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1.
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   

2.
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   

3.
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   

4.
Quantitative environmental criteria for the radiation protection of aquatic ecosystems, namely, reference concentrations of radionuclides in water are developed. If activity concentrations of radionuclides do not exceed these levels, aquatic biota can be considered completely protected from the negative effects of ionizing radiation. Reference concentrations of radionuclides in environmental objects can be compared directly with the measurement data on radioactive contamination parameters that allows using them for the monitoring data interpretation. Reference concentrations of anthropogenic radionuclides in the sea and fresh water are calculated using the environmental criteria and are compared to the values of reference concentrations computed using the hygienic criterion. It is demonstrated that the current levels of concentration of 90Sr, 137Cs, and tritium in the seas, rivers, and lakes of Russia are considerably lower than the values of reference concentrations of these radionuclides calculated using the environmental criterion.  相似文献   

5.
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   

6.
A multi-chamber model of radioactivity migration in reservoirs was developed. It describes transport of radioactive substances in water and in bed sediments taking into account sorbtion of radionuclides on suspended particles. The model provides higher resolution than simplified chamber models do. At the same time, unlike complex two- or three-dimensional dynamic models, it does not require hard-to-obtain data such as detailed data on bathymetry, currents and winds. The model was included into the Sybilla program code that was developed in the framework of the Rosatom project called PRORYV. The model was verified against the observed data on the contamination of the Kiev Reservoir with 137Cs in 1986.  相似文献   

7.
The results of modeling of 89, 90Sr, 137Cs, and 239, 240Pu migration in the Techa River are compared with observed data. It is shown that taking into account of the process of mass exchange between the main stream of a river and underflow is important for adequate modeling of migration and accumulation of radiative substances in a river. It is difficult to obtain results of modeling corresponding to the observed data if the process is neglected. Taking into account the mass exchange is especially important in developing models for long enough rivers that were polluted by radionuclides during long time. Authors believe that, in future, the considered aspects of modeling radioactive substances in rivers can be generalized on chemical polluting substances with similar physical and chemical properties, for example, heavy metals, phenols, etc.  相似文献   

8.
Concentrations of natural 7Be in air and rainwater were monitored for one year at Hokitika, New Zealand. The mean airborne concentration was 3.1±1.3 mBq m–3, the mean Hokitika, New Zealand. The mean airborne concentration was 3.1±1.3 mBq m–3, the mean concentration in rainwater was 2600±1200 Bq m–3, and the mean total deposition was estimated to be 130±99 Bq m–2 wk–1. Most of the 7Be was wet deposited and the washout ratio was independent of precipitation amount. A significant linear relationship exists between the weekly wet deposition flux and weekly precipitation at this high-rainfall site.  相似文献   

9.
Changes in the frequency of precipitation as a result of a changing climate, as well as anthropogenic induced deposition of nitrogen (N), both have the potential to alter grassland productivity and diversity. Central U.S. weather patterns are dominated by three major air mass trajectories including regional sources from the Gulf of Mexico (marine tropical, Mt), the Pacific Northwest (mild pacific, mP), and the Desert Southwest (continental tropical, Ct). In this work, the Hybrid Single Particle Lagrangian Integrated Trajectory model was used to determine trends in the proportion of precipitation events from these air mass sources from 1983 to 2006 relative to Konza Prairie Biological Station (KPBS), KS. The annual volume-weighted mean (VWM) concentrations and wet deposition of a variety of precipitation dissolved solutes were linked to source regions north or south of KPBS. The proportion of precipitation events from Mt significantly increased, while the proportion of events from Ct and mP decreased significantly over the study period. The annual VWM concentrations of most solutes were typically higher from precipitation sourced to the north of KPBS. However, wet deposition of four ecologically relevant solutes (NH4+, NO3?, H+, and SO4?2) was higher from events from the southern region, likely due to higher precipitation amounts. The proportion of reduced N increased significantly over the study period but was not affected by source region despite the higher use of fertilizers for agriculture in the northern source region. Given the location of this site relative to three dominant air mass paths, future shifts in these patterns will likely impact wet nutrient deposition.  相似文献   

