氢化物-原子荧光光谱法测定大气沉降物中砷含量

大气沉降物中砷的测定传统方法干扰多,本文针对大气沉降物样品的复杂性,在样品中加入盐酸、硝酸、高氯酸于电热板上加热消解,能有效的消除大量有机质对测量结果的干扰,为大气沉降物研究工作提供更为精准的检测数据。该方法能有效的消除基体干扰,分析成本低,测定的精密度高、准确性好,相对标准偏差(RSD)低于2.0%,样品加标回收率高于90%。     

Chemical fraction of radiactive cesium in atmospheric aerosol in Prague after the Chernobyl accident

Aerosol filters exposed during the period of direct contamination after the NPP accident at Chernobyl have been analyzed with the aim to determine the physicochemical forms of¹³⁷Cs. A modified sequential analysis of solubility according to Tessier was used. It was shown that the content of water-soluble radiocesium fraction (about 45%) was substantially lower when compared with the analysis results of aerosols collected in the U.K. Another marked difference was found in the case of undissolved residue, where, on the contrary, the¹³⁷Cs content was higher. No significant differences were found in the composition of samples collected during the time period of, May 1–May 6, 1986. In a sample collected in a later period a lower percentage of water soluble¹³⁷Cs fraction and a higher percentage of¹³⁷Cs in the undissolved residue was found.     

Chernobyl-derived radiocesium in some pharmaceutical plants

The cesium rarioactivity (owing to¹³⁴Cs and¹³⁷Cs) in a number of wild plants of phamaceutical interest harvested in Transylvania was followed during the 1986–1994 period. The data give information on major pathways of vegetable organism contamination through lives from fallout and resuspention and by root uptake from contaminated soil.     

Measurement of radiocesium in Irish peatland soils

Results are presented for soils taken from twelve peatland sites in Ireland. Two depth horizons, 0–5 and 5–15 cm, were sampled on each site and sampling was carried out in summer and autumn. Deposition of Chernobyl¹³⁷Cs varied between 0.4 and 4.6 kBq m^–2, which is at the lower end of values reported by other authors for Irish agricultural soils. The data showed that the relative percentages of activity and deposition remained internally consistent in each soil horizon for Chernobyl and weapons fallout sources on both sampling occasions: this provided evidence that sampling and analytical procedures were consistent. An apparent reversal in the relative importance of weapons fallout in soils was found when deposition data were compared to the same data presented in activity format, and this same reversal was found for both soil horizons. Different conclusions may erroneously be drawn from data depending on the parameter by which we make measurements. Presentation of results should be carefully considered and depends on the purpose for which a study is intended. A statistically significant change in bulk density of the deeper soil horizon was found between summer and autumn. Changes in bulk density important to bear in mind that in addition to analytical errors, sampling methods can only provide estimations which themselves have inherent sources of error.     

Migration of radiocesium in a zeolite-solution system

Some properties of natural zeolite from Zaloka gorica, Slovenia, Yugoslavia were investigated to establish its applicability in solidification and for storage purposes of radioactive waste. It was found that this material is a rather good sorber for cesium, with a capacity of about 0.6 meq g^–1. The migration rate of Cs⁺ in a system ion exchanger-aqueous solution was investigated and correlated with the sorption behaviour of cesium in a system. The leaching rate of cesium from concrete containing zeolite was measured.     

Experimental and modeling studies of radiocesium retention in soils

A two-compartment model was used to describe the irreversible sorption behavior of ¹³⁷Cs on frayed edge sites (FES) of finite capacity in soils in Hong Kong reservoir. The sorption rate was assumed to depend on factors like the fractional water activity concentration, the difference between the activity concentration of ¹³⁷Cs in aqueous phase and that in particulate phase, and the number of available sorption sites. By varying the exponents of the different factors, very good fitting was obtained between experimental data and theory. A relationship between the number of available frayed edge sites and the mass of soil was proposed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Behavior of three atmospheric tracers in a pilot-scale coal combustor

