Preferences for different nitrogen forms by coexisting plant species and soil microbes

The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different chemical forms of N. In this study, we used in situ stable isotope labeling techniques to assess whether coexisting plant species of a temperate grassland (England, UK) display preferences for different chemical forms of N, including inorganic N and a range of amino acids of varying complexity. We also tested whether plants and soil microbes differ in their preference for different N forms, thereby relaxing competition for this limiting resource. We examined preferential uptake of a range of 13C15N-labeled amino acids (glycine, serine, and phenylalanine) and 15N-labeled inorganic N by coexisting grass species and soil microbes in the field. Our data show that while coexisting plant species simultaneously take up a variety of N forms, including inorganic N and amino acids, they all showed a preference for inorganic N over organic N and for simple over the more complex amino acids. Soil microbes outcompeted plants for added N after 50 hours, but in the long-term (33 days) the proportion of added 15N contained in the plant pool increased for all N forms except for phenylalanine, while the proportion in the microbial biomass declined relative to the first harvest. These findings suggest that in the longer-term plants become more effective competitors for added 15N. This might be due to microbial turnover releasing 15N back into the plant-soil system or to the mineralization and subsequent plant uptake of 15N transferred initially to the organic matter pool. We found no evidence that soil microbes preferentially utilize any of the N forms added, despite previous studies showing that microbial preferences for N forms vary over time. Our data suggest that coexisting plants can outcompete microbes for a variety of N forms, but that such plant species show similar preferences for inorganic over organic N.     

Benzyl-penicillin (Penicillin G) transformation in aqueous solution at low temperature under controlled laboratory conditions

Antibiotics are released into the environment in a variety of ways: via wastewater effluent as a result of incomplete metabolism in the body after use in human therapy, as runoff after use in agriculture, through improper disposal by private households or hospitals or through insufficient removal by water treatment plants. Unlike in most European countries, in Arctic regions effluents are not suitably treated prior to their release into the aquatic environment. Also, many of the scattered human settlements in remote regions of the Arctic do not possess sewage treatment facilities and pharmaceutical residues therefore enter the aqueous environment untreated. Only limited data are available on the biodegradation of antibiotics under Arctic conditions. However, such information is needed to estimate the potential harm of antibiotics for the environment. Pen-G is used in this study since it is a widely prescribed antibiotic compound whose environmental properties have not yet been investigated in detail. Thus, for a very first assessment, the OECD approved biodegradation Zahn-Wellens test (ZWT, OECD 302 B) was used to study biodegradation and non-biotic elimination of the antibiotic Benzyl-penicillin (Pen-G) at different temperatures (5°C, 12.5°C and 20°C). The testing period was extended from the OECD standard of 28-42d. In addition to dissolved organic carbon (DOC), Pen-G levels and major transformation products were recorded continuously by LC-ion-trap-MS/MS. DOC monitoring revealed considerable temperature dependence for the degradation process of Pen-G. DOC loss was slowest at 5°C and considerably faster at 12.5°C and 20°C. In the initial step of degradation it was found that Pen-G was hydrolyzed. This hydrolyzed Pen-G was subsequently further degraded by decarboxylation, the result of which was 2-(5,5-dimethyl-1,3-thiazolidin-2-yl)-2-(2-phenylacetamido)acetic acid. Furthermore, direct elimination of 2-phenyl-acetaldehyde from the hydrolyzed and decarboxylated Pen-G also led to the formation of 2-[amino(carboxy)methyl]-5,5-dimethyl-1,3-thiazolidone-4-carboxylic acid. Since biodegradation slows down considerably at a low temperature, the resulting transformation products had considerably longer residence times at 5°C compared to higher temperature conditions within the 42-d experiment. The results presented here clearly demonstrate that a risk assessment for pharmaceuticals present in low ambient temperature environments (i.e. the Arctic) cannot be based on test results obtained under standard laboratory conditions (i.e. 20°C ambient temperatures).     

