首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Experimental field and laboratory studies on washout of radionuclides from the snow cover during snow melting were carried out in the winter of 2005/06. In the field studies, a specially equipped runoff site was used. In the laboratory conditions, the experiments were conducted using prepared soil monoliths. In the winter of 2006, 25 g/m2 of water-free cesium chloride (CsCl) and 25 g/m3 of strontium chloride (SrCl2) were put onto the snow cover surface of the runoff site. The snow surface of the soil monolith was coated with a 137Cs-bearing solution, then with SrCl2. Under experimental conditions, practically no surface runoff from the runoff site was recorded. The experiments with the soil monoliths demonstrated that the coefficient of the liquid washout of 137Cs normalized to the runoff layer was within 0.9 × 10?6–1.2 × 10?4 mm?1, and that of 90Sr normalized to the runoff layer was within 2 × 10?–1.6 × 10?4 mm?1.  相似文献   

2.
Experimental investigations under field and laboratory conditions of 137Cs washout from the periodically frozen and thawed soils were carried out. The experiments demonstrated that the amount of cesium washed out from the soil after freezing was much larger than from the non-frozen soils and by its intensity it corresponds to the washout under the influence of intensifiers. This fact allows recommending cheap and technologically simple measures for the in-snow runoff control to rehabilitate the contaminated lands.  相似文献   

3.
The estimate of the release of radioactive substances (133Xe, 131I, and 137Cs) into the atmosphere from the Fukushima Daiichi nuclear disaster is presented. It was obtained using the FLEXPART Lagrangian dispersion model and the data of local ground-based measurements of radiation dose rate. The computation period covers the active phase of the nuclear disaster that lasted 20 days after the tsunami. To get the quantitative characteristics of emissions of radioactive substances, the inverse modeling based on the Bayesian approach is used. The emissions were estimated for three altitudes. The total emissions are equal to 2.1 + 0.4 kg (14 000 + 2700 PBq) for 133Xe, (3.8 + 0.4) x 10-2 kg (174 + + 18 PBq) for 131I, and 5.7 + 1.2 kg (18 + 4 PBq) for 137Cs that is consistent with the results of other studies. Retrieved emissions were used to provide the forward modeling for mapping the areas of radionuclide deposition. The developed method of retrieving the emission of radioactive substances makes a useful instrument that operationally estimates and localizes the areas of potential pollution in case of nuclear accidents and could be used for making decisions on the population evacuation.  相似文献   

4.
The issues of assessing variability of 137Cs fallout of global and Chernobyl origin at reference sites are discussed with a purpose to use this isotope as a tracer for estimating the rates of erosion-accumulative processes. It is shown that local variability of soil contamination by 137Cs at reference sites is within 7–20%, which makes it possible to use the isotope as a tracer. When studies are conducted within drainage basins, the available trend of the atmospheric 137Cs fallout should be taken into account in assessing the soil and sedimentation redistribution.  相似文献   

5.
The series of δ18O values is presented for all precipitation events in Moscow in 2014. Precipitation samples were taken at the observation site of the Meteorological Observatory of Lomonosov Moscow State University (MSU MO), and the isotopic analysis was carried out in the isotopic laboratory of the Department of Geography of MSU. The concentration of stable 18O in precipitation over Moscow in 2014 varied from -0.09 to -26.29‰. The maximum amplitudes of δ18O were registered in March-April and October. The pronounced interrelation was revealed between the oxygen isotopic composition of precipitation and surface air temperature (the correlation coefficient is 0.85). The computation of back trajectories of air masses and the analysis of weather charts demonstrated that the most isotopically light precipitation is typical of relatively cold air masses slowly moving over the continent during the last five days before precipitation. In this case, the ongoing condensation leads to the progressive isotopic depletion of precipitation (more and more isotope-depleted precipitation is registered). On the contrary, fast air transport from the middle and even from high latitudes of the Atlantic Ocean leads to the relatively constant of δ18O values of precipitation.  相似文献   