10.
The acidification of precipitation and the wet removal of pollutants in South China in spring are evaluated by using a one dimensional, time-dependent, physico-chemical model of stratiform clouds. The results are consistent with the mean field data. In the typical condition, the in-cloud scavenging of gases and aerosols is the major removal process at the begining of rainfall, then fractions of below-cloud scavenging of S(VI) from S(IV) oxidation, NH3, HNO3 and particles increase gradually. It can be treated as an irreversible process. Numerical tests show that the concentration of oxidants, H2O2 can affect wet removal of SO2, as well as the formation and deposition amount of S(VI). The convergence of airflow can compensate partially the depletion of pollutants by wet removal.  相似文献   

11.
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   

12.
Bryansk Polesie is the most 137Cs-contaminated region of the Russian Federation after the Chernobyl NPP accident, where in 2007 (i.e., 21 years after the accident), the radiation monitoring was conducted within the Russia-Belarus Union State Program. The paper is based on the comparison of data obtained in the settlements and at the nearby landscape sites outside the villages. The 137Cs content variability in the most spread in Polesie soils, the podzols, is considered using observations obtained at the monitoring sites in Svyatsk and Demenka. It is shown that 137Cs is fixed at the surface, in the upper soil horizons, which is explained by a high soil sorption capacity. Vast crest-sink floodplains with the great contrast range of the hydromorphic features, which cause great variability of the 137Cs vertical distribution, are typical for the Polesie landscape; this fact is confirmed by observations obtained at the monitoring sites located in Starye Bobovichi and Ushcherpie. It is shown that Polesie pine forest contamination maintains higher contamination density levels compared to the nearby settlements, pastures, and meadow lands in the fluvial plains. Extrapolation of the contamination density data obtained within the first decade after the accident as of 2007, performed with allowance for the correction for decay and the comparison of these estimates with the new data accumulated in the recent years, does not show any significant contradiction.  相似文献   

13.
一次重雾霾天气成因及湿清除特征分析   总被引：1，自引：1，他引：0  
为了深入了解发生在武汉地区一次重雾霾天气过程的气象条件、污染源和污染物的湿清除特征,本文利用空气质量监测资料、地面观测资料和遥感火点监测资料和实测雨滴谱资料,详细分析了这次过程。结果表明:此次持续10 d的重雾霾天气过程发生在高压天气系统和静风条件下,辐射降温形成的稳定逆温边界层结构有利于污染气溶胶的积累和雾霾的形成和发展,尤其是来自南方持续不断的湿平流使雾霾天气得以长时间持续和发展,整个雾霾天气期间能见度均小于2 km,最低能见度不足50 m。2014年11月23~24日降水过程对此类污染物有明显的清除效果,清除率最高的是颗粒物污染,NO_2、SO_2和CO次之,最差的是O_3,通过与Scott(1982)按平均碰并系数E(E=0.65)得到的清除率和雨强的关系比较,武汉地区稳定性降水对气溶胶的平均碰并系数可取0.25~0.35。  相似文献   

14.
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   

15.
Both aerosol and rainwater samples were collected and analyzed for ionic species at a coastal site in Southeast Asia over a period of 9 months (January–September 2006) covering different monsoons. In general, the occurrence and distribution of ionic species showed a distinct seasonal variation in response to changes in air mass origins. Real-time physical characterization of aerosol particles during rain events showed changes in particle number distributions which were used to assess particle removal processes associated with precipitation, or scavenging. The mean scavenging coefficients for particles in the range 10–500 nm and 500–10 μm were 7.0 × 10−5 ± 2.8 × 10−5 s−1 and 1.9 × 10−4 ± 1.6 × 10−5 s−1, respectively. A critical analysis of the scavenging coefficients obtained from this study suggested that the wet removal of aerosol particles was greatly influenced by rain intensity, and was particle size-dependent as well. The scavenging ratios, another parameter used to characterize particle removal processes by precipitation, for NH4 +, Cl−, SO4 2−, and NO3 − were found to be higher than those of Na+, K+, and Ca2+ of oceanic and crustal origins. This enrichment implied that gaseous species NH3, HCl, and HNO3 could also be washed out readily. These additional sources of ions in precipitation presumably counter-balanced the dilution effect caused by high total precipitation volume in the marine and tropical area.  相似文献   

