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131.
Bossew P Gastberger M Gohla H Hofer P Hubmer A 《Journal of environmental radioactivity》2004,73(1):87-99
Five soil profiles from a site about 8 km SE of the Chernobyl NPP were investigated for the vertical distribution of radionuclides. The average (137)Cs-inventory at the site is about 2.6 MBq/m(2) (reference date 1 May 1986). Apart from (137)Cs, the following radionuclides have been identified (their activity ratios to (137)Cs in brackets): (134)Cs (0.537), (125)Sb (0.068), (60)Co (0.0022), (154)Eu (0.016), (155)Eu (0.020), (94g)Nb (9.5E-5), (239/240)Pu (0.0088), (238)Pu (0.040), (90)Sr (0.30) and (241)Am (0.011). Apparent vertical migration velocities are between 0.14 and 0.26 cm/a, apparent dispersion coefficients range from 0.02 to 0.13 cm(2)/a. The rankings of the velocities v for different radionuclides are (Sr, Cs, Sb, Co, Pu)< Am < Eu and Sr < (Cs, Nb), for D, the following rankings have been found: (Nb, Sr, Cs) < Am < Eu, Cs相似文献
132.
Lin Z Comet B Qvarfort U Herbert R 《Environmental pollution (Barking, Essex : 1987)》1995,89(3):303-309
Recently investigations have shown that the annual flux of lead from shotgun pellets to shooting range soils is significant in some countries. This paper presents the data of chemical and mineralogical analyses of soils and Pb-pellet crusts from five shooting ranges in Sweden and, based on these results, evaluates the retention of lead in these shooting range soils. In the soils, Pb-pellets and bullets are readily decomposed and transformed to crust materials composed of Pb-bearing minerals. The transformation products in the crust materials, identified by X-ray diffraction, are predominantly hydrocerussite [Pb(3)(CO(3))(2) (OH)(2)], associated with cerussite (PbCO(3)) and anglesite (PbSO(4)). In a period of 20-25 years, an average of 4.8% metallic lead in the pellets has been transformed to lead carbonate and lead sulphate, where the former is the more stable mineral in the surface environment. However, in soils relatively rich in humus an average of 15.6% metallic lead in the pellets was transformed to secondary lead compounds in the same period. The results of the chemical analyses indicate that Pb is rather immobile in the soil profile. The surficial horizon contains higher concentrations of lead (52-3400 mg kg(-1)), while lower concentrations of lead were found in the E and B horizons where the total Pb concentrations (8-37 mg kg(-1)) are within about one standard deviation of the mean reference sample concentration. An inverse relationship is revealed between the aluminium hydroxide content of the soil fraction and EDTA-extractable Pb, which suggests that these compounds have affected the retention of lead. 相似文献
133.
Jerome M Diamond Andrew D Eaton Clifford Annis Rock Vitale Herbert J Brass 《Water environment research》2007,79(2):208-214
The choice of wastewater compliance methods used in the United States has been largely prescribed; however, in some cases, this has led to data of unknown or poor quality. This problem is further compounded by the relatively slow regulatory approval process to incorporate discharge-specific method modifications or flexibility to using alternate, potentially better technologies. In this study, a framework is presented, using a performance-based-system approach, which a discharger could use to verify proper use of an alternate or modified method. An example, using two chemical oxygen demand methods (a currently approved method and an alternate method that does not generate hazardous waste) demonstrates that the protocol is simple to use, yet scientifically defensible and effective and that this approach should be readily understandable to both regulators and the regulated community. Our results also suggest that the reference method approach, without associated measurement quality objectives, may yield a false sense of competency with an alternate method. 相似文献
134.
