Metallsorption an Illit und Metallfreisetzung unter Einwirken der Aminosäuren Glycin und Histidin

The heavy metal ions Zn(II), Pb(II), Cr(III) and Hg(II) were examined in regard of their adsorption behaviour towards Kaolin W from Lohrheim (51% illite, 31% kaolinite and 18% quarz). By means of the Langmuir and Freundlich models the determined adsorption isothermes could be linearized. The ability of glycine and histidine solutions to release heavy metal ions, pre-adsorbed on Kaolin W (36,1–2300 mg kg^?1 Zn, Pb, Cr and Hg), was specified. It was found a low influence of glycine, but an evident influence of histidine to the metal release, expecially of Pb and Cr, depending on the metalcoating, metal-amino acid-ratio, experimental pH and testing period. The highest remobilisation fraction, up to 98%, could be found in the case of Zn. This elucidates an enhancement of the zinc release compared with the blank solution, without containing amino acids, to a factor of maximal 9,3. As far as Pb and Cr were concerned the histidine extraction exeeded the remobilisation in the blank solution by a maximum of 50,8 or 40. As Hg develops strong covalent bondings to illite by OH-bridges, the release of Hg was not affected by the amino acids.     

Evolutionary aspects of perfume collection in male euglossine bees (Hymenoptera) and of nest deception in bee-pollinated flowers

Summary A fascinating pollination system has been evolved between perfume producing flowers and perfume collecting male euglossine bees in the neotropics. Detailed investigations have contributed to an understanding of the interactions between euglossine males and flowers as a pollination system. The role which the collected perfume plays in the reproductive behaviour of euglossine bees is not fully understood. A favoured hypothesis suggests that the collected fragrances are used as precursors for male sex pheromones and thus serve to attract conspecific males or females. It is not known how perfume collection behaviour evolved. Here, an evolutionary approach presents a new hypothesis which suggests that the evolution of perfume collection in euglossine males is based upon pre-existing signals which were attractive to females and males. It is further suggested that, at the evolutionary outset, flowers mimicked nest sites to deceive nest-seeking euglossine bees. In addition, a comparative study was undertaken on the phenomena of nest-mimicking flowers in related bee families.     

Input of trichloroacetic acid into the vegetation of various climate zones--measurements on several continents

Trichloroacetic acid (TCA, CCl(3)COOH) is a phytotoxic chemical. Although TCA salts and derivates were once used as herbicides to combat perennial grasses and weeds, they have since been banned because of their indiscriminate herbicidal effects on woody plant species. However, TCA can also be formed in the atmosphere. For instance, the high-volatile C(2)-chlorohydrocarbons tetrachloroethene (TECE, C(2)Cl(4)) and 1,1,1-trichloroethane (TCE, CCl(3)CH(3)) can react under oxidative conditions in the atmosphere to form TCA and other substances. The ongoing industrialisation of Southeast Asia, South Africa and South America means that use of TECE as solvents in the metal and textile industries of these regions in the southern hemisphere can be expected to rise. The increasing emissions of this substance--together with the rise in the atmospheric oxidation potential caused by urban activities, slash and burn agriculture and forest fires in the southern hemisphere--could lead to a greater input/formation of TCA in the vegetation located in the lee of these emission sources. By means of biomonitoring studies, the input/formation of TCA in vegetation was detected at various locations in South America, North America, Africa, and Europe.     

Environmental risks of chemicals and genetically modified organisms: A comparison

Risks can be characterised by several parameters. A risk is commonly defined to be the product of the extent of damage and the probability of its occurrence. But there are several other characteristics to be taken into account: degree of certainty in determining extent and probability, persistency, ubiquity, irreversibility, delay effect and mobilisation potential. As potential risks of genetically modified plants (GMPs), resistance to antibiotics, impact on non-target organisms, spread of genes and GMOs, and secondary consequences, e.g. on cultivation practice, are discussed in detail. Risks of GMPs are, in general, characterised by high uncertainty of the magnitude and probability of damage, a high mobilisation potential and a delay effect.     

Nachhaltige Chemie

Ohne Zusammenfassung     

The Rossby Centre Regional Atmospheric Climate Model part II: application to the Arctic climate

The Rossby Centre regional climate model (RCA2) has been integrated over the Arctic Ocean as part of the international ARCMIP project. Results have been compared to observations derived from the SHEBA data set. The standard RCA2 model overpredicts cloud cover and downwelling longwave radiation, during the Arctic winter. This error was improved by introducing a new cloud parameterization, which significantly improves the annual cycle of cloud cover. Compensating biases between clear sky downwelling longwave radiation and longwave radiation emitted from cloud base were identified. Modifications have been introduced to the model radiation scheme that more accurately treat solar radiation interaction with ice crystals. This leads to a more realistic representation of cloud-solar radiation interaction. The clear sky portion of the model radiation code transmits too much solar radiation through the atmosphere, producing a positive bias at the top of the frequent boundary layer clouds. A realistic treatment of the temporally evolving albedo, of both sea-ice and snow, appears crucial for an accurate simulation of the net surface energy budget. Likewise, inclusion of a prognostic snow-surface temperature seems necessary, to accurately simulate near-surface thermodynamic processes in the Arctic.     

Chemische Reaktionen von Phenylarsinverbindungen

Zusammenfassung  Phenylarsindichlorid (PFIFFIKUS) reagiert bei Raumtemperatur in einer Gleichgewichtsreaktion schnell mit Alkoholen unter Bildung von Phenylarsinbisether und Phenylarsinchloridether. Die Reaktionen verlaufen nicht quantitativ. Die Derivate wurden massenspektrometrisch identifiziert.