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1.
Concentrations levels of uranium and thorium isotopes have been analyzed in the m mineral spring waters of a high background region of Brazil: Poços de Caldas and Águas da Prata. The procedure was based on the determination of238U,234U,232Th,230Th and228Th by -spectrometry after separation and purification of the isotopes of interest by using anion-exchange chromatography and preparation of the samples for -measurements by electrodeposition. The concentration varied from <1.1 to 28.4 mBq.l–1 and from <1.6 to 141 mBq.l–1 for238U and234U, respectively. Thorium isotope measurements varied from <0.2 to 1.8 mBq.l–1 from <0.3 to 4.9 mBq.l–1 and from <0.8 to 19.9 mBq.l–1 for232Th,230Th and228Th, respectively. Calculations of thorium and uranium isotopic activity ratios were carried out giving values ranging from 1.9 to 7.2, from 1.2 to 3.0 and from 7.7 to 15.3 for234U/238U,230Th/232Th and228Th/232Th, respectively. The effective doses due to the intake of238U and234U present in these waters are expected to reach values up to 1.4×10–3 mSv y–1 and 8.0×10–3 mSv y–1, respectively.  相似文献   

2.
Measurements of some selected radionuclides were carried out in rain waters collected from Ibaraki Prefecture, Japan, following the nuclear accident at Tomsk-7, Russian Federation, in April 1993. The concentrations obtained for artificial radionuclides were90Sr1.8 mBq l–1,137Cs0.1 Bq l–1,131I0.1 Bq l–1 and129I4 Bq l–1. Uranium (238U) concentrations in rainfalls in April 1993 were 6.3–39 ng l–1. These data were compared to control values obtained previously and there was no appreciable influence on the radioactivity levels in Japan after the Tomsk-7 accident. Since only limited data on the concentrations of129I and uranium in rain water are available, these new analytical results contribute to understanding the background levels for these nuclides.  相似文献   

3.
A chemical procedure for transferring deposited solid matter from a cellulose filter into the liquid scintillation cocktail has been described. The influence of chemical and color quenching on alpha and beta detection efficiency, as well as on misclassification of beta and alpha pulses was corrected by an external standard method. Under the chosen pulse shape discrimination level (PSD), the alpha and beta detection efficiencies were above 85% and spillovers of alpha and beta pulses were below 10% and 2% respectively. Determination limits for samples containing up to 200 mg of mineral matter were 0.015 mBq m–3 for alpha, 0.055 mBq.m–3 for210Pb and 0.055 mBq.m–3 for beta activity (counting time 12000 s and volume of filtered air 1000 m3). The method has been applied for routine monitoring of210Pb as well as for gross alpha and beta activities of longer-living radionuclides (T1/2.>11 hrs) in suspended air matter.  相似文献   

4.
A method in which222Rn is extracted from 0.5 1 water samples to 20 ml toluene is described. 10 ml toluene solution with extracted222Rn is directly added to a glass scintillation vial containing 10 ml of liquid naphthalene based scintillation cocktail. Apart from diluting by toluene, the final counting solution still has excellent properties in terms of: / separation by pulse shape analysis, detection efficiency and background in the -region. The detection limit of222Rn for 0.5 1 water samples was 1.5 mBq l–1 (for 12,000 s count time). The concentration of222Rn in different environmental samples such as rain, tap and mineral waters as well as deep well waters were determined.  相似文献   

5.
Concentrations of99Tc were determined by inductively coupled plasma mass spectrometry (ICP-MS) on coastal seawater in the general environment in Japan. Technetium was enriched on iron hydroxide by repetitive co-precipitation method from a large volume of seawater and separated from impurities by solvent extraction and ion-exchange techniques. The concentrations of99Tc were 1.0 to 7.4 Bq1–1, which was one order of magnitude lower than the level reported on seawater from general environment by beta-ray counting. Concentrations of137Cs determined on the same seawater were 3.7 and 3.9 mBq1–1. The activity ratio of99Tc/137Cs was calculated to be 2.7×10–4. This ratio was very close to the value expected for fallout from nuclear tests.  相似文献   

