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91.
Chronic effects of ozone on wet grassland species early in the growing season might be altered by interspecific competition. Individual plants of Holcus lanatus, Lychnis flos-cuculi, Molinia caerulea and Plantago lanceolata were grown in monocultures and in mixed cultures with Agrostis capillaris. Mesocosms were exposed to charcoal-filtered air plus 25 nl l(-1) ozone (CF+25), non-filtered air (NF), non-filtered air plus 25 nl l(-1) ozone (NF+25) and non-filtered air plus 50 nl l(-1) ozone (NF+50) early in the growing seasons of 2000 through 2002. Ozone-enhanced senescence and visible foliar injury were recorded on some of the target plants in the first year only. Ozone effects on biomass production were minimal and plant response to ozone did not differ between monocultures and mixed cultures. After three years, above-ground biomass of the plants in mixed culture compared to monocultures was three times greater for H. lanatus and two to four times smaller for the other species.  相似文献   
92.
In rats, dibenzo-p-dioxin, 1-chlorodibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin, 2,3-dichlorodibenzo-p-dioxin, 2,7-dichlorodibenzo-p-dioxin, 1,2,4-trichlorodibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin are metabolized to mono- and dihydroxy derivatives, whilst in case of dibenzo-p-dioxin and both the two monochloro isomers, also sulphur containing metabolites are excreted. Primary hydroxylation exclusively takes place at the 2-, 3-, 7- or 8-position in the molecule. In none of the experiments metabolites resulting from fission of the C-O bonds (ortho, ortho'-dihydroxychlorodiphenyl ethers, chlorocatechols) or hydroxylated derivatives thereof, were detected. No metabolites were found from octachlorodibenzo-p-dioxin.  相似文献   
93.
The phenylurea herbicide metoxuron and its main metabolite, 3-chloro-4-methoxyaniline, can be determined rapidly in aqueous samples via extraction, derivatization with heptafluorobutyric anhydride (HFBA), washing with an aqueous bufferof pH 8, and analysis by capillary GC with electron capture detection. Linear calibration curves are obtained over two orders of magnitude, and the detection limit for the HFB derivatives is about 0.5 pg. The method has successfully been applied to several types of water samples.  相似文献   
94.
W?hrend eines Studien- und Beratungs-aufenthalts des Autors bei der Saudi-Arabischen Umweltbeh?rde im Juni/Juli 1991 wurde der Zustand der Saudi-Arabischen Golfküste untersucht. Von der Kuwaitischen Grenze bis zur Insel Abu Ali sind ca. 770 km Küste lückenlos zwischen Hoch- und Niedrigwasserlinie ver?lt. W?hrend an den energiereicheren Au?enküsten eine biologische Regeneration erwartet werden kann, ist sie in den energiearmen Buchten nicht ohne technische Ma?nahmen denkbar. Ver?lungen gibt es au?erdem am Meeresgrund in noch unbekanntem Ausma?. Für die Ma?nahmen wird die Notwendigkeit betont, ein Umweltqualit?tsziel festzulegen, das in der Entwicklung zu einem Naturreservat bestehen sollte.  相似文献   
95.
The metabolism of 2,5-dichloro-4'-isopropylbiphenyl and 4-chloro-4'-isopropylbiphenyl, two model compounds for alkylated chlorobiphenyls (Chloroalkylenes), has been investigated in fish, frogs, fungi and mixed cultures of bacteria. Fish (Carassius auratus) and frogs (Rana aesculenta) show a very limited metabolism of these compounds. A pure strain of fungus (Cunninghamella echinulata Thaxter) metabolized 2,5-dichloro-4'-isopropylbiphenyl both by stepwise oxidation of the isopropyl group to 2,5-dichloro-4'-biphenylcarboxylic acid and by hydroxylation of the chlorine substituted phenyl ring. A mixed culture of aerobic bacteria from activated sludge shows extensive degradation of 4-chloro-4'-isopropylbiphenyl to p-chlorobenzoic acid via stepwise oxidation of the isopropyl group when using the compound as sole carbon source. However, in the presence of D-glucose as additional carbon source, no metabolism is observed.  相似文献   
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98.
In order to evaluate the performance of different methods for estimation of the vertical eddy diffusivity in thermally stratified lakes, two field studies were conducted in Lake Biwa, Japan and Lake Kinneret, Israel. Lake Biwa experienced three typhoons during the campaign while Lake Kinneret experienced high winds in the afternoons. Microstructure profiles were collected by a portable flux profiler (PFP) during calm and disturbed periods. Then, the vertical eddy diffusivity was estimated by three indirect methods. The estimated vertical eddy diffusivities varied more than one order of magnitude, from 4.7× 10−7 to 7.7× 10−6 m2 s−1. The comparison of results with previous buoyancy flux measurements and scaling arguments showed that the Dillon–Park’s method is not appropriate and Osborn–Cox method performs better than Osborn method in the studied case. Furthermore, the low value of vertical eddy diffusivity within the thermocline suggests that within the thermocline of these lakes, diffusive vertical transport can be neglected.  相似文献   
99.
The endotoxic principle of lipopolysaccharides (LPS) is localized in their lipid A component. Biological effects of LPS on, for instance, body temperature, blood pressure, and blood picture, are also induced by free lipid A. In contrast to the great variability of the 0-specific chains, the chemical structure of lipid A is much more constant. It is common for Salmonella and similar for other genera of the Enterobacteriaceae. Recently, a number of lipid A's have been recognized that exhibited distinct structural features compared with Enterobacteriaceae. These lipid A's were found to be also distinct with regard to some of their biological properties.  相似文献   
100.
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