During irradiation of aqueous solutions of a mixture of oligomeric dimethylsiloxanes with artificial sunlight in the presence of nitrate ions, a reduction in the concentration of the siloxanes was demonstrated. This was verified by atomic absorption spectroscopy and proton nuclear magnetic resonance spectroscopy.In two separate tests, average halflives of 9 and 4 days, respectively, were determined after extraction of the aqueous solutions and analysis by atomic absorption spectroscopy.Silicate was demonstrated to be the final photodegradation product of these water soluble siloxanes. Photometric determination of silicate after 35 days showed nearly complete transformation, based on the original quantity of siloxanes.When an aqueous emulsion of high molecular-weight poly(dimethylsiloxane) was irradiated in the presence of nitrate ions under similar experimental conditions, a level of silicate corresponding to 1.7% of the original quantity of poly(dimethylsiloxane) was found after 5 weeks. 相似文献
135.
Resprouting is an important persistence strategy for woody species and represents a dominant pathway of regeneration in many plant communities, with potentially large consequences for vegetation dynamics, community composition, and species coexistence. Most of our knowledge of resprouting strategies comes from fire-prone systems, but this cannot be readily applied to other systems where disturbances are less intense. In this study we evaluated sapling responses to stem snapping for 49 moist-forest species and 36 dry-forest species from two Bolivian tropical forests. To this end we compared in a field experiment the survival and height growth of clipped and control saplings for a two-year period, and related this to the shade tolerance, carbohydrate reserves, and the morphological traits (wood density, leaf size) of the species. Nearly all saplings resprouted readily after stem damage, although dry-forest species realized, on average, a better survival and growth after stem damage compared to moist-forest species. Shade-tolerant species were better at resprouting than light-demanding species in moist forest. This resprouting ability is an important prerequisite for successful regeneration in the shaded understory, where saplings frequently suffer damage from falling debris. Survival after stem damage was, surprisingly, only modestly related to stem reserves, and much more strongly related to wood density, possibly because a high wood density enables plants to resist fungi and pathogens and to reduce stem decay. Correlations between sampling performance and functional traits were similar for the two forest types, and for phylogenetically independent contrasts and for cross-species analyses. The consistency of these results suggests that tropical forest species face similar trade-offs in different sites and converge on similar sets of solutions. A high resprouting ability, as well as investments in stem defense and storage reserves, form part of a suite of co-evolved traits that underlies the growth-survival trade-off, and contributes to light gradient partitioning and species coexistence. These links with shade tolerance are important in the moist evergreen forest, which casts a deep, more persistent shade, but tend to diminish in dry deciduous forest where light is a less limiting resource. 相似文献
136.
Attila?HettyeyEmail author Balázs?Vági János?T?r?k Herbert?Hoi 《Behavioral ecology and sociobiology》2012,66(2):201-208
The theory of life history evolution assumes trade-offs between competing fitness traits such as reproduction, somatic growth,
and maintenance. One prediction of this theory is that if large individuals have a higher reproductive success, small/young
individuals should invest less in reproduction and allocate more resources in growth than large/old individuals. We tested
this prediction using the common toad (Bufo bufo), a species where mating success of males is positively related to their body size. We measured testes mass, soma mass, and
sperm stock size in males of varying sizes that were either (1) re-hibernated at the start of the breeding season, (2) kept
without females throughout the breeding season, or (3) repeatedly provided with gravid females. In the latter group, we also
estimated fertilization success and readiness to re-mate. Contrary to our predictions, the relationship between testes mass
and soma mass was isometric, sperm stock size relative to testes mass was unrelated to male size, fertilization success was
not higher in matings with larger males, and smaller males were not less likely to engage in repeated matings than larger
males. These results consistently suggest that smaller males did not invest less in reproduction to be able to allocate more
in growth than larger males. Causes for this unexpected result may include relatively low year-to-year survival, unpredictable
between-year variation in the strength of sexual selection and low return rates of lowered reproductive investment. 相似文献
137.
138.
139.
E. Lamla Egon Ullrich E. Wicke H. Hellmann Herbert Förster 《Die Naturwissenschaften》1956,43(10):235-236
140.