6.
Helium-3 (3He) mass spectrometry for the analysis of low-level tritium (3H) concentrations (0.5 to 5 Bq·l–1) in environmental sample matrices was compared with conventional low-level -decay counting methods. The mass-spectrometry method compared favorably, equalling or surpassing conventional decay-counting methods with respect to most criteria. Additional research and method refinements may make3He mass spectrometry the method of choice for routine, low-level to very-low-level (L<0.5 Bq·l–1)3H measurements in a wide variety of environmental samples in the future.  相似文献   

7.
A relatively simple method has been developed for the determination of210Pb via its -emitting daughter,210Bi. Lead-210 was separated from interfering elements as lead sulphate. The precipitate was dissolved in an alkaline solution of EDTA and the Cerenkov signal produced by the build-up of210Bi was counted 30 days after storage using tritium channel of a liquid scintillation counter. Cerenkov counting efficiency was found to be approximately 20%. A lower limit of detection of 5.1 mBq/1 (based on 3 of the background with 500 minute counting time) was achieved. Chemical recoveries in the range of 70–100% were determined gravimetrically. Interference associated with currently used methods is avoided. Data from from both spiked samples and natural samples are presented.  相似文献   

8.
Some modifications of the stannous chloride reduction method for the estimation of inorganic phosphate reported by Berenblum-Chain are suggested. By this method, it is possible to measure 25 g l–1 of phosphorus /P/ as inorganic phosphate in the presence of macromolecules like deoxyribonucleic acid /100 g ml–1/, as compared to 200 g l–1 of P by the original method. If a larger sample volume /30 ml/ is used, even 5 g l–1 of P can be measured.  相似文献   

9.
99Tc a pure -particle emitter with long half-life (T=2.13×105 y) was measured in Rhône river water and in Mediterranean sea water near the river mouth. The values obtained in the Rhône river allowed us to show the downstream distribution of the effluents from the nuclear fuel reprocessing plant of Marcoule: the99Tc activity which is low above the plant, 0.016 mBq 1–1, is 0.4 mBq 1–1 at Roquemaure, located 14 km below the plant, and then decreases as a function of distance from the plant.  相似文献   

10.
The concentrations of238Pu and239, 240Pu were determined in 12 sediment samples collected from the bed of the Romanian Danube river and Black Sea coast during June–September 1994. After the sample material has been properly prepared and242Pu tracer added, plutonium was separated from americium and curium by anion exchange. After electrodeposition on stainless steel discs the elements were counted with an -spectrometry system with silicon surface-barrier detectors. The239, 240Pu concentrations range between 150 and 800 mBq kg–1 dry, while the238Pu concentrations rise up to max 150 mBq kg–1 dry. Although the chemical yields are rather low (51%) we appreciate the results as valuable since they report for the first time the distribution of the plutonium contamination along the Danube river and the Black Sea coast-Romanian sector.  相似文献   

11.
In this paper, a novel flow injection chemiluminescence (CL) determination of l-cysteine is proposed. The method is based on the CL reaction of l-cysteine and KBrO3 in acidic medium. The CL intensity was greatly enhanced in the presence of quinine. The CL intensity was linear with l-cysteine concentration in the range of 0.2–80 g L–1, and the detection limit was 0.1 g L–1 (3). A complete analysis, including sampling and injecting, could be performed in 1 min, giving a throughput of about 60 h–1. The relative standard deviation was 1.6% for 0.8 g L–1 l-cysteine (n=11). The proposed method was satisfactorily applied to the determination of cysteine in an amino acid mixture and human urine. The mechanism of the CL reaction is also discussed.  相似文献   

12.
The development of a fluorimetric method for the determination of zinc, based on the fluorescence of the zinc-8-(benzenesulphonamido) quinoline chelate in a micellar medium of sodium dodecylsulfate, is reported. The detection limit is 0.2 g l–1, the working range is 0.5–700 g l–1, and the sample throughput is 145 h–1. The method was evaluated for the determination of zinc in food samples.A batch procedure for the simultaneous determination of zinc and cadmium, based on the synchronous and derivative spectra, is also proposed.  相似文献   

