خيارات البحث
النتائج 1 - 10 من 174
Determination of organohalogenated contaminants in liver of harbour porpoises (Phocoena phocoena) stranded on the Belgian North Sea coast
2002
Covaci, Adrian | Van de Vijver, Kristin Inneke | De Coen, Wim | Das, Krishna | Bouquegneau, Jean-Marie | Blust, Ronny | Schepens, Paul | MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
peer reviewed
اظهر المزيد [+] اقل [-]Design criteria and performances of reed bed filters for the treatment of washing parlour effluents
2002
Lienard, A. | Esser, D. | Houdoy, D. | Sabalcagaray, P.
Conçus initialement pour le traitement des eaux usées domestiques, les filtres plantés de roseaux ont été adaptés pour le traitement des effluents de lavage de salles de traite pour fournir une alternative au stockage et épandage. Pour simplifier les système en vue de réduire les coûts d'investissement, plusieurs sites expérimentaux ont été construits, modifiés si nécessaire et suivis. Placé à la suite d'une fosse toutes eaux de 3 à 9 m3, la configuration la plus aboutie consiste en 2 étages des filtres plantés à flux verticaux chacun étant composé de 2 filtres alimentés en alternance chaque semaine. La surface totale active correspond à 0.25m2 par vache laitière pour les eaux blanches seules (machine à traire et tank à lait) et 0.4m2 par vache lorsque s'y ajoutent les eaux vertes de lavage des quais et murs de la salle de traite. Les filtres du 1er étage occupent 65% de la surface totale. Observées dans 3 exploitations agricoles laitières, les concentrations obtenues atteