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Lev Kh. Ingel 《Environmental Fluid Mechanics》2006,6(4):303-311
The paper considers the problem concerning the response of a stably stratified two-component medium (salt water, moist air)
in the presence of a stationary source of vertical impulse. For a homogeneous vertical distribution of the impulse source
(i.e., the applied vertical force), due to the symmetry of the problem, one succeeded in finding the explicit analytical solution
of the stationary problem for arbitrary source amplitude. The solution is expressed through Kelvin’s cylindrical functions
and represents the stationary vertical jet. The two-component character of the medium can influence substantially the quality
of the properties of the solution. In particular, the jet parameters are not defined uniquely by the buoyancy frequency (density
stratification). In the solution, the stratifications of the two hydrodynamic components have the distinctive influences that
are defined by values of corresponding exchange coefficients. For example, in salt water the solution dependence on salinity
stratification may be much more than on temperature stratification. 相似文献
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A Multispecies Approach to Ecological Valuation and Conservation 总被引:3,自引:0,他引:3
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Pilot study of sources of lead exposure in Moscow,Russia 总被引:11,自引:0,他引:11
Anna O. Orlova Desmond I. Bannon Mark R. Farfel Valerie M. Thomas Lev V. Aleschukin Valery V. Kudashov James P. Shines Georgy I. Kruchkov 《Environmental geochemistry and health》1995,17(4):200-210
This preliminary investigation of sources of lead exposure in Moscow, Russia, by Russian and US collaborators measured lead in paint, interior dust, and drinking water in seven day-care centres, and in petrol, soil and canned food. Some paint samples exceeded US regulatory standards for lead in paint on surfaces (0.5%). Dust lead loadings were < 1.7 g cm–2 and below the guidance levels of the US EPA. Drinking water lead concentrations were at or below the US drinking water standard of 15 g L–1. Lead concentrations in petrol from Moscow vehicles and petrol stations were consistent with a regulation banning the sale of leaded petrol within the Moscow City limits. Except for baby food, lead levels were higher in the Russian canned foods (range 6 to 1240 g kg–1, dry weight) compared to corresponding US canned foods, with ratios of Russian to US levels of up to 120:1 for evaporated milk. Lead concentrations in soil generally ranged from 500 to 2000 g g–1, levels that would trigger hazard reduction measures according to US EPA guidance. These findings, together with the use of lead in petrol outside Moscow, indicate multiple sources of lead exposure in Russia. Priorities for future research are discussed including the establishment of interlaboratory quality control programmes. 相似文献
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Soil microbial diversity and C turnover modified by tillage and cropping in Laos tropical grassland 总被引:3,自引:0,他引:3
Pascal Lienhard Sébastien Terrat Olivier Mathieu Jean Levêque Nicolas Chemidlin Prévost-Bouré Virginie Nowak Tiffanie Régnier Céline Faivre Sengphanh Sayphoummie Khamkéo Panyasiri Florent Tivet Lionel Ranjard Pierre-Alain Maron 《Environmental Chemistry Letters》2013,11(4):391-398
Agricultural practices should modify the diversity of soil microbes. However, the precise relationships between soil properties and microbial diversity are poorly known. Here, we study the effect of agricultural management on soil microbial diversity and C turnover in tropical grassland of north-eastern Laos. Three years after native grassland conversion into agricultural land, we compared soils from five land use management systems: one till versus two no-till rotational cropping systems, one no-till improved pasture and the natural grassland. Soils were incubated in microcosms during 64 days at optimum temperature and humidity. Bacterial and fungal diversity were evaluated by metagenomic 454-pyrosequencing of 16S and 18SrRNA genes, respectively. Changes in soil respiration patterns were evaluated by monitoring 12C- and 13C-CO2 release after soil amendment with 13C-labelled wheat residues. Results show that residue mineralization increased with bacterial richness and diversity in the tilled treatment 7 days after soil amendment. Native soil organic C mineralization and priming effect increased with fungal richness and diversity in improved pasture and natural grassland. No-till cropping systems represented intermediate situations between tillage and pasture systems. Our findings evidence the potential of controlling soil microbial diversity by agricultural practices to improve soil biological properties. We suggest the promotion of no-till systems as a fair compromise between the need for agriculture intensification and soil ecological processes preservation. 相似文献
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The stereoselectivity of R,S-venlafaxine and its metabolites R,S-O-desmethylvenlafaxine, N-desmethylvenlafaxine, O,N-didesmethylvenlafaxine, N,N-didesmethylvenlafaxine and tridesmethylvenlafaxine was studied in three processes: (i) anaerobic and aerobic laboratory scale tests; (ii) six wastewater treatment plants (WWTPs) operating under different conditions; and (iii) a variety of wastewater treatments including conventional activated sludge, natural attenuation along a receiving river stream and storage in operational and seasonal reservoirs. In the laboratory and field studies, the degradation of the venlafaxine yielded O-desmethylvenalfaxine as the dominant metabolite under aerobic and anaerobic conditions. Venlafaxine was almost exclusively converted to O-desmethylvenlafaxine under anaerobic conditions, but only a fraction of the drug was transformed to O-desmethylvenlafaxine under aerobic conditions. Degradation of venlafaxine involved only small stereoisomeric selectivity. In contrast, the degradation of O-desmethylvenlafaxine yielded remarkable S to R enrichment under aerobic conditions but none under anaerobic conditions. Determination of venlafaxine and its metabolites in the WWTPs agreed well with the stereoselectivity observed in the laboratory studies. Our results suggest that the levels of the drug and its metabolites and the stereoisomeric enrichment of the metabolite and its parent drug can be used for source tracking and for discrimination between domestic and nondomestic wastewater pollution. This was indeed demonstrated in the investigations carried out at the Jerusalem WWTP. 相似文献
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