6.
The carbon kinetic isotope effects (KIEs) in the reactions of several unsaturated hydrocarbons with chlorine atoms were measured at room temperature and ambient pressure using gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS). All measured KIEs, defined as the ratio of the rate constants for the unlabeled and labeled hydrocarbon reaction k 12/k 13, are greater than unity or normal KIEs. The KIEs, reported in per mil according to Cl ɛ = (k 12/k 13−1) × 1000‰ with the number of experimental determinations in parenthesis, are as follows: ethene, 5.65 ± 0.34 (1); propene, 5.56 ± 0.18 (2); 1-butene, 5.93 ± 1.16 (1); 1-pentene, 4.86 ± 0.63 (1); cyclopentene, 3.75 ± 0.14 (1); toluene, 2.89 ± 0.31 (2); ethylbenzene, 2.17 ± 0.17 (2); o-xylene, 1.85 ± 0.54 (2). To our knowledge, these are the first reported KIE measurements for reactions of unsaturated NMHC with Cl atoms. Relative rate constants were determined concurrently to the KIE measurements. For the reactions of cyclopentene and ethylbenzene with Cl atoms, no rate constant has been reported in refereed literature. Our measured rate constants are: cyclopentene (7.32 ± 0.88) relative to propene (2.68 ± 0.32); ethylbenzene (1.15 ± 0.04) relative to o-xylene (1.35 ± 0.21), all × 10−10 cm3 molecule−1 s−1. The KIEs in reactions of aromatic hydrocarbons with Cl atoms are similar to previously reported KIEs in Cl-reactions of alkanes with the same numbers of carbon atoms. Unlike the KIEs for previously studied gas-phase hydrocarbon reactions, the KIEs for alkene–Cl reactions do not exhibit a simple inverse dependence on carbon number. This can be explained by competing contributions of normal and inverse isotope effects of individual steps in the reaction mechanism. Implications for the symmetries of the transition state structures in these reactions and the potential relevance of Cl-atom reactions on stable carbon isotope ratios of atmospheric NMHC are discussed.  相似文献   

7.
The analysis of possible mechanisms of 137Cs concentration changes in surface waters was performed in the process of preparation of reliable long-range forecasts of radioactive river contamination after the Chernobyl accident. The following mechanisms were considered: (1) radioactive decay; (2) advective transport with river waters; (3) irreversible sorption; (4) vertical migration deep into bottom sediments due to diffusion; (5) burial in clean bottom sediments. The data published on 137Cs monitoring at Dobrush, on the Iput’ River in Belarus were used in the analysis. It is shown that the best agreement with the experimental results is achieved when the second, third, and fifth mechanisms are used in calculations. However, a dominating mechanism still cannot be chosen at the present stage of our study. Most probably, all of these mechanisms act simultaneously.  相似文献   

8.
  相似文献   

9.
A method for identifying past radiation events from dated layers of bottom sediments in stagnant water bodies is described. Results of an experimental study (2005–2006) of the samples of bottom sediments in the pond of the Timiryazev dendropark in Moscow are considered. The sediment layers are dated with 210Pb. The same radionuclide is used as a tracer for calculating the rate of sedimentation in the pond, which is estimated at 0.3–0.4 cm/year. The maximum 137Cs values are detected in the 0–24 cm column at depths of 7 and 13 cm. The 137Cs peak at a depth of 13 cm is dated as 1963, which reflects the maximum global fallout from the atmospheric nuclear weapon tests. A small peak of this radionuclide at 7 cm is dated as 1986. It appears to be attributed to the long-range fallout after the Chernobyl NPP accident. The origin of the 137Cs maximum at a depth of 13–14 cm is confirmed by characteristic ratios of radionuclide pairs available in the global fallout in the Moscow region. The ratios of 90Sr/137Cs = 0.6 and 239,240Pu/137Cs = 0.03 in the 13–14 cm layer are characteristic of the global radioactive fallout from nuclear explosions. In the layers above this maximum, such ratios vary sharply toward the enhanced 137Cs content in the fallout.  相似文献   