16.
From the IGAC-DEBITS Africa network (IDAF), data sets on precipitation chemistry collected from the ‘wet savanna ecosystem’ site of Lamto (Côte d'Ivoire), are analyzed (1995–2002). Inorganic (Ca2 +, Mg2 +, Na+, K+, NH4 +, Cl?, SO4 2 ?, NO3 ?) and organic (HCOO?, CH3COO?) ions content were determined using Ion Chromatography. The analyzed 631 rainfall events represent 8420.9 mm of rainfall from a 9631.1 mm total. The precipitation chemistry at Lamto is influenced by four main sources: natural biogenic emissions from savanna soils (NO x and NH3), biomass burning (savanna and domestic fires), terrigeneous particles emissions from dry savanna soils, and marine compounds embedded in the summer monsoon. The inter-annual variability of the weighted volume mean concentration of chemical species linked with wet deposition fluctuates by ～ 20% over the period. Ammonium concentration is found to be the highest (17.6 μ eq.l? 1) from all IDAF sites belonging to the West Africa ecosystems. Ammonia sources are from domestic animals, fertilizers and biomass burning. In spite of the high potential acidity of 30.5 μ eq.l? 1 from NO3 ?, SO4 2 ?, HCOO? and CH3COO?, a relatively weak acidity is measured: 6.9 μ eq.l? 1. The 40% acid neutralization is explained by the acid gas – alkaline soil particles interaction. The remaining neutralization is from inclusion of gaseous ammonia. When results from Lamto, are compared with those from Banizoumbou (dry savanna) and Zoetele (equatorial forest), a regional view for wet tropospheric chemistry processes is obtained. The high concentration of the particulate phase in precipitation emphasizes the importance of multiphases processes between gases and particles in the atmospheric chemistry of the West Africa ecosystems. For example, the nss Ca2 + precipitation content, main indicator of terrigeneous particles, goes from 30.8 μ eq.l? 1 in dry savanna to 9.2 μ eq.l? 1 at Lamto and 8.9 μ eq.l? 1 in the Cameroon forest. A similar gradient is obtained for rainfall mineral particles precipitation content with contribution of 80% in dry savanna, 40% in wet savanna, and 20% in the equatorial forest.  相似文献   

17.
The Chernobyl NPP accident resulted, due to the western atmospheric transfer, in the formation of a pattern crossing the Central Russian Upland and its surroundings in the latitudinal direction. A volatile long–lived dose-forming radionuclide 137Cs prevailed in the fallout. A peculiar character of the Central Russian Upland division by valleys and balkas could result in a 20–year period in radioactivity displacement down the slop to valleys. This article is devoted to checking the significance of such changes. The issue on revealing the differences between the measured contamination density values 21 years after the depositions and the expected values (calculated with the correction for 137Cs decay) is also under consideration.  相似文献   

