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941.
L. León Vintró P.I. Mitchell A. Omarova M. Burkitbayev H. Jiménez Nápoles N.D. Priest 《Journal of environmental radioactivity》2009
New data are reported on the concentrations, isotopic composition and speciation of americium, plutonium and uranium in surface and ground waters in the Sarzhal region of the Semipalatinsk Test Site, and an adjacent area including the settlement of Sarzhal. The data relate to filtered water and suspended particulate from (a) streams originating in the Degelen Mountains, (b) the Tel′kem 1 and Tel′kem 2 atomic craters, and (c) wells on farms located within the study area and at Sarzhal. The measurements show that 241Am, 239,240Pu and 238U concentrations in well waters within the study area are in the range 0.04–87 mBq dm−3, 0.7–99 mBq dm−3, and 74–213 mBq dm−3, respectively, and for 241Am and 239,240Pu are elevated above the levels expected solely on the basis of global fallout. Concentrations in streams sourced in the Degelen Mountains are similar, while concentrations in the two water-filled atomic craters are somewhat higher. Suspended particulate concentrations in well waters vary considerably, though median values are very low, at 0.01 mBq dm−3, 0.08 mBq dm−3 and 0.32 mBq dm−3 for 241Am, 239,240Pu and 238U, respectively. The 235U/238U isotopic ratio in almost all well and stream waters is slightly elevated above the ‘best estimate’ value for natural uranium worldwide, suggesting that some of the uranium in these waters is of test-site provenance. Redox analysis shows that on average most of the plutonium present in the microfiltered fraction of these waters is in a chemically reduced form (mean 69%; 95% confidence interval 53–85%). In the case of the atomic craters, the proportion is even higher. As expected, all of the americium present appears to be in a reduced form. Calculations suggest that annual committed effective doses to individual adults arising from the daily ingestion of these well waters are in the range 11–42 μSv (mean 21 μSv). Presently, the ground water feeding these wells would not appear to be contaminated with radioactivity from past underground testing in the Degelen Mountains or from the Tel′kem explosions. 相似文献
942.
A. Tieber H. Lettner P. Bossew A. Hubmer B. Sattler W. Hofmann 《Journal of environmental radioactivity》2009
Cryoconites are airborne sediments which accumulate on the surface of glaciers. In samples of cryoconites a temperate Austrian glacier high activity concentrations of anthropogenic radionuclides were found, which stem from global and Chernobyl fallouts. Radionuclides identified were 137Cs, 134Cs, 238Pu, 239+240Pu, 90Sr, 241Am, 60Co, 154Eu, 207Bi, and 125Sb. 相似文献
943.
The results of studies on postfire succession in larch forests of the permafrost zone are discussed. The main directions of successional processes in burned-out areas of different ages are described. It has been shown that secondary pyrogenic successions in larch forests follow the scheme of rapid regeneration without tree species replacement and the model of succession tolerance. Groups of plant species with different life strategies and indicator species characterizing different stages of the overgrowing of burned-out areas have been identified. 相似文献
944.
A. P. Gusev 《Russian Journal of Ecology》2009,40(3):160-165
Specific features of progressive succession in the vegetation of anthropogenically transformed landscapes in southeastern Belarus have been studied in permanent test plots. Using phytoindication scales proposed by Ellenberg (1974) and Tsyganov (1983), trends of changes in ecological conditions in the first years of succession have been revealed. 相似文献
945.
The paper is devoted to the phenomenon of methanogenic activity of woody debris, i.e., methane production in the course of wood decomposition by fungi, which are not directly involved in methane synthesis but form an initial link in the trophic chain leading to methanogenic archaea. Expert evaluation of probable amounts of methane emission is made. The results show that woody debris is an important global source of this greenhouse gas. 相似文献
946.
Specific ecogenetic features of solods in the forest-steppe zone has been studied, and the role of biotic and abiotic factors of soil formation has been estimated. Differentiation of soil horizons with respect to the physical clay fraction accounts for specific features of their moistening, which is reflected in the ratio of strongly and weakly crystallized forms of iron. Periodic changes in redox conditions results in iron segregation, and a high content of fulvic acids accounts for its eluvial migration. These processes are controlled by soil geochemical barriers. 相似文献
947.
The study focuses on evaluating factors that farmers consider relevant in adopting cassava production in five semi-arid zone
of West African countries. The study is based on primary data randomly collected as part of collaborative study of cassava
in semiarid zones of Africa (COSCASSA) village level survey from five West African countries namely: Nigeria, Ghana, Chad,
Niger and Burkina Faso. This study models effects of farm, farmer and technology specific factors on the decision of semi
arid farmers to adopt cassava into their farming system. By way of threshold decision models—Probit and Logit models, the
estimation of each country and the pooled data adoption models reveal different adoption models for the countries considered.