10.
The thermohaline structure of waters in the East Siberian Sea coastal zone in September 2000, 2003, and 2004 is investigated. It is found that the spatial variability of thermohaline characteristics was determined by various synoptic conditions observed over the East Siberian Sea during the summer-autumn season and by fluctuations in the river discharge. In surface layers, plume fronts are identified. Under conditions of cyclonic atmospheric circulation of 2003, fresh waters spread as a narrow jet along the coast. During anticyclonic circulation of 2004, some meridional fronts existed. Horizontal gradients of thermohaline characteristics were 0.01–0.02°C/km and 0.03–0.07 psu/km off the Indigirka River and 0.02–0.03°C/km and 0.06–0.09 psu/km near the Kolyma River mouth being an order of magnitude less than the vertical ones. The stratification of coastal waters was amplified as the river and ice-melted runoff increased. In the thermohalocline, the average Brunt-Väisälä frequency was 0.042 s?1 (in 2000), 0.068 s?1 (in 2003), and 0.074 s?1 (in 2004).  相似文献   

11.
Major ion concentrations and strontium isotopic ratios (87Sr/86Sr) were measured in rainwater samples collected at the urban site of Lanzhou, a city located on the Loess Plateau in the arid and semi-arid areas of northwest China. The rainwater samples possessed alkaline pH, at a reference level of 5.6, with a range of 6.82 to 8.28 and a volume-weighted mean (VWM) pH value of 7.70. The alkaline character of rainwater in Lanzhou is due to the result of neutralization caused by the alkaline soil dusts which contain large amount of CaCO3. It was observed that Ca2+ was the most abundant cation with a VWM value of 886 µeq l− 1 (115–2184 µeq l− 1), accounting for 87.8% of the total cations. Without considering HCO3−, SO42− and NO3− were dominant among the anions, accounting for 64.2% and 23.0%, respectively, of the total measured anions. Using Na as an indicator of marine origin and Al for terrestrial inputs, the proportions of sea salt and non-sea-salt elements were estimated from elemental ratios. The precipitation in this region has typical continental characteristics. The Sr concentrations varied from 0.004 to 0.885 µmol l− 1, and strontium isotopic ratios (87Sr/86Sr) lay in the range of 0.71025–0.71302, with an average of 0.71143. The 87Sr/86Sr ratios of Lanzhou rainwater are higher than that of seawater, which reflects contributions from the radiogenic Sr sources of the aerosols. The most suitable candidate for the source would be the soil dust originating from local and distant loess and desert areas. The 87Sr/86Sr ratios were used to characterize different sources of base cations in rainwater, suggesting that the samples could be interpreted in terms of combinations of at least three components: soil dust derived from the Loess Plateau and desert areas in northwest China (with 87Sr/86Sr ~ 0.7130), seawater (with 87Sr/86Sr ~ 0.70917), and anthropogenic inputs (with 87Sr/86Sr ~ 0.7103). The high 87Sr/86Sr ratio and Ca and Sr content in the rainwater from Lanzhou can be attributed to the dissolution of calcium carbonate in soil dust.  相似文献   

12.
Chernobyl radioactivity in precipitation was measured at Tsukuba, Japan, as were both surface-air concentrations and particle-size distributions of Chernobyl-released radionuclides. To understand the wet removal processes of the Chernobyl radionuclides, i.e.137Cs,103Ru, and90Sr, wet deposition velocities were calculated. The wet deposition velocities of the Chernobyl radioactivity for individual rainfall events varied largely. The wet deposition velocity is given as the product of washout ratio and rainfall rate. Typically, it was found that the washout ratios of90Sr are systematically larger than those of137Cs. In order to explain this fact, we examined the relationship between the washout ratios and particle sizes of radionuclide-bearing aerosols. A positive correlation between corrected washout ratios and particle size was found with a particle diameter range from 0.35 to 1.2 µm. The result strongly suggests that the factors controlling the wet removal of the Chernobyl radioactivity for individual rainfall events are surface air concentration, particle size, and rainfall rate, rather than precipitation amount, which is in agreement with previous understandings. This suggests that high contamination areas of radioactivity are formed during heavy rainfall events with high rainfall rates in the case of tropospheric injection such as the Chernobyl accident.  相似文献   