13.
The methods available for determination of environmental contamination by plutonium at ultra-trace levels require labor-consuming sample preparation including matrix removal and plutonium extraction in both nuclear spectroscopy and mass spectrometry. In this work, laser-ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) was applied for direct analysis of Pu in soil and sediment samples. Application of a LINA-Spark-Atomizer system (a modified laser ablation system providing high ablation rates) coupled with a sector-field ICP–MS resulted in detection limits as low as 3×10–13 g g–1 for Pu isotopes in soil samples containing uranium at a concentration of a few g g–1. The isotope dilution (ID) technique was used for quantification, which compensated for matrix effects in LA–ICP–MS. Interferences by UH+ and PbO2+ ions and by the peak tail of 238U+ ions were reduced or separated by use of dry plasma conditions and a mass resolution of 4000, respectively. No other effects affecting measurement accuracy, except sample inhomogeneity, were revealed. Comparison of results obtained for three contaminated soil samples by use of -spectrometry, ICP–MS with sample decomposition, and LA–ICP–IDMS showed, in general, satisfactory agreement of the different methods. The specific activity of 239+240Pu (9.8±3.0 mBq g–1) calculated from LA–ICP–IDMS analysis of SRM NIST 4357 coincided well with the certified value of 10.4±0.2 mBq g–1. However, the precision of LA–ICP–MS for determination of plutonium in inhomogeneous samples, i.e. if "hot" particles are present, is limited. As far as we are aware this paper reports the lowest detection limits and element concentrations yet measured in direct LA–ICP–MS analysis of environmental samples.Sergei F. Boulyga is on leave from The Radiation Physics and Chemistry Problems Institute, 220109 Sosny, Minsk, Belarus.  相似文献   

14.
Summary Sulphate in various environmental samples was determined by measuring the optical absorbance upon reaction with the barium(II) dimethylsulphonazo(III) complex. The measurement took place in a flow-through system. Interferences from phosphate, metal ions and others were eliminated. The results of a turbidimetric measurement, a spectrophotometric measurement with thorin, an automatic titration and the proposed method are compared. The latter allows the determination of sulphate in the range of 1.4–60 mol·l–1. The standard deviation is 0.3–0.6 mol·l–1, depending on the type of sample (water) analysed. A determination takes 1.5min.
Photometric in einem DurchflußsystemBestimmung von Sulphat mit Dimethylsulfonazo(III) in Umweltmaterial mit Hilfe eines Durchflußsystems
Zusammenfassung Sulfat wurde in verschiedenen Umweltproben durch Messung der Extinktion nach Reaktion mit dem Barium(II)-dimethylsulfonazo(III)-komplex im Durchflußsystem bestimmt. Störungen von Phosphat, Metallionen, u.a. wurden beseitigt. Die Ergebnisse einer turbidimetrischen, einer photometrischen, einer automatischen Titration und der vorgeschlagenen Methode werden verglichen. Die Methode ermöglicht die Sulfatbestimmung im Bereich von 1,4–60 mol·l–1. Die Standardabweichung beträgt 0,3–0,6 mol· l–1 je nach Typ des Probematerials (Wasser). Eine Bestimmung erfordert 1,5min.
  相似文献   

15.
A capillary zone electrophoresis method using indirect UV detection for the analysis of chloride and sulfate in alcohol fuel samples was developed. The anions were analyzed in less than 3 min using an electrolyte containing 10 mmol l–1 chromate and 0.75 mmol l–1 hexamethonium bromide (HMB) as electroosmotic flow modifier. Coefficients of variation were better than 0.6% for migration time (n=10) and between 2.05 and 2.82% for peak area repeatabilities. Analytical curves of peak area versus concentration in the range of 0.065–0.65 mg kg–1 for chloride and 0.25–4.0 mg kg–1 for sulfate were linear with coefficients of correlation higher than 0.9996. The limits of detection for sulfate and chloride were 0.033 and 0.041 mg kg–1, respectively. Recovery values ranged from 85 to 103%. The method was successfully applied for the quantification of sulfate and chloride in five alcohol fuel samples. The concentration of sulfate varied from 0.45 to 3.12 mg kg–1. Chloride concentrations were below the methods LOD.  相似文献   

