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981.
Biosorption of Cr(VI) using low cost sorbents 总被引:2,自引:0,他引:2
N. Fiol I. Villaescusa M. Martínez N. Miralles J. Poch J. Serarols 《Environmental Chemistry Letters》2003,1(2):135-139
Waste products from industrial operations, such as yohimbe bark, grape stalks, cork and olive stones were investigated for
the removal of Cr(VI) from aqueous solutions. Equilibrium batch experiments at room temperature were performed. Metal uptake
showed a pH-dependent profile and optimum uptake at initial pH between 2.0–3.0. Slight influence of NaCl on metal uptake was
observed. The sorption data fitted well to the Langmuir model within the concentration range studied. Grape stalks proved
to be the most efficient sorbent followed by yohimbe bark, cork and olive stones.
N. Fiol is the recipient of the 2002 ACE Environmental Chemistry Award 相似文献
982.
983.
Wendt?MüllerEmail author Cor?Dijkstra Ton?G.?G.?Groothuis 《Behavioral ecology and sociobiology》2003,55(1):80-86
Hatching asynchrony in avian species leads to age and size differences between nestlings within a brood, handicapping last-hatched chicks in the sibling rivalry. Starvation due to this competitive disadvantage has been regarded as the primary cause of an increase in mortality with hatching order. However, for gulls it has also been suggested that disease is the cause of mortality for last-hatched chicks, possibly through reduced immunocompetence and thereby an enhanced susceptibility to infection. In addition, the male-biased mortality reported for several gull species may be related to a higher vulnerability to diseases in males compared to females. To determine the potential influence of the immune system on these mortality patterns, we investigated the T-cell-mediated immunity (CMI) of black-headed gull chicks in relation to hatching order and sex. We found a significant decrease in the CMI with hatching order. This result may be causally related to systematic changes in maternal yolk steroids and carotenoids within the laying sequence. For second-laid eggs, male CMI was significantly lower than female CMI. This is possibly linked to higher plasma levels of testosterone in male embryos which might have an immunosuppressive effect. If so, this effect is masked in eggs of either high (first egg) or low (last egg) quality. Chicks with low CMI showed enhanced mortality rates. Thus the differences in immune response are likely to contribute to the observed mortality patterns. However, hatching order significantly affected mortality independently of CMI, suggesting that competitive disadvantage due to hatching asynchrony is also important.Communicated by M. Webster 相似文献
984.
Summary. Sequestration of plant toxins in herbivores is often
correlated with aposematic coloration and gregarious behaviour. Larvae
of Pieris brassicae show these conspicuous morphological and behavioural
characteristics and were thus suggested to sequester glucosinolates that
are characteristic secondary metabolites of their host plants. P. rapaeare camouflaged and solitary, and are thus not expected to sequester. To
test this hypothesis and to check the repeatabi-lity of a study that did
report the presence of the glucosinolate sinigrin in P. brassicae,
larvae were reared on three species of Brassicaceae (Sinapis alba,
Brassica nigra and Barbarea stricta), and different leaf and insect
samples were taken for glucosinolate analysis. The major host plant
glucosinolates could only be found in traces or not at all in larval
haemolymph, bled or starved larvae, faeces or pupae of both species or
P. brassicae regurgitant. Haemolymph of both Pieris spp. was not
rejected by the ant Myrmica rubra in dual-choice assays; the regurgitant
of P. brassicae was rejected. This suggests the presence of compounds
other than glucosinolates that might be sequestered in or produced by P.
brassicae only. In faeces of both Pieris spp. a compound which yielded
4-hydroxybenzylcyanide (HBC) upon incubation with sulfatase was detected
in high concentrations when larvae had been reared on S. alba. This
compound may be derived from hydrolysis of sinalbin, the main
glucosinolate of that plant. The unidentified HBC progenitor was
apparently not sequestered in the two Pieris spp., and was not detected
in faeces of larvae reared on B. nigra or B. stricta.
Received 18 July 2002; accepted 11 September 2002. 相似文献
985.
M. Wiens B. Luckas F. Brümmer M. Shokry A. Ammar R. Steffen R. Batel B. Diehl-Seifert H. Schröder W. Müller 《Marine Biology》2003,142(2):213-223
Sponges are sessile filter feeders that are exposed to toxic compounds/xenobiotics and a huge number of diverse pro- and eukaryotic organisms occurring in the aqueous milieu. To cope with these threats, sponges have developed a variety of chemical and immunological defense systems. Among them are potent secondary metabolites or toxins. The demosponge Suberites domuncula contains the bioactive compound okadaic acid; concentrations of ᅢ ng/g (ᅬ nM) of wet tissue have been quantified by LC/MS. In the present study, we sought to determine whether okadaic acid is beneficial for this sponge. Antibodies were raised against okadaic acid and used to localize this compound in situ. It could be demonstrated that the polyclonal antibodies/antiserum stained the sponge cells (endopinacocytes) which form the epithelium of the lacunae and the water channels. They also reacted with bacteria present in sponge tissue. Okadaic acid was found to augment the immune response of S. domuncula against the bacterial endotoxin lipopolysaccharide (LPS). If primmorphs, a special form of 3-D aggregates, are incubated with LPS at a concentration of 3 µg/ml, a reduction in the incorporation rate of [3H] phenylalanine is measured. In the presence of okadaic acid, this effect is measured already at a concentration of 1 µg/ml, suggesting that okadaic acid sensitizes this (immune) response. Okadaic acid is a known inhibitor of protein phosphatases which, as shown here, cause an increased phosphorylation of p38, a central kinase of the MAP kinase pathway; this may explain the sensitive response of the sponge cells to LPS. At higher concentrations, okadaic acid induces apoptosis, as was demonstrated here by a differential expression of the Bcl-2 homolog and the caspase gene. It is concluded that okadaic acid has two functions in the sponge; first, at low concentrations (<100 nM) a stimulation of the defense system against bacteria, and second, at concentrations above 500 nM, a differential effect on the pro-/anti-apoptotic genes. 相似文献
986.