Solutions of three useful atmospheric particle tracer materials, i.e., isotopically-enriched ¹⁹⁶Hg, and organometallic complexes of ¹⁴⁷Nd (T _1/2 = 11 d) and Ir, were dispersed into a pilot-scale coal combuster to determine partitioning between flue gas and suspended particle phases for Nd and Ir, and information on the chemical form of Hg tracer using nuclear analytical methods. Flue gas samples for ¹⁴⁷Nd, and Ir analyses were collected using cascade impactors at reduced and near flue gas temperatures; ¹⁹⁶Hg was sampled using an impinger method, and analyzed for ¹⁹⁶Hg after activation on cystine paper and by atomic absorption for total Hg. Solvent extracts of the impactor samples were also analyzed to determine the integrity of the tracer complexes. The results indicate that interaction with the particles tends to degrade the complexes, that major fractions become associated with particles, and that 96% of the Hg tracer was collected as HgCl₂, whereas, 85% of the natural Hg was collected as Hg^o.     

Uptake of radiocesium and alkali metals by mushrooms

Various mushrooms and soils were analyzed for alkali metals and for radiocesium. The obtained concentration factors of the nonradioactive Cs for mushrooms are not significantly different from that for vascular plants, whereas in the case of radiocesium the values found were orders of magnitude higher. The different behaviour of natural and radioactive cesium may be due to their disequilibrium in the ecosystems. The irradiation of man due to ingestion of contaminated mushrooms cannot cause a significant health risk.     

Chernobyl-derived radiocesium in mosses in the Black Sea area

Radiocesium (¹³⁴Cs and¹³⁷Cs) activity levels in mosses from the Black Sea area, northern Turkey, are reported following the Chernobyl accident during the period of 1989–1991. The cesium radionuclides were detected and measured in all the samples but other longlived radionuclides such as¹⁴⁴Ce and¹⁰⁶Ru were measured in only one sample. The present data support the fact that radioactivity monitoring in mosses can be useful to determine the lasting effect of radioactive contamination.     

Curium isotopes in Chernobyl fallout

In nuclear reactors plutonium and transplutonium isotopes are produced by multiple neutron capture of uranium and plutonium and are important for the energy production and their composition reflects the core burnout. Under normal operation these elements are not released to the environment in significant amounts. There are accordingly very few areas or source terms where exotic transplutonium elements, such as curium isotopes, can be studied in the environment. The Chernobyl accident provided a complex spectrum of fission and activation products in fallout while the relative amounts, compared to the core inventory, of refractory elements such as transuranium and transplutonium elements were small. The major alpha-activity consisted of ²⁴²Cm (T _1/2 = 163 d) that would have decayed after a few years. In this study we have demonstrated the presence of so called supported ²⁴²Cm from the long-lived ²⁴²Am^m (T _1/2 = 141 a) in environmental samples, following fallout from the Chernobyl accident. It has also been possible to assess the core burn up by using the data obtained for the Cm isotopes. The curium isotopes ²⁴³Cm (T _1/2 = 29.1 a) and ²⁴⁴Cm (T _1/2 = 18.1 a) cannot be resolved by conventional alpha-spectrometry. The assessment of these isotopes in environmental samples contaminated from the Chernobyl accident has been made by studying the effective half-life of the mixture of the isotopes. The data are compared with those previously obtained by high-resolution alpha-spectrometry and spectral deconvolution.     

Geographical and vertical distribution of radiocesium levels in coniferous forest soils in Izmir

Preliminary picture of ¹³⁷Cs radioactivity levels in forested areas in and around Izmir is illustrated. Both activity concentrations and activity depositions of ¹³⁷Cs in soil samples were determined. Their values varied from 8.29±0.27 to 445±3.16 Bq.kg⁻¹ (d.w.) and 0.63±0.01 to 11.6±0.08 kBq.m^–2 (d.w.), respectively. It was found that while activity deposition of ¹³⁷Cs is normally distributed, activity concentration of ¹³⁷Cs is log-normally distributed in forest soils and the activity deposition is less variable than the activity concentration. Cesium-137 activities in soils increase with increasing elevation, annual average rainfall and soil organic matter.     

Fukushima-derived radiocesium in the western North Pacific in 2014

Journal of Radioanalytical and Nuclear Chemistry - In 2014, we measured activity concentration of radiocesium in the western North Pacific Ocean. In the north of Kuroshio Front high activity...     