An Automated Technique for Delineating and Characterizing Valley-Bottom Settings

Accurate delineation and characterization of valley-bottom settings is crucial to the assessment of the biological and geomorphological components of riverine systems; yet, to date, most valley-bottom mapping endeavors have been done manually. To improve this situation, we developed automated techniques in a Geographic Information System (GIS) for delineating and characterizing valley-bottom settings in river basins ranging in size from approximately 1,000–10,000 km². All procedures were developed with ARC/INFO GIS software and fully automated in Arc Macro Language (AML). The GRID module is required for valley-bottom delineation and slope calculations; whereas characterization (i.e., measuring the width of the valley-bottom zone) requires Coordinate Geometry (COGO) in the ARCEDIT module. The process requires three inputs: a polygon coverage of the analysis area; an arc coverage of its hydrography, and a grid representing its digital elevation. The AML is designed to operate within a wide range of computer memory/disk space options, and it allows users to customize several procedures to match the scale and complexity of a given analysis area with available computer hardware.     

Sink–float density separation of post-consumer plastics for feedstock recycling

The paper focuses on current mechanical waste processing technologies and out-of-the-box processes linked to the processing of coal and mineral resources, to ensure high-quality feedstock recycling of polyolefin-rich post-consumer plastic fractions. Moreover, the study aims to provide the basis for the technical and economic feasibility of the chemical recycling route of this plastic fraction. When evaluating common mechanical processes, either dry or wet ones, sink–float separation in a cylindrical centrifugal force separator achieves the best results. It combines the advantages of a simple, robust apparatus of low complexity and high capacity with selective separation through the accelerated settling of particles in the centrifugal field. Furthermore, the disconnection of the separation medium feed from the solid input increases residence times. Based on the above findings, a pilot-scale plant was constructed which consists of a centrifugal force separator and a hydro jig for the pre-separation of heavy waste components. Several test campaigns were conducted to separate polyolefins from various waste fractions. Two-stage processing in the centrifugal force separator rendered almost 90 wt% of polyolefin content in the produced lightweight fraction and of polyolefin recovery. One-stage processing, on the other hand, resulted in reduced polyolefin content in the lightweight fraction.

     

Percolation of clay liners of ash landfills in short and long time perspectives.

Top covers of waste landfills conventionally contain a drain layer over a 1(low-permeable clay liner usually containing smectite minerals. The rate of percolation of the clay liner, which may require tens of years to become water-saturated, determines the downward transport of ions released from the underlying waste to and through the bottom clay liner. The percolation rate is controlled by the composition and density of the tipper liner, which should be as tight as possible. This implies a high density and therefore a high swelling potential which must be moderated by proper design. The bottom clay liner is a less effective and reliable barrier since cation exchange will increase the hydraulic conductivity and cause a significant rise in percolation rate and risk of chemical attack by the percolate. The top liner will undergo very moderate strain if the ash fill is effectively compacted and undergoes little self-compaction. Processes that may cause degradation are freezing and drying and require proper design. In this paper the authors examine the performance of ash-fills isolated by clay liners and conclude that the most important issue is to design and construct the top liner to be as impermeable as possible paying less attention to the tightness of the bottom layer.     

Untersuchungen zur Charakterisierung von Brandrauch

The aim of this work is to clarify if there is a correlation between fuel and its organic combustion products. To acquire homogenous data sets for our investigations, we analysed only the measurements of the “Forschungsstelle für Brandschutztechnik” at the University of Karlsruhe. All compounds with a similar structure were grouped and structural indices were ascribed to them. This also made it possible to obtain information about the frequency of occurrence of a set of substances in fire smoke. The kind of analytical measurements used by this institute provided no or only little information about inorganic compounds, highly volatile substances like acrolein or vinyl chloride, and very poorly volatile substances (e.g. polycyclic aromatic hydrocarbons). We found that benzene, methylbenzene, ethenylbenzene and ethylbenzene are always present in fire smoke. The formation of these typical compounds is described by a model. Aside from these compounds which are typically related to the smoke from fires, substances are always observed which are typical for a distinct fuel. Many compounds which are expected to be in the smoke are highly carcinogenic. Therefore, it is necessary for people with a high exposure to the smoke of fires, e.g. firemen, to protect themselves efficiently. In order to obtain more information about the risks to health of fire smoke, toxicological investigations will be necessary.     

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