A change in the Si:N ratio of diatom cells during growth was examined for Chaetoceros socialis and Thalassiosira sp., with different initial silicate to nitrate (Si:N) ratios in the media. During exponential growth, C. socialis assimilated silicate and nitrate with a molar ratio of 0.5, independent of the ratio in the media, but after the depletion of nitrate, silicate continued to be taken up, and the Si:N ratio in the stationary phase increased to 2 as a function of the Si:N ratios in the media. In contrast, the ratio of silicate to nitrate taken up by Thalassiosira sp. increased with an increase in the Si:N ratio in the media. The Si:N ratio in the cells during the stationary phase increased in response to an increase in this ratio in the media. The Si:chl a ratio also increased with the increase in the initial Si:N ratio in the media, while the N:chl a ratio did not change to a great extent, indicating the changes in the cellular Si:N ratio was derived from changes in the Si content of the cells. These results indicated that the cellular Si:N ratio changed with the Si:N ratio in the medium, and the Si:N uptake ratio during the growth phase was different depending on diatom species. Thus, the dominance of different diatom species may affect nutrient composition and dynamics in the ocean. 相似文献
987.
Corinna?ThomEmail author David?C.?Gilley Jürgen?Tautz 《Behavioral ecology and sociobiology》2003,53(4):199-205
This study investigates the brief piping signals ("stop signals") of honey bee workers by exploring the context in which worker piping occurs and the identity and behavior of piping workers. Piping was stimulated reliably by promoting a colony's nectar foraging activity, demonstrating a causal connection between worker piping and nectar foraging. Comparison of the behavior of piping versus non-piping nectar foragers revealed many differences, e.g., piping nectar foragers spent more time in the hive, started to dance earlier, spent more time dancing, and spent less time on the dance floor. Most piping signals (approximately 99%) were produced by tremble dancers, yet not all (approximately 48%) tremble dancers piped, suggesting that the short piping signal and the tremble dance have related, but not identical, functions in the nectar foraging communication system. Our observations of the location and behavior of piping tremble dancers suggest that the brief piping signal may (1) retard recruitment to a low-quality food source, and (2) help to enhance the recruitment success of the tremble dance. 相似文献
988.
989.
Goal and Scope
Details about the ecological function of lake shores as ecotones between land and lakes are not well-known. These ecotones are also heavily exploited and, in part, considerably changed. Whereas anthropogenic nutrient loading is decreasing, structural changes are increasing. Unfortunately, there is a deficit in methods of evaluation and decision processes.Main Focus
Even the EU-water framework directive was no remedy for this deficit, as lake shores were included only implicitly. In this article several evaluation methods and their conceptual groundwork are presented. However, these methods were not developed for lake shore research. Therefore, criteria are proposed which could fulfill the specific demands of lake shore assessments. The management of lakes shores should consider structural and biological parameters, and be agreeable to local residents.Results and Conclusions
In addition to conventional biodiversity methods, the ecology of lake shores could also be represented by a functional food net, for example in benthic invertebrates. But even quantification of biodiversity alone creates many problems. A simple biodiversity index cannot meet all the demands placed on a method of evaluation in complex situations, especially when coupled with additional information on structure, practicability, costs, etc. For these reasons, assessments for future management cannot be based on such an index.Outlook
A possible approach to include this complexity in assessments is to apply mathematical models and theoretical order concepts. 相似文献990.
This paper describes a study of the treatment of surfactant synthetic solutions by chemical and photolytic oxidation. Synthetic solutions of linear alkylbenzene sulfonates (LAS) are treated in this work as this is a model compound commonly used in the formulation of detergents, with a great presence in urban and industrial waste-waters. The application of ultraviolet (UV) radiation combined with hydrogen peroxide to oxidize linear alkylbenzene sulfonates (LAS) is shown to be suitable as a primary oxidation step since conversions of about 50% of the original compounds are achieved in the most favorable cases. Initially, the influence of the operating variables on the degradation levels is analyzed in this work. A kinetic model that considers the contributions of both direct photolysis and radical attack is also worked out. Direct photolysis is performed to determine the quantum yield in the single photodecomposition reaction. In addition, the rate constant of the reaction between hydroxyl radicals and linear alkylbenzene sulfonates in the oxidizing system H2O2/UV is determined for different operational conditions. Finally, the contribution of each oxidation pathway is quantified, resulting in a higher contribution of the radical reaction than of photolysis in all cases. 相似文献