13.
The estimates of 137Cs emissions from the accident happened in Elektrostal at the beginning of April 12, 2013 are presented. The transport of radionuclides and their dry and wet deposition on the surface are computed using the Lagrangian stochastic model of the NOSTRADAMUS software package worked out by Nuclear Safety Institute of Russian Academy of Sciences. Prognostic fields of wind (horizontal and vertical components) in the lower troposphere, precipitation, and vertical and horizontal turbulence diffusivity coefficients in the lower atmosphere (up to 4 km) were used as input data. Prognostic fields were obtained using the WRF-ARW numerical mesoscale model.  相似文献   

14.
Ocean emissions of inorganic and organic iodine compounds drive the biogeochemical cycle of iodine and produce reactive ozone-destroying iodine radicals that influence the oxidizing capacity of the atmosphere. Di-iodomethane (CH2I2) and chloro-iodomethane (CH2ICl) are the two most important organic iodine precursors in the marine boundary layer. Ship-borne measurements made during the TORERO (Tropical Ocean tRoposphere Exchange of Reactive halogens and Oxygenated VOC) field campaign in the east tropical Pacific Ocean in January/February 2012 revealed strong diurnal cycles of CH2I2 and CH2ICl in air and of CH2I2 in seawater. Both compounds are known to undergo rapid photolysis during the day, but models assume no night-time atmospheric losses. Surprisingly, the diurnal cycle of CH2I2 was lower in amplitude than that of CH2ICl, despite its faster photolysis rate. We speculate that night-time loss of CH2I2 occurs due to reaction with NO3 radicals. Indirect results from a laboratory study under ambient atmospheric boundary layer conditions indicate a k CH2I2+NO3 of ≤4 × 10?13 cm3 molecule?1 s?1; a previous kinetic study carried out at ≤100 Torr found k CH2I2+NO3 of 4 × 10?13 cm3 molecule?1 s?1. Using the 1-dimensional atmospheric THAMO model driven by sea-air fluxes calculated from the seawater and air measurements (averaging 1.8 +/? 0.8 nmol m?2 d?1 for CH2I2 and 3.7 +/? 0.8 nmol m?2 d?1 for CH2ICl), we show that the model overestimates night-time CH2I2 by >60 % but reaches good agreement with the measurements when the CH2I2 + NO3 reaction is included at 2–4 × 10?13 cm3 molecule?1 s?1. We conclude that the reaction has a significant effect on CH2I2 and helps reconcile observed and modeled concentrations. We recommend further direct measurements of this reaction under atmospheric conditions, including of product branching ratios.  相似文献   

15.
Using a single drop experiment, the uptake of NO3 radicals on aqueous solutions of the dye Alizarin Red S and NaCl was measured at 293 K. Uptake coefficients in the range (1.7–3.1) ⋅ 10− 3 were measured on Alizarin Red S solutions. The uptake coefficients measured on NaCl solutions were in the range of (1.1–2.0) ⋅ 10−3 depending on the salt concentration. Both experiments lead to a consistent result for the mass accommodation coefficient of αNO3 = (4.2− 1.7+2.2)⋅ 10−3. The product H(Dl kCl−II)0.5 for the NO3 radical was determined to be (1.9 ± 0.2) M atm− 1 cm s−0.5 M−0.5 s−0.5 by fitting the uptake data for the NaCl solutions to the so-called resistance model. The yield of the chemical NO3 radical source was characterized using UV-VIS and FT-IR spectroscopy. The amount of gas-phase NO3 radicals measured at elevated humidities was less than expected. Instead, a rise of the gas-phase HNO3 concentration was found indicating a conversion of gas-phase NO3 radicals to gas-phase HNO3 on the moist reactor walls.  相似文献   

