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991.
M. T. Moore D. B. Huggett G. M. Huddleston III J. H. Rodgers Jr. C. M. Cooper 《Chemosphere》1999,38(15):1709-3647
Aqueous 7-d germination and growth experiments were performed to compare responses of T. latifolia to exposures of atrazine (2-chloro-4-ethylamino-6-isopropylamine-s-atrazine) and paraquat dichloride (1,1′-dimethyl-4,4′-bipyridinium dichloride). T. latifolia seed germination was < 50 % in concentrations ≥ 1.0 mg/L of paraquat dichloride. No observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for paraquat and root growth were 0.001 and 0.01 mg/L, respectively, while NOEC and LOEC for paraquat and shoot growth were 0.01 and 0.1 mg/L, respectively following 7-d exposures. Greater than 72 % of seeds germinated in each concentration up to 30 mg/L atrazine. After 7-d exposure, NOEC and LOEC for atrazine and root growth were 0.1 and 1.0 mg/L, while atrazine and shoot growth NOEC and LOEC values were 15 and 30 mg/L, respectively. This research provides data concerning relative sensitivity of T. latifolia seedlings to the herbicides atrazine and paraquat, as well as the potential use of T. latifolia as a representative plant test species. 相似文献
992.
A procedure for the determination of 13 organophosphate insecticides (OPs) in water, sediment and biota at low ppb levels is described. Samples were extracted with dichloromethane or acetone/hexane and cleaned up with micro-column silica gel chromatography. Measurements were made by dual capillary column gas chromatography using both nitrogen-phosphorus (NPD) and electron capture (ECD) detection. Recoveries from fortified water samples ranged from 76% to 102% for all sample types. Practical detection limits ranged between 0.003 and 0.029 microg/l in natural water samples, 0.0004-0.005 microg/g w.w. for sediments, and 0.001-0.005 microg/g w.w for biota using the NPD and ECD method. Losses in sediments were experienced when sulphur was removed. Precision and accuracy were not affected in sediment samples where sulphur was not removed. 相似文献
993.
Weisbrod N Niemet MR Rockhold ML McGinnis T Selker JS 《Journal of contaminant hydrology》2004,72(1-4):109-133
Migration of concentrated NaNO3 solutions in homogeneous packs of pre-wetted silica sands was investigated using a light transmission system. Solutions of 5 molal NaNO3 were found to migrate downward 24-62% faster than pure water, in an unstable, fingered manner. This behavior was attributed primarily to a surface tension induced, non-zero apparent contact angle between the imbibing and the resident fluids. For saline solutions of similar surface tension to that of pure water (achieved by the addition of 2% methanol), the migration rates and plume shapes were comparable to that of water, demonstrating that density was not the primary source of the observed differences in migration patterns. At depths where resident saturation increased above residual, the migration process appeared to occur via film flow with slight changes in saturation (<4%), rather than in a series of abrupt jumps, as observed at shallower depths. A method for contact angle scaling was used to illustrate the effects of non-zero contact angles on capillary pressure-saturation curves. 相似文献
994.
Porewater chemistry in compacted re-saturated MX-80 bentonite 总被引:2,自引:0,他引:2
Bentonites of various types are being investigated in many countries as backfill materials in high-level radioactive waste disposal concepts. Being able to understand the chemistry of the porewater in compacted bentonite is very important since it is critical to predicting radionuclide solubilities and to the synthesis of sorption data bases, and hence to repository safety studies. In this paper, porewater compositions in compacted bentonites are calculated, taking into consideration such factors as montmorillonite swelling, semi-permeable membrane effects, very low "free water" volumes, and the highly effective buffering characteristics of the exchangeable cations and the amphoteric edge sites. The former buffer the cation concentrations and the latter fix the pH in the porewater of a re-saturated bentonite. The above considerations are used in conjunction with previously measured physico-chemical characterisation data on MX-80 powder to calculate porewater compositions in compacted bentonites. For the MX-80 material specified, the porewaters calculated for initial dry densities between 1200 and 1600 kg m(-3) had relatively high ionic strengths (I approximately 0.3 M), similar cation concentrations and a pH equal to 8.0. The porewaters changed from being Na(2)SO(4)-rich at 1200 kg m(-3) to a NaCl/Na(2)SO(4) type water at 1600 kg m(-3). 相似文献
995.
Derwent RG Stevenson DS Doherty RM Collins WJ Sanderson MG Johnson CE Cofala J Mechler R Amann M Dentener FJ 《Ambio》2005,34(1):54-59
A global three-dimensional Lagrangian chemistry-transport model STOCHEM is used to describe the European regional acid deposition and ozone air quality impacts along the Atlantic Ocean seaboard of Europe, from the SO2, NOx, VOCs and CO emissions from international shipping under conditions appropriate to the year 2000. Model-derived total sulfur deposition from international shipping reaches over 200 mg S m(-2) yr(-1) over the southwestern approaches to the British Isles and Brittany. The contribution from international shipping to surface ozone concentrations during the summertime, peaks at about 6 ppb over Ireland, Brittany and Portugal. Shipping emissions act as an external influence on acid deposition and ozone air quality within Europe and may require control actions in the future if strict deposition and air quality targets are to be met. 相似文献
996.