16.
Diet samples were collected by a duplicate portion study of Japanese adults in two districts, a newly-rising town and an established seaside village, of Ishikawa Prefecture, which faces the Sea of Japan. Uranium concentrations in a total of 80 diet samples were determined by -spectrometry after chemical separation. No marked differences between the two districts were found regarding characteristics of food consumption in thirteen categories and in daily intake of238U per person. The daily intake of238U per person ranged from 1.1 to 40 mBq with a geometric mean value of 9.6±2.1 mBq. The234U/238U activity ratios ranged from 0.7–1.5, with most being from 1.0–1.2. The internal dose estimation system (IDES) was completed with Japanese physical parameters and other parameters of ICRP Publication 30, and then the annaul effective dose equivalent was estimated as 3·10–7 Sv for238U in a Japanese adult.  相似文献   

17.
Possibilities of the method based on both the selective separation of radioiodine from milk using anion-exchange resin as well as the131I counting in heterogeneous mixture of this anex with a liquid scintillator are presented. For samples of 4 dm3 volumes, the separation and counting efficiencies about 78% and 45% are achieved. Under the same experimental conditions the background rate is about 0.25 CPS /15 CPM/ and the LLD corresponds to about 7 mBq.dm–3 /0.2 pCi. dm–3/.  相似文献   

18.
A new RNAA procedure was developed capable of low level determination of thallium in biological and environmental samples. After high fluence neutron irradiation in a nuclear reactor, wet ashing of samples and T1(I) separation by solvent extraction with sodium diethyldithiocarbamate at pH 13, several types of counting were employed to compare their detection limits and to utilize the self-validation principle of NAA. The following measurement modes were used: High efficiency counting of -rays of202T1 and Hg X-rays produced on decay of204T1 using a well-type HPGe detector, combined ray and -counting of204T1 with the aid of a HPGe planar detector, and liquid scintillation counting and counting of Cerenkov radiation of -particles of204T1. The lowest detection limit of 0.034 ng of T1 was achieved on liquid scintillation counting of204T1. The method was applied for the analysis of biological NIST SRMs 1515, 1573a, 1577b and environmental NIST SRM 1633a. Good agreement was found between the thallium certified value in SRM 1633a and values determined in this work by all counting modes. For SRM 1573a, results in agreement were obtained by two counting modes, while counting of Hg X-rays of204T1 was only used for SRMs 1515 and 1577b.  相似文献   

19.
Continuous measurements of atmospheric222Rn were made for the past three years by the Environmental Measurements Laboratory (EML) at the Atmosphere/Ocean Chemistry Experiment site located at Tudor Hill, Bermuda and at the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Mauna Loa Observatory. The222Rn analyzer is based on the two-filter tube method. At the Bermuda site, monthly median222Rn concentration range from 50 to 700 mBq m–3, and the concentrations vary seasonally, with a maximum in the winter and a minimum in the summer. The concentrations are significantly elevated when local winds traverse the island. At MLO, monthly median222Rn concentrations range from 100 mBq m–3 during the fall months to 400 mBq m–3 during the spring months. The springtime maximum values correspond to periods of rapid transport in the free troposphere from the Asian continent, corroborated by backward air mass trajectories. The222Rn data are also used to help decipher local daily upslope/downslope conditions present at MLO. This study illustrates the value of atmospheric222Rn monitoring, when screened through the filter of local meteorology, in studying the transport of continental air to the oceans, as well as the dynamics of local meteorological effects.  相似文献   

20.
Two methods are presented for a fast, accurate and precise determination of210Pb in industrial samples with a calcium-phosphate and-sulphate matrix. One method combinessolid-liquid extraction on a Pb-selective column Sr*Spec (Eichrom) with gamma-ray spectrometry of210Pb and can be applied to samples >10 g for aselective 210Pb determination. The yield is determined gravimetrically. The detection limit is 380 mBq for a 24 h counting period. The other method combineschromatography on Sr*Spec with liquid scintillation counting of210Pb for asensitive 210Pb determination and can be applied to samples of up to 1 g. The yield is determined on-line by the UV signal of PbEDTA. The detection limit is 70 mBq for a 2 h counting period. Aspects of accuracy, precision, selectivity, sensitivity and the application of both methods to phosphogypsum and phosphate ores are presented.  相似文献   

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