New highly fluorinated monodentate and bidentate phosphine oxide compounds of the type {CF(3)(CF(2))(n)CH(2)CH(2)}(3)PO (n = 5, 9) and [{CF(3)(CF(2))(5)CH(2)CH(2)}(2)P(O)CH(2)CH(2)P(O){CH(2)CH(2)(CF(2))(5)CF(3)}] have been prepared. Their ability to extract a number of metals and radionuclides from aqueous solutions into perfluorinated solvents has been established and the extractable species investigated. All extractants extract the metals As(V), Cd(II), Co(II), Cr(VI), Hg(II), Pb(II), and Sn(II) with >75% removal. In addition, the radioisotopes (90)Sr(II), (133)Ba(II), and U(VI) have been investigated, whilst (59)Fe(III) has been used to model the extraction of plutonium. (133)Ba(II) shows a high distribution ratio for monodentate phosphine oxides, whilst for UO(2)(2+) and (59)Fe(III) bidentate phosphine oxides are superior. 相似文献
Contamination by 2,4,6-trinitrotoluene (TNT) is a global environmental problem at sites of former explosive production, handling, or storage, and could have deleterious consequences for human and ecological health. We investigated its sublethal effects to Eisenia fetida, using two nonspecific biomarkers. In coelomocytes of earthworms exposed 24, 48, or 72 h, we evaluated DNA damage (comet assay) and neutral red retention time (NRRT), using the filter paper contact test. Both percentage of damage (D%) and calculated damage index showed significant DNA damage at almost all concentrations, at all time points assayed. Along exposure time, two different patterns were observed. At the lower TNT concentrations (0.25?C0.5 ??g/cm2) an increased DNA migration at 48 h, with a decrease close to initial levels after 72 h exposure, was observed. This decrease could be attributed to activation of the DNA repair system. At higher concentrations (1.0?C2.0 ??g/cm2), the high DNA damage observed remained constant during the 72 h exposure, suggesting that the rate of DNA repair was not enough to compensate such damage. Analysis of NRRT results showed a significant interaction between time and treatment. After 48 h, a significant decrease was observed at 4.0 ??g/cm2. After 72 h, NRRT presented a concentration-dependent decrease, significantly different with respect to control at 0.5, 1.0, 2.0, and 4.0 ??g/cm2. The two assayed methods, performed on the same sample, showed clear responses to sublethal TNT exposure in E. fetida, providing sensitive unspecific biomarkers of cell injury and DNA damage. 相似文献
Humic substances, in aqueous bodies primarily fulvic acids, may demonstrate an inhibitory as well as an activating influence on organisms. We present evidence with bacteria-containing algal cultures and with cultures of the nematodeCaenorhabditis elegans. Structural elements of the fulvic acids which may be responsible for such effects are not yet known. Furthermore, the presence of fulvic acids may lead to increases in bioconcentration of xenobiotics. Increase in the toxicity of xenobiotics in the presence of humic substances have also been described. We present studies applying lethal as well as sublethal toxicity endpoints. 相似文献
As financing protection against mountain hazards becomes increasingly challenging and therefore investments have to be prioritized, dilemmas of justice emerge: some local governments and individuals benefit from natural hazard protection schemes, whereas others loose. Decisions on whom to protect often caused contradicting concepts of political understanding, which differ in interpretations of fair resource allocation and distribution. This paper analyses the impact of different philosophical schools of social justice on mountain hazard management in Austria. We used data from a spatially explicit, object-based assessment of elements at risk and compared potential distributional effects of three political jurisdictions. We found that—depending on the respective political direction—various local governments gain and others loose within the actual distributional system of mitigation strategies. The implementation of a utilitarian policy approach would cause that high income communities in hazard-prone areas would mainly benefit. Consequently, this policy direction would encourage the public administration to ignore their own failure in the past natural hazards management and prevention. On the other hand, following a Rawlsians approach mainly peripheral communities would gain from new policy direction who often show besides natural hazards problem mainly large socio-economic challenges. Finally, the most radical change would include the implementation of a liberalism policy, whereabouts the state only provides hazard information, but no further mitigation measures. These findings highlight the distributional consequences of future mountain hazard management strategies and point to the crucial selection of policy direction in navigating the selection of various adaptation schemes.
For higher plant tests in hydroculture we developed a method to unify the usually separately performed germination and growth testing. This method renders unnecessary the time-consuming and laborious installation of the germinated plants into the growth system. 相似文献
Estimates of the global carbon sink induced by nitrogen enrichment range vary widely, from nearly zero to 2.3 Gt C year?1. It is necessary to reduce this uncertainty if we are to make accurate predictions of the future magnitude of the terrestrial carbon sink. Here, we present a Monte Carlo approach to uncertainty and sensitivity analysis of three ecosystem models, Century, BGC and Hybrid. These models were applied to a coniferous forest ecosystem in Sweden. The best estimate of the change in total carbon content of the ecosystem with the cumulative change in nitrogen deposition over 100 years, ΔCtotal/ΔNdeposition was 20.1 kg C (kg N)?1 using the pooled mean, with a pooled standard deviation of 13.8 kg C (kg N)?1. Variability in parameters accounted for 92% of the total uncertainty in ΔCtotal/ΔNdeposition, and only 8% was attributable to differences between models. The most sensitive parameters were those which controlled the allocation of assimilate between leaves, roots and stem. In particular, an increase in allocation to fine roots led to a large reduction in ΔCtotal/ΔNdeposition in all models, because the fine roots have a very high turnover rate, and extra carbon allocated there is soon lost through mortality and decomposition. 相似文献
The nest of the dwarf honeybee A. florea Fabr. consists of a single comb attached to a tree branch. Recruitment dances take place on the upper surface of the comb
that must therefore be kept clear of debris. We report here, for the first time, a behaviour that serves for removing leaves
and other foreign objects from the surface of the comb. Individual workers crawl under the object and lift it with their heads,
pushing it towards the rim where it eventually slides off the comb. Objects that are heavier or fixed at one end such as leaves
are nevertheless lifted and kept away from the surface for up to several minutes. This "head-pushing" is frequently performed
without the aid of mandibles, and individuals performing it maintain a distinctive posture, holding the forelegs at an angle
without touching the object. Repeated involvement of particular individuals indicate that head-pushers might form a distinct
task group.
Received: 24 November 1999 / Accepted in revised form: 10 March 2000 相似文献