Four phosphorus forms were investigated as potential soil amendments to decrease the bioavailability of Pb and Zn in two repository soils to the earthworm, Eisenia fetida. Treatments were evaluated by examining differences in bioaccumulation factors between amended and non-amended soils. Triple super phosphate at 5000 mg P/kg decreased both Pb and Zn bioavailability in both soils. Rock phosphate at 5000 mg P/kg decreased Zn bioavailability, but not Pb bioavailability in both repository soils. Monocalcium phosphate and tricalcium phosphate at 5000 mg P/kg did not significantly decrease Pb or Zn bioavailability to earthworms in either repository soil. In order to optimize phosphorus amendments, additional phosphorus (up to 15,000 mg P/kg) and lowered pH were used in a series of tests. The combination of lowering the pH below 6.0 and increasing phosphorus concentrations caused complete mortality in all triple super phosphate amended soils and partial mortality in the highest rock phosphate amended soils. Results indicate that triple super phosphate and rock phosphate are viable soil amendments, but care should be taken when optimizing amendment quantity and pH so that adverse environmental effects are not a by-product. 相似文献
997.
Jürgen Burhenne Marc Ludwig Michael Spiteller 《Environmental science and pollution research international》1997,4(2):61-67
Subsequent to irradiation with a xenon lamp simulating sunlight, fluoroquinolone carboxylic acids in aqueous solution form
polar pyridone dicarboxylic and tricarboxylic acids. After liquid/liquid partition with chloroform/water these substances
can be isolated by ion exchange chromatography of the aqueous phase. They can be regarded as intermediate compounds on the
route to a complete photomineralization. The structural elucidation is performed by such mass spectroscopic methods as MS,
GC/MS and HPLC/MS, whereby HPLC/MS shows the highest reliability. Additionally1H- and13C-NMR measurements confirm the structure of the main polar degradation product. 相似文献
998.
Die Modellierung des Ausbreitungsverhaltens von Stoffen unterschiedlicher Eigenschaften in der Umwelt stellt eine Herausforderung
dar, da die zugrundeliegenden physikalischen Transport-, chemischen Reaktions- und biologischen An- oder Abreicherungsprozesse
zeitlich variabel in r?umlich heterogen strukturierten Umweltsystemen wirken. Durch geschickt gew?hlte Vereinfachungen, Abgrenzungen
und Mittelungen sind bemerkenswerte Erfolge bis hin zur bedingt-prognostischen Simulation ausgew?hlter Stoffe und Stoffgruppen
erzielt worden. Forschungsbedarf besteht vor allem in der Modellierung der kleinr?umigen, medienübergreifenden Ausbreitung
von Stoffen in komplexen ?kosystemaren Zusammenh?ngen, einschlie?lich der Austausch- und Transfervorg?nge und der chemisch-biologischen
Transformationen.
Bericht vom 32. Tutzing-Symposium der DECHEMA e.V., 7. bis 10. M?rz 1994 相似文献
999.
Farming Endangered Turtles to Extinction in China 总被引:1,自引:0,他引:1
1000.
Pat M. Fidopiastis Daniel J. Bezdek Michael H. Horn Judith S. Kandel 《Marine Biology》2006,148(3):631-642
The zebraperch, Hermosilla azurea Jenkins and Evermann, a warm-temperate marine fish species with a strictly macroalgal diet, has a relatively long digestive
tract with an enlarged hindgut and an associated blind caecum (HC). In zebraperch sampled off Santa Catalina Island, California
(33°19′42′′N; 118°18′37′′W) in years 1995 through 2001, direct cell counts, gut epithelium assessment of bacterial attachment,
and short-chain fatty acid (SCFA) analyses verified that the zebraperch HC possesses a dense and morphologically diverse,
fermentative microbiota. Bacterial cell counts and morphological diversity were significantly higher in HC contents compared
to anterior gut regions, suggesting that microbial populations were growing along the digestive tract. Similarly, electron
micrographs of the HC epithelium revealed attached microbes, further supporting the possibility that these organisms constitute
resident microbiota. Five different SCFAs were detected in all three regions of the digestive tract, but levels were up to
three times greater in HC contents. Acetate was consistently the prevailing SCFA in all gut regions. Sequence analysis of
bacterial 16S rDNA was used to identify predominant bacterial groups in HC contents. Of the seven main bacterial types identified,
Enterovibrio spp. were the dominant bacteria in HC contents followed by species of Bacteroides,Faecalibacterium, and Desulfovibrio. Taken together, our findings show that the zebraperch HC harbors a consortium of microbes that appears to assist in the
breakdown of algal polysaccharides in the herbivorous diet of the fish. 相似文献