Natural and fallout radioactivity measurement in Indian soils

The paper presents the results of high resolution gamma-spectrometric measurements of ¹³⁷Cs, ⁴⁰K, ²³²Th and ²³⁸U in Indian soils collected from 24 different places from normal natural radiation background areas. The depth profile of ¹³⁷Cs was studied at sampling sites. The paper also presents ¹³⁷Cs levels in top soil at Mumbai during 1986 to 2000. The results in Mumbai soil indicate clearly the accumulation from fallout only on the top soil and seasonal peaking during the beginning of the monsoon season.     

Spatial distribution of radioactive fallout in Poland

The spatial distribution of the post-Chernobyl radioactive fallout in Poland is presented. These results can be compared with results of computer simulations.     

Sorption of radiocesium on soils in the presence of electrolytes

The influence of background electrolytes (KCl, NH₄Cl, CTABr) in different concentrations on the sorption ability of radiocesium by measuring the distribution coefficient has been studied. Sorption isotherms of cesium for characterization of soil sorption ability were used. Sorption of cesium depends on its concentration and at least three different sorption sites are active in the sorption process. In the case of low cesium concentration, two very selective sites with high distribution coefficients are responsible for the sorption. With increasing cesium concentration in the aqueous phase, distribution coefficient is decreasing. Frayed edge sites of illite in soil and exchangeable potassium are probably responsible for nonlinear isotherms at low cesium concentrations. From sorption isotherms and determination of potassium by activation analysis, it was found that the capacity of very selective sites for different concentrations of background electrolyte was up to 7 mmol·kg^–1.     

Long-term monitoring of radiocesium deposition near the Fukushima Dai-ichi nuclear power plant: effect of interception of radiocesium on vegetables

In this study, gross alpha and beta radioactivity in food crops and surface soil collected from Ho Chi Minh City, Vietnam were measured. Based on the annual effective dose from ingestion of food crops, the degree of risk to human health was estimated. We found out that the obtained values of the dose do not exceed the WHO recommended level (290 µSv year^?1). The estimated soil-to-plant transfer factors for gross alpha (TF_α) and beta (TF_β) for food crops were also presented. It was found that TF_α varied in the range from 0.009 ± 0.005 to 0.99 ± 0.06, TF_β varied in the range from 2.26 ± 0.10 to 10.87 ± 0.53 and the maximum values of transfer factors were found in the root of ipomoea batatas.     

Isolation of radiocesium from a fission product mixture

A method of¹³⁷Cs isolation from strongly, acidic solutions of fission products is described, in which vanadyl ferrocyanide is used as a selective ion exchanger for cesium. The effects of the acidity of medium and the carrier concentration on the quantitative yield of separation have been studied and convenient conditions have been found for¹³⁷Cs isolation from the solution of fission products formed after irradiating uranium with neutrons.     

Factors affecting interaction of radiocesium with freshwater solids

The paper aims at the analysis of principal factors affecting the interaction of radiocesium with freshwater solids, important for the migration of radiocesium in rivers. Uptake of radiocesium by bottom sediments and suspended solids from small streams was studied as a function of pH and composition of aqueous phase, of the concentration of cesium in water and of the composition of freshwater solids, using laboratory model experiments. pH had negligible effect on the uptake in the pH range 5–9, the uptake decreased at pH values less than 3–5 depending on the nature and concentration of the solids. Addition of cations suppressed the uptake in the order K⁺>Na⁺>Ca²⁺, the suppression began at 0.001, 0.01 and 0.1 mol.dm^?3 concentration, respectively. Increase in cesium concentration in water caused a decrease of radiocesium uptake, but at very low concentrations of cesium combined with higher concentration of sediment (2g·dm^?3) the uptake was independent of cesium concentration. Removal of carbonates, oxidic coatings and organic matter from a sediment did not affect the sorption properties of the sediment. The nature of the effects found confirms that cesium is sorbed mainly by clay components of freshwater solids. Results obtained are compared with literature data and conclusions are drawn on the importance of the factors studied for modelling of radiocesium migration in rivers.