For each country, different variables appeared as major adoption shifters. Comparatively, the adoption models for Nigeria
and whole region appear to have the highest significance variables, being seven in number. This is followed by Chad (6), Ghana
(4), and Burkina Faso and Niger with three each. For the variables considered, distance to nearby urban market appears a major
adoption shifter in all the country, except for Niger. This is closely followed by contact with extension, variety, pest/disease
resistance and livestock feeds, which appear significant in four of the countries. Membership of cooperative societies appears
as the least adoption predictor, which is only significant in Chad republic. The study therefore recognizes the importance
of varietial characteristics and farmers’ characteristics in acceptance of cassava as a major root tuber crop in the semi
arid region of West Africa.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
948.
J. R. Park M. J. Stabler P. J. Jones S. R. Mortimer J. R. Tiffin R. B. Tranter 《Environment, Development and Sustainability》2009,11(4):735-750
The issue of the sustainable development of rural economies in England has recently received considerable attention. This
is because many of the poorest areas in the country are rural, often of high environmental quality, but suffering from high
unemployment and a lack of services and facilities. The rapid decline in agricultural incomes and in-migration of affluent
urban workers since 1990 has exacerbated economic inequality in such areas. A number of factors have the potential to drive
rural development and this paper applies, and considers, the feasibility of a method from the USA for combining economic and
environmental variables in a regional growth model to examine the hypothesis that environmental quality is an important determinant
of sustainable rural development in England. The model output suggests that, although environmental quality does play a role
in sustainable rural development in England there are other, more important, factors driving development. These include business
and communications infra-structure, the degree and opportunities for commuting and underlying employment prospects. The robustness
and limitations of the method for combining economic and environmental variables is discussed in relation to the spatial interrelatedness
of Local Authority Districts in England, and conclusions are drawn about areas for refinement and improvement of the method.
相似文献
J. R. ParkEmail: |
949.
Use and knowledge of fuelwood in three rural caatinga (dryland) communities in NE Brazil 总被引:1,自引:0,他引:1
I. M. M. Sá e Silva L. C. Marangon N. Hanazaki U. P. Albuquerque 《Environment, Development and Sustainability》2009,11(4):833-851
The woody species known, used, and preferred as fuelwood were examined in three rural communities within the county of Soledade,
Paraíba State, NE Brazil. Ethnobotanical information was collected using semi-structured interviews with more than 90% of
the local households (55 adult residents; 31 women, and 24 males). The interviewees cited 36 plant species as fuelwoods, distributed
among 30 genera and 15 families, in addition to two unidentified plants. The plant families represented by the largest numbers
of species were Euphorbiaceae, Anacardiaceae, Mimosaceae, Caesalpiniaceae, Sapotaceae, and Fabaceae. The species Caesalpinia pyramidalis Tul. (“catingueira”) was cited with the greatest frequency in all three communities. Within the communities we found significant
differences on the number of plants cited and actually used (p < 0.05), indicating that the residents knew more fuelwood species than they effectively harvest. The different distances
from the communities to the urban centers were not related to differences on the use or the size of the stocks of fuelwood.
Additionally, the study revealed that the communities examined still maintain a significant knowledge of the use of energy-providing
plants in spite of the widespread use of liquefied petroleum gas (LPG).
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
950.
The boundary between preferential flow and Richards-type flow is a priori set at a volumetric soil water content θ at which soil water diffusivity D (θ) = η (= 10− 6 m2 s− 1), where η is the kinematic viscosity. First we estimated with a hydrostatic approach from soil water retention curves the boundary, θK, between the structural pore domain, in which preferential flow occurs, and the matrix pore domain, in which Richards-type flow occurs. We then compared θK with θ that was derived from the respective soil hydrological property functions of same soil sample. Second, from in situ investigations we determined 96 values of θG as the terminal soil water contents that established themselves when the corresponding water-content waves of preferential flow have practically ceased. We compared the frequency distribution of θG with the one of θ that was calculated from the respective soil hydrological property functions of 32 soil samples that were determined with pressure plate apparatuses in the laboratory. There is support of the notion that θK ≈ θG ≈ θ, thus indicating the potential of θ to explain more generally what constitutes preferential flow. However, the support is assessed as working hypothesis on which to base further research rather than a procedure to a clear-cut identification of preferential flow and associated flow paths. 相似文献