16.
Abstract

An intercomparison of the Väisälä MicroCora system used in the Automated Shipboard Aerological Program (ASAP) and the Atmospheric Environment Service upper‐air system (GMD/ADRES) was conducted in May‐June 1983. Thirty‐three paired ascents were made. The ASAP system dry‐bulb temperatures averaged 0.3°C warmer. For the lowest 100 mb, the dew‐point temperature difference (ASAP ‐ GMD/ADRES) was near ‐1°C whereas for the 780–500 mb layer, the difference was 1°C. The wind component mean differences averaged were small but with a 4 m s?1 standard deviation.  相似文献   

17.
  相似文献   

18.
In the present study, the precipitation near Büyükçekmece Lake, which is one of the important drinking water sources of Istanbul city, was studied during October 2001–July 2002. Seventy-nine bulk precipitation samples were collected at two sampling stations near the Lake (41°2′35″N, 28°35′25″E and 41°5′30″N, 28°37′7″E). The study comprised the determination of H+, Cl−, NO3−, SO42−, NH4+, Na, K, Mg, Ca, Al, Ba, Fe, Cu and Mn concentrations in bulk deposition rain event samples. The average volume-weighted pH value was found to be 4.81, which points out that the rain is slightly acidic. High sulfate concentrations were observed together with high H+ ion values. Sulfur emissions were the major cause for the observed high hydrogen ion levels. On the basis of factor analysis and correlation matrix analysis, it has been found that in this region, acid neutralization is brought about by calcium rather than the ammonium ion. The varimax rotated factor analysis grouped the variables into four factors, which are crustal, marine and two anthropogenic sources.  相似文献   

19.
Carbon dioxide (CO2) is an important greenhouse gas that influences regional climate through disturbing the earth’s energy balance. The CO2 concentrations are usually prescribed homogenously in most climate models and the spatiotemporal variations of CO2 are neglected. To address this issue, a regional climate model (RegCM4) is modified to investigate the non-homogeneous distribution of CO2 and its effects on regional longwave radiation flux and temperature in East Asia. One-year simulation is performed with prescribed surface CO2 fluxes that include fossil fuel emission, biomass burning, air–sea exchange, and terrestrial biosphere flux. Two numerical experiments (one using constant prescribed CO2 concentrations in the radiation scheme and the other using the simulated CO2 concentrations that are spatially non-homogeneous) are conducted to assess the impact of non-homogeneous CO2 on the regional longwave radiation flux and temperature. Comparison of CO2 concentrations from the model with the observations from the GLOBALVIEW-CO2 network suggests that the model can well capture the spatiotemporal patterns of CO2 concentrations. Generally, high CO2 mixing ratios appear in the heavily industrialized eastern China in cold seasons, which probably relates to intensive human activities. The accommodation of non-homogeneous CO2 concentrations in the radiative transfer scheme leads to an annual mean change of–0.12 W m–2 in total sky surface upward longwave flux in East Asia. The experiment with non-homogeneous CO2 tends to yield a warmer lower troposphere. Surface temperature exhibits a maximum difference in summertime, ranging from–4.18 K to 3.88 K, when compared to its homogeneous counterpart. Our results indicate that the spatial and temporal distributions of CO2 have a considerable impact on regional longwave radiation flux and temperature, and should be taken into account in future climate modeling.  相似文献   

20.
The concentrations of PM10, PM2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India. The annual mean PM10 and PM2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) μgm−3 respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio of PM2.5/PM10 varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in summer and fine size particles in winter. The difference between the concentrations of PM10 and PM2.5, is deemed as the contribution of the coarse fraction (PM10−2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 μgm−3, 13.07%), mineral matter (12.32 μgm−3, 10.06%) and salt particles (4.92 μgm−3, 4.02%). PM2.5 are mainly made up of undetermined fractions (39.46 μgm−3, 40.9%), secondary inorganic aerosols (26.15 μgm−3, 27.1%), salt aerosols (22.48 μgm−3, 23.3%) and mineral matter (8.41 μgm−3, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered an annual mean of ∼14 (±12) μgm−3, which is significantly large compared to those observed at other locations in India. The source identifications are made for the ionic species in PM10 and PM2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl−, SO42−, K+, Na+, Ca2+, NO3− and Mg2+ with PM2.5 on one hand and Mg2+ with PM10 on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号