Modelling changes in nitrogen emissions into the Oder River System 1875–1944

Studies of nutrient emissions into surface waters are usually only performed for years in recent decades. However, estimating nutrient emissions for the more distant past enables us to identify the main factors responsible for the increasing nutrient contamination since the end of the nineteenth century. We focussed on the Oder River System for 1875–1944, divided into 10-year periods. Nutrient emissions into surface waters were calculated with the model MONERIS (MOdelling Nutrient Emissions in RIver Systems). For seven different pathways and eight sources, the total nitrogen (TN) emissions were quantified. The TN-emissions into the surface waters for 1880 amounted to 25,300 t?year^?1, and by 1940, this value had almost doubled to 46,600?t?year^?1. In 1880, 57% of TN-emissions into the surface waters derived from urban systems, due to the high amount of untreated waste water. In 1940, only 34% of TN-emissions into surface waters derived from urban systems, despite a population growth of about 27% since 1880; point sources via newly constructed waste water treatment plants (WWTPs) increased from 4% (1880) to 26% (1940). During the study period, the main changes in diffuse TN-emissions from agriculture were caused by inorganic fertilizer application and nitrogen deposition, while TN-emissions via urban sources were shifted to point sources due to population growth and the construction of new WWTPs. Furthermore, estimated TN-concentrations could make a contribution to construct benchmarks for nutrient concentrations according to the physiochemical properties to implement the European Water Framework Directive (WFD 2000).     

Laboratory studies on formation and minimisation of polychlorinated dibenzodioxins and -furans (PCDD/F) in secondary aluminium process

The objectives of this work were to study the formation mechanisms of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/F) in thermal aluminium recycling processes by use of laboratory experiments. The pattern of isomers of PCDD/F indicates that de novo synthesis is important in aluminium smeltery. The mechanisms of PCDD/F formation in aluminium smelting are similar to that of various incineration processes of waste material. The results of bioanalysis (EROD-test) confirms the existence of de novo synthesis of PCDD/F, but points out to the existence to some additional, toxic compounds of unknown structure. To reduce the amount of PCDD/F the input of carbon at the metal should be reduced; in addition the metal smeltery plants should be cleaned from fly ash particles. It is suggested to use good primary methods in the technical plants like constant feeding of the metal into the oven will minimise PCDD/F concentration. The biological EROD-bioassay is a good tool to estimate PCDD/F-TEQ values also for this technical process simulated in the laboratory.     

Enzymatic synthesis of bromo- and chlorocarbazoles and elucidation of their structures by molecular modeling

3-Chlorocarbazole, 3,6-dichlorocarbazole, dibromocarbazole, and 1,3,6,8-tetrabromocarbazole are emerging environmental contaminants which have been detected recently in water, sediment, and soil samples. However, their sources and occurrence have not been explained. Here, we report an enzymatic synthesis of bromo- and chlorocarbazoles by chloroperoxidase from Caldariomyces fumago in water. Density functional theory (DFT) method was used to predict the most stable products. Carbazole and chloroperoxidase were assayed in vitro in the presence of hydrogen peroxide, bromide, and chloride ions in different substrate ratio treatments against constant and varying enzyme concentrations. Halogenated carbazoles formed were identified by high-resolution gas chromatography coupled to mass spectrometry. In all treatments, bromination and chlorination took place, but the composition and concentration of compounds formed varied from one treatment to another. Mono-, di-, tri-, and tetra-substituted bromo- and chlorocarbazoles which include the reported environmental contaminants were synthesized. 3-Substituted and 3,6-substituted congeners were relatively higher in concentration. Enzyme concentration did not favor preferential formation of any of the compounds synthesized. However, their synthesis was influenced by halide concentration. Congeners with bromine and chlorine at position of C-3, C-3,6, C-1,3,6, and C-1,3,6,8 were calculated as the stable intermediate sigma complexes by DFT method. Regioselectivity in halogenation is discussed and hypothesis of the likely stable products in the environment explained. This study provides evidence that bromo- and chlorocarbazoles reported previously can be formed enzymatically in the environment, demonstrating the need to consider aromatic pollutants transformation and their potential toxicity enhancements in the management of water pollution and contaminated sites.     

Benzoic acid, a stimulant of odorant receptors of Bombyx mori, is rapidly metabolized to N-benzoylserine on the antennae

Summary. Benzoic acid is a known stimulant of olfactory receptor cells in trichoid sensilla on the antennae of adult females of Bombyx mori. Exposure of freshly excised antennae, from B. mori females and males, to vapours of [¹⁴C]-benzoic acid revealed that the adsorbed acid is rapidly metabolized (15% conversion in 10 s), suggesting the presence of a highly active enzymatic system. The major product could be identified as N-benzoylserine by use of [²H₅]-benzoic acid, and mass spectrometry linked to a gas chromatograph (GC-MS) or a liquid chromatograph (LC-MS), for analysis of the metabolites. The conjugation of benzoic acid with an amino acid apparently represents a novel mode for the rapid deactivation of odorant molecules. Received 26 March 2001.     

MR imaging of the fetal musculoskeletal system

Magnetic resonance imaging (MRI) appears to be increasingly used, in addition to standard ultrasonography for the diagnosis of abnormalities in utero. Previous studies have recently drawn attention to the technical refinement of MRI to visualize the fetal bones and muscles. Beyond commonly used T2-weighted MRI, echoplanar, thick-slab T2-weighted and dynamic sequences, and three-dimensional MRI techniques, are about to provide new imaging insights into the normal and the pathological musculoskeletal system of the fetus. This review emphasizes the potential significance of MRI in the visualization of the fetal musculoskeletal system. © 2012 John Wiley & Sons, Ltd.