18.
Within the framework of IDAF (IGAC DEBITS AFRICA: International GlobalAtmospheric Chemistry/DEposition of Biogeochemically Important TraceSpecies/Africa) network, data analysis is realised on precipitation chemical composition collected in Zoétélé, in Southern Cameroon. This station, located atabout 200 km from the Atlantic Ocean, is representative of a so-called `Evergreen Equatorial Forest' ecosystem. An automatic wet-only precipitation collector was operated at the station from 1996 to 2000. The rainfall regime, associated with eastward advection of moist and cool monsoon air masses, amounts to an average of 1700 mm/year. Inorganic and organic content of the precipitation were determined by IC in 234 rainfall events, representing a total 4,583 mm of rainfall from an overall of 7,100 mm.The mean annual precipitation chemistry and wet deposition fluxes characteristic of an African equatorial forest are quantified. Typical atmospheric gases and particles sources influence the precipitation chemical content and the associated deposition of chemical species. Indeed, hydrogen concentration is the highest (12.0 eq.L–1) of the IDAF measurements, leading to acid rains with a low mean pH 4.92. The mineral species are dominated by nitrogenous compounds (NH4 +:10.5 and NO3 –: 6.9 eq.L–1), Ca2+ (8.9 eq.L–1) and SO4 2 – 5.1 eq.L–1. Relationship between Ca2 + and SO4 2 – indicated aterrigeneous particulate source and an additional SO4 2 – contributionprobably due to swamps and volcano emissions. Na+ and Cl–concentrations, around 4.0 eq.L–1, seem very low for this site,accounting for the marine source. Besides, strong correlations between NH4 +/K+/Cl– indicate the biomass burning originof these species. Accordingly, precipitation chemistry in Zoétéléis influenced by three major sources: biogenic emissions from soil and forest ecosystems, biomass burning from savannah, and terrigenous signature from particles emissions of arid zones; and three minor sources: marine, volcano and anthropogenic. In spite of the relatively low concentration of all these elements, the wet deposition is quite significant due to the high precipitation levels, with for example a nitrogenous compounds deposition of 34 mmol.m–2.yr–1.  相似文献   

19.
Formaldehyde levels were determined in various forms of atmospheric precipitation (rain, snow, road and roof runoff, throughfall) and deposition (rime, hoarfrost, dew) collected over twelve months at various locations in two large urban agglomerations and along two highways. HCHO was found in 303 of 500 samples analyzed, with concentrations ranging from 0.05 to 10.7 mg/dm3. The results confirmed the significant effect of vehicular traffic on formaldehyde levels in various forms of wet deposition. Correlations of formaldehyde levels with other parameters commonly monitored in precipitation and/or deposition were also examined. No correlation was found between HCHO levels and rain volume. On the other hand, positive correlations were found for hydrogen peroxide, non-sea-salt sulphate, nitrate, ammonia, and total organic carbon (TOC). In addition, the effect of selected meteorological parameters (temperature, wind speed, wind direction, rainfall) on the concentration of formaldehyde in various forms of precipitation and runoff (road runoff, roof runoff, throughfall) was studied. The only correlation found was that between HCHO concentration and daily rainfall.  相似文献   

20.
Wet-only, dry-only, bulk deposition and deposition of sedimentary particles and gases deposited after the last rain (DAR) were collected weekly at La Castanya station in the Montseny mountains (NE Spain, 41°46′N, 2°21′E) from February 2009 to July 2010. These samples were analysed for pH, alkalinity, and the concentrations of major ions (Cl?, NO3 ?, SO4 2?, Na+, K+, Ca2+, Mg2+, NH4 +). Significant differences were observed between bulk and wet-only precipitation, with an enrichment of ions associated to coarse particles in bulk deposition. The comparison between wet and dry fluxes revealed that the removal of compounds at Montseny occurred mainly by wet deposition, which accounted for 74 % of total deposition. The dry flux was characterised by the predominance of K+, Ca2+ and Mg2+, which are related to coarse particles. Bulk collection methods at Montseny were considered representative of total atmospheric deposition, since bulk deposition plus DAR accounted for 97 % of total deposition measured with wet and dry-only collection devices. Thus, bulk deposition collectors can be recommended for deposition networks at remote sites (lacking electricity connection) in environments, where coarse particles are a predominant fraction of the aerosol mass.  相似文献   

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