Antimony uptake by <Emphasis Type="Italic">Zea mays</Emphasis> (L.) and <Emphasis Type="Italic">Helianthus annuus</Emphasis> (L.) from nutrient solution

We investigated the extent of Sb uptake by maize (Zea mays) and sunflower (Helianthus annuus) from nutrient solutions containing concentrations from 3 to 24 mg/L of potassium antimonate, with the aim of determining the potential of Sb to enter the food chain. The maximum shoot Sb concentrations in Z. mays and H. annuus were 41 mg/kg and 77 mg/kg dry weight, respectively. There was no significant difference in Sb uptake between species. The average bioaccumulation coefficients (the plant/solution concentration quotients) were 1.02 and 1.93 for Z. mays and H. annuus, respectively. Phosphate addition did not affect plant growth or Sb uptake. Antimony uptake by both Z. mays and H. annuus is unlikely to pose a health risk to animals and humans.     

Pharmazeutisch aktive Substanzen in kleinen Fließgewässern

Background

Current hydrological research is increasingly focusing on pharmaceutically active compounds (PhACs). Concerning the issue of quality of drinking water, this problem has also become the focus of public interest. However, in spire of the fact that the fate of chemicals in surface waters has been assessed in great detail, the influence of groundwater-exchange is yet only little known.

Goal

This study gives emphasis to the question of how transport and degradation of PhACs interact with the exchange of surface water with groundwater. Special interest is given to alternating groundwater regimes.

Methods

Based on a small stream system in the north of Berlin, Germany, a one-dimensional compartment-model was established using differential mass-balance. The stream which, at its mouth, discharges 0.3 m³ s^?1 is already well investigated and thus provides a good empirical data basis. The processes taken into account by the model were ‘exchange of surface-water with groundwater’, ‘decomposition’ as well as ‘transport’ of PhACs. Calculations were performed using the commonly used analgesic Diclofenac as an example and defining 81 scenarios by different groundwater regimes. Hasse Diagramm Technique was used to compare the scenarios.

Results

All scenarios show a big influence of groundwater-exchange to the fate and concentration of PhACs in surface waters. In the case of the modelled stream system, dilution by groundwater was more responsible for a decrease in concentration than degradation was. Furthermore, on the background of a standard scenario, the loss due to groundwater by 5.4 percent was in the same magnitude as the loss due to decomposition (9.7 percent). A crucial difference between punctual versus linear afflux of groundwater has not been observed.

Discussion

The alteration of discharge resulted in a big influence of the case differentiation between ‘constant velocity’ and ‘constant cross-section’. Furthermore, the model was based on the assumption that groundwater was unloaded with PhACs or diluted very well in comparison to the stream. In contrast, regarding measurements in the catchment, groundwater could even be a diffuse source of the contamination of the stream.

Conclusions

The fate of PhACs in our model is crucially driven by interactions with groundwater. Therefore, assessing the risk emanating from substances like Diclofenac, it is very important to regard their accessibility to decomposition as well as the morphology of the stream-system and its interactions with the groundwater.

Perspectives

In this model, the process of transport from the surface to groundwater back to the surface was dealt with insufficiently; in order to be able to observe fully developed interaction in a further step of modelling, a groundwater-transportmodel should be coupled completely with a surface-water-model.     

TNT in Komposten und Flüssigkultur

The formation of aromatic amines was investigated using a summarized test (NEDA-test) during the composting of 2,4,6-trinitrotoluene (TNT) contaminated soil. In this test, the aromatic amines were diazolated and then coupled to N-1-Naphthyl-ethylenediamine-dihydrochloride (NEDA) to yield an azo dye which can be monitored photometrically. The test was calibrated for known TNT-metabolites with an active amine-group. Liquid samples from composting- and liquid-culture-experiments were analyzed by HPLC for these known metabolites. Moreover, the samples were monitored by the NEDA-test and the expected extinction of the TNT-metabolites found with amine function were extrapolated with the help of calibration curves. It was shown that substantial differences are obvious between the monitored and extrapolated values. After separation into polar and non-polar aromatic amines, it became clear that these differences are made by the polar aromatic amines. Polar aromatic amines, which are not detectable by presently available analytical tests, were generated during the composting of TNT-contaminated soils. Contaminated stagnant water, which was generated during anaerobization of a compost prephase, was treated aerobically for 70 days in a biofermenter. During this treatment TNT and its known metabolites were eliminated almost entirely. Simultaneously, the toxicity in the Lumis Tox-test decreased drastically. In striking contrast, the sum of aromatic amines decreased only to a minor extent. Moreover, the percentage of polar compounds from total amount of aromatic amines increased drastically from 48% to more than 95%. At present, the chemical identification of these polar compounds is still missing and is the object for further research.     

International trade in biofuels: an introduction to the special issue

Currently, many countries are establishing goals for substituting biofuels for fossil fuels. These goals usually foresee 5–10% substitution while today's production, in most countries, is far below 2%. Evidently, many countries will seek to meet their ambitious biofuel targets through imports. This global trade in biofuels, which is to some extent already taking place, will have a major impact not only on other commodity markets like vegetable oils or animal fodder but also on the global land use change and on environmental impacts. This special issue focuses on the relation between trading, policy making and sustainability impacts of biofuels. It demonstrates the strong but complex link between biofuels production and the global food market, it unveils policy measures as the main drivers for production and use of biofuels and it analyzes various sustainability indicators and certification schemes for biofuels with respect to minimizing the adverse effects of biofuels while maximizing the benefits of the future use of biofuels.     

Non-specific association between filamentous bacteria and fungus-growing ants

Fungus-growing ants and their fungal cultivar form a highly evolved mutualism that is negatively affected by the specialized parasitic fungus Escovopsis. Filamentous Pseudonocardia bacteria occurring on the cuticle of attine ants have been proposed to form a mutualistic interaction with these ants in which they are vertically transmitted (i.e. from parent to offspring colonies). Given a strictly vertical transmission of Pseudonocardia, the evolutionary theory predicts a reduced genetic variability of symbionts among ant lineages. The aim of this study was to verify whether actinomycetes, which occur on Acromyrmex octospinosus leaf-cutting ants, meet this expectation by comparing their genotypic variability with restriction fragment length polymorphisms. Multiple actinomycete strains could be isolated from both individual ant workers and colonies (one to seven strains per colony). The colony specificity of actinomycete communities was high: Only 15% of all strains were isolated from more than one colony, and just 5% were present in both populations investigated. Partial sequencing of 16S ribosomal deoxyribonucleic acid of two of the isolated strains assigned both of them to the genus Streptomyces. Actinomycetes could also be isolated from workers of the two non-attine ant species Myrmica rugulosa and Lasius flavus. Sixty-two percent of the strains derived from attine ants and 80% of the strains isolated from non-attine ants inhibited the growth of Escovopsis. Our data suggest that the association between attine ants and their actinomycete symbionts is less specific then previously thought. Soil-dwelling actinomycetes may have been dynamically recruited from the environment (horizontal transmission), probably reflecting an adaptation to a diverse community of microbial pathogens.