Cadmium leaching from micro-lysimeters planted with the hyperaccumulator Thlaspi caerulescens: experimental findings and modeling

The use of heavy metal hyperaccumulating plants has the potential to become a promising new technique to remediate contaminated sites. We investigated the role of metal mobilization in the Cd hyperaccumulation of Thlaspi caerulescens (J. & C. Presl, 'Ganges'). In a micro-lysimeter experiment we investigated the dynamics of Cd concentration of leachate as well as Cd removal by plant uptake in four treatments: (i) Control (bare soil), (ii) T. caerulescens, (iii) nonhyperaccumulator Brassica juncea (L.) Czern. ('PI 426308'), and (iv) co-cropping of the hyperaccumulator and nonhyperaccumulator. The experimental findings were analyzed using one- and two-site rate-limited desorption models. Co-cropping of T. caerulescens and B. juncea did not enhance metal uptake by B. juncea. Although Cd uptake of T. caerulescens was 10 times higher than that of B. juncea, the Cd concentration of leachate of the T. caerulescens treatment did not decrease below that of the B. juncea treatment. The Cd depletion in leachate was well reproduced by the two-site rate-limited desorption model. The optimized desorption coefficient was three orders of magnitude higher in the rhizosphere than in the bulk soil. Our results indicate that T. caerulescens accelerates the resupply of Cd from soil pointing to an important role of kinetic desorption in the hyperaccumulation by T. caerulescens.     

Genotoxic effects of Ag2S and CdS nanoparticles in blue mussel (Mytilus edulis) haemocytes

The use of functionalised metal sulphide nanoparticles (NPs) for nanoremediation and biomedical application is rapidly increasing, which could lead to significant inputs into the marine environment. The potential impact of some NPs on marine organisms is still poorly understood. In the present paper the genotoxic potential of Ag₂S and CdS NPs on Mytilus edulis haemocytes was assessed. MPEG-SH (thiol-terminated methyl polyethylene glycol), was used as capping agent to avoid NPs agglomeration. TEM analysis showed that the Ag₂S NPs size was 13±7 nm, whereas CdS quantum dots had an average diameter of 4±1 nm. DNA integrity was evaluated by Comet assay following exposure to increasing concentration series (0.01–10 mg/L). Both silver and cadmium NPs showed genotoxic effects at the highest dose. MPEG-SH was also found to exert a weak genotoxic activity, suggesting that at least part of the genotoxic potential of functionalised NPs on mussel cells might be attributable to the capping agent. These results confirm the genotoxic potential of Ag₂S NPs for mussel cells and demonstrated, for the first time, that CdS NPs is genotoxic in a marine organism.     

瑞典森林中不同地区的林下植被情况与氮沉积的关系

在557块针叶林分中进行调查,以图了解欧洲越桔(Vacciniummyrtillus)、越桔(V.vitis-idaea)和曲芒发草(Deschampsiaflexuosa)与氮沉积率的相互联系.欧洲越桔在高氮地区比在低氮地区发生频度、丰富度都较少并且易感染叶部病原(Valdensiaheterodoxa),越桔的发生与氮沉积的增加呈明显的负相关,曲芒发草却没有这种趋势.在高氮沉积地区,欧洲越桔在优势种为欧洲赤松的林分中比在挪威云杉为优势种的林分中更为最普遍.在氮沉积较低水平的地区不是这种情形.调查的情况与增施氮素实验的结果一致,氮沉积对植被显示了巨大的效应.数据表明即使是较低的氮沉积也可能减少针叶林分林下植被最优势种的丰富度.     

Die Bestimmung der Herkunft der Marmore von Büsten der Münchener Residenz

51 Greek, Roman and Renaissance marble busts from the Antiquarium of the Residenz in Munich were studied for their C- and O-isotopic composition. Apart from some overlapping values, this technique permits — contrary to microscopic and chemical methods — localization of different Turkish, Greek and Italian marble deposits.     

Urknall und Evolution des Kosmos

The Science of Nature -     

Divergent evolution of feeding substrate preferences in a phylogenetically young species flock of pupfish (Cyprinodon spp.)

A fundamental question in sympatric speciation is how trophic divergence is achieved. We used an extremely young (<8,000 years) species flock of pupfish (Cyprinodon spp.) from Laguna Chichancanab in south-eastern Mexico to examine divergent evolution of preferences for different feeding substrates. In a test aquarium, we presented four feeding substrates (sand, gravel, a plastic plant, and blank bottom), but no actual food was offered. The four feeding substrates were chosen to mirror the most common substrate types in Laguna Chichancanab. Previous studies demonstrated that benthic food items prevail in the diet of most Cyprinodon species. C. beltrani preferred sand, whereas C. labiosus preferred gravel. F₁ hybrids of both species showed intermediate preferences. C. maya searched for food equally at all substrates. As the test fish were reared under identical laboratory conditions (i.e., in the absence of feeding substrates), the species-specific preferences appear to be genetically fixed, suggesting rapid divergent evolution of feeding behaviors.     

Short-Term Opportunities for Decreasing CO2 Emissions from the Steel Industry

There is a strong political will to decrease CO₂ emissions. Although the steel industry only accounts for some 5% of worldwide CO₂ emissions (which totalled 1,200 million tonnes per annum in the late 1990s), it will be strongly affected by this. The EU, for example, is putting up strong economic incentives for reductions. This is taking place at a time when demand for steel products is greater than ever. To radically change existing processes and production routes to decrease the CO₂ emissions would be extremely expensive, even if it were possible. Nevertheless, many of the solutions which have been discussed seem to go in this direction. The other alternative discussed seems to be the creation of process solutions and alterations that lead to a focusing of CO₂ streams, i.e., much higher CO₂ concentrations in flue gases than today, for entrapment of the CO₂ so that it is not discharged into the atmosphere. These solutions are feasible, but expensive.

However, there exists today a number of solutions and technologies which, if fully implemented, could substantially decrease CO₂ emissions without seriously altering current methods of operation; they are short-term viable solutions. The present paper reviews and discusses such technologies, throughout the steel production paths. If these solutions are fully implemented, the combined impact on CO₂ emissions from the steel industry worldwide is estimated to be a reduction of 100–150 million tonnes of CO₂ per annum, i.e., current emissions can be reduced by some 8–10% within a relatively short time span.