma ray energies from 41.73 to 1408.0keV. It is noted that the greatest amount of self-attenuation occurs in the energy regime below 200keV and rises to near zero attenuation at higher energies for these types of samples. For the 46.5keV gamma ray of 210Pb there can be an underestimation of 62%.
•Self attenuation of gamma-rays.•Naturally occurring radioactive material in oil and gas industry.•Ra-226, Ra-228 and Pb-210.
Observations from 1980 to 2013 of 20 aerosol constituents, ozone and mercury at Alert, Canada (82.50°N, 62.35°W), were analyzed for trends and dominant factors of the Arctic haze during winter and ...spring. Trends reflect changing emissions in Eurasia, the main source region for surface pollution in the high Arctic. SO42−, H+, NH4+, K+, Cu, Ni, Pb, Zn, nonsoil V, nonsoil Mn, and equivalent black carbon decreased between 23% and 80% as emissions declined rapidly in northern Eurasia during the early 1990s. NO3− increased by 20% as aerosol acidity declined. Metals were linked to emissions from smelting and fossil fuel combustion. In winter, ozone increased by 5% over 23 years, consistent with other observations and global modeling. Twelve PMF factors emerged for the dark period (November to February) and 13 for the light period (March to May). Eleven PMF factors are common to both dark and light, a twelfth factor was associated with sulfate in the dark and nitrate in the light, and the thirteenth (light period) was related to ozone and gaseous mercury depletion near Alert. IODINE and NITRATE factors, important for Arctic chemistry, changed with sunlight. In the light, 50% of all NO3− was on the NITRATE factor, while in the dark, most was associated with MODIFIED SEA SALT and equivalent black carbon. In the dark (light), 90% (28%) of iodine were found on the factor IODINE and 58% associated with SEA‐SALT and MODIFIED SEA‐SALT. These results help in understanding the role of atmospheric chemistry in weather and climate processes.
Key Points
Over 34 years, aerosol pollution constituents at Alert Canada decreased between 28% and 80% including black carbon decline at 52%; nitrate, sodium, and chloride concentrations increased between 19% and 43%, whereas ozone increased by 5%
A positive matrix factor analysis contrasting dark and sunlit periods revealed information on sources and aerosol chemistry processes
Twelve (dark period) to 13 (sunlit period) aerosol and gas factors yielded information on sources and/or physical and chemical processes that allowed for better interpretation of observed trends
In this study, nanoscale zero valent iron I-NZVI was investigated as a remediation strategy for uranium contaminated groundwater from the former Cimarron Fuel Fabrication Site in Oklahoma, USA. The ...1 L batch-treatment system was applied in the study. The result shows that 99.9% of uranium in groundwater was removed by I-NZVI within 2 h. Uranium concentration in the groundwater stayed around 27 μg/L, and there was no sign of uranium release into groundwater after seven days of reaction time. Meanwhile the release of iron was significantly decreased compared to NZVI which can reduce the treatment impact on the water environment. To study the influence of background pH of the treatment system on removal efficiency of uranium, the groundwater was adjusted from pH 2–10 before the addition of I-NZVI. The pH of the groundwater was from 2.1 to 10.7 after treatment. The removal efficiency of uranium achieved a maximum in neutral pH of groundwater. The desorption of uranium on the residual solid phase after treatment was investigated in order to discuss the stability of uranium on residual solids. After 2 h of leaching, 0.07% of the total uranium on residual solid phase was leached out in a HNO3 leaching solution with a pH of 4.03. The concentration of uranium in the acid leachate was under 3.2 μg/L which is below the EPA's maximum contaminant level of 30 μg/L. Otherwise, the concentration of uranium was negligible in distilled water leaching solution (pH = 6.44) and NaOH leaching solution (pH = 8.52). A desorption study shows that an acceptable amount of uranium on the residuals can be released into water system under strong acid conditions in short terms. For long term disposal management of the residual solids, the leachate needs to be monitored and treated before discharge into a hazardous landfill or the water system. For the first time, I-NZVI was applied for the treatment of uranium contaminated groundwater. These results provide proof that I-NZVI has improved performance compared to NZVI and is a promising technology for the restoration of complex uranium contaminated water resources.
•Soluble uranium removal by zero valent iron groundwater from nuclear fabrication facility.•Environmental restoration of uranium contaminated water.•Zero valent iron nanoparticles used for environmental remediation.
The naturally occurring radionuclides of (235)U, (238)U and (232)Th and their daughter products are a potential major source of anthropogenic radiation to tobacco smokers. Often overlooked is the ...presence of (40)K in tobacco and its implication to radiation dose accumulation in the human body. In this study, these three radiation sources have been determined in four typical US cigarettes using neutron activation analysis (NAA). The NAA reactions of (238)U(n,γ)(239)U, (232)Th(n,γ)(233)Th and (41)K(n,γ)(42)K were used to determine (235)U, (238)U and (232)Th and (40)K, respectively. The activity of (238)U can easily be determined by epithermal NAA of the (238)U(n,γ)(239)U reaction, and the activity of (235, 234)U can easily be deduced. Using isotopic ratios, the activity due to (40)K was found by the determined concentrations of (41)K (also by epithermal neutrons) in the bulk material. Each gram of total potassium yields 30 Bq of (40)K. The annual effective dose for smokers using 20 cigarettes per day was calculate to be 14.6, 137 and 9 μSv y(-1) for (238,235,) (234)U, (232)Th and (40)K, respectively. These values are significantly lower that the dose received from (210)Po except for (232)Th.
We have described the determination of uranium in environmental, geological, and agricultural specimens by three different non-destructive nuclear methods. The effectiveness, as defined as the lower ...limits of detection in this work, of quantifying trace levels of bulk uranium in geological samples was evaluated for several common NAA techniques. These techniques include short-lived and medium-lived neutron activation analysis using thermal and epithermal neutrons; these results were compared with an assessment of Compton suppressed gamma-ray counting. A careful evaluation of three major (n,γ) reactions with chlorine, manganese and sodium that could impede determining low levels of uranium due to high Compton continuums was done. The evaluation of Compton suppressed passive gamma counting revealed that uranium concentrations below 50 mg kg−1 were not adequate to achieve good counting statistics using the 234mPa the second daughter product of 238U.
► Determination of uranium concentrations in geological, environmental, and agricultural specimens. ► Use of several NAA and passive counting methods. ► Identified several key interferences. ► Use of Compton suppression to minimize effects of interferences.
Elevated concentrations of sodium (Nasuperscript +) and chloride (Clsuperscript -) in surface and ground water are common in the United States and other countries, and can serve as indicators of, or ...may constitute, a water quality problem. We have characterized the most prevalent natural and anthropogenic sources of Nasuperscript + and Clsuperscript - in ground water, primarily in Illinois, and explored techniques that could be used to identify their source. We considered seven potential sources that included agricultural chemicals, septic effluent, animal waste, municipal landfill leachate, sea water, basin brines, and road deicers. The halides Clsuperscript -, bromide (Brsuperscript -), and iodide (Isuperscript -) were useful indicators of the sources of Nasuperscript +-Clsuperscript - contamination. Iodide enrichment (relative to Clsuperscript -) was greatest in precipitation, followed by uncontaminated soil water and ground water, and landfill leachate. The mass ratios of the halides among themselves, with total nitrogen (N), and with Nasuperscript + provided diagnostic methods for graphically distinguishing among sources of Nasuperscript + and Clsuperscript - in contaminated water. Cl/Br ratios relative to Clsuperscript - revealed a clear, although overlapping, separation of sample groups. Samples of landfill leachate and ground water known to be contaminated by leachate were enriched in Isuperscript - and Brsuperscript -; this provided an excellent fingerprint for identifying leachate contamination. In addition, total N, when plotted against Cl/Br ratios, successfully separated water contaminated by road salt from water contaminated by other sources.
The naturally occurring radionuclides of super(235)U, super(238)U and super(232)Th and their daughter products are a potential major source of anthropogenic radiation to tobacco smokers. Often ...overlooked is the presence of super(40)K in tobacco and its implication to radiation dose accumulation in the human body. In this study, these three radiation sources have been determined in four typical US cigarettes using neutron activation analysis (NAA). The NAA reactions of super(238)U(n, gamma ) super(239)U, super(232)Th(n, gamma ) super(233)Th and super(41)K(n, gamma ) super(42)K were used to determine super(235)U, super(238)U and super(232)Th and super(40)K, respectively. The activity of super(238)U can easily be determined by epithermal NAA of the super(238)U(n, gamma ) super(239)U reaction, and the activity of super(235, 234)U can easily be deduced. Using isotopic ratios, the activity due to super(40)K was found by the determined concentrations of super(41)K (also by epithermal neutrons) in the bulk material. Each gram of total potassium yields 30 Bq of super(40)K. The annual effective dose for smokers using 20 cigarettes per day was calculate to be 14.6, 137 and 9 mu Sv y super(-1) for super(238,235,234)U, super(232)Th and super(40)K, respectively. These values are significantly lower that the dose received from super(210)Po except for super(232)Th.
Neutron activation analysis is a useful analytical technique for the determination of many nuclides. However, the resulting gamma-ray spectra frequently have overlapping photopeaks, necessitating ...complicated peak de-convolution techniques to perform an accurate measurement. This work investigates the viability of gamma–gamma coincidence measurements of neutron activation analysis samples for the determination of
76
As,
160
Tb, and
169
Yb to improve peak de-convolution and significantly lower the background. It is shown that these nuclides can be better determined using gamma–gamma coincidence measurements as opposed to single detector measurements. Comparisons are shown between the single channel and coincidence-gated spectra to demonstrate the de-convolution improvements achieved with coincidence gating. Additionally, a quality assurance protocol has been developed using
226
Ra and
152
Eu to ascertain that the coincidence electronics are set up properly. This protocol quantitatively demonstrates the capability of this system to discriminate between true coincidence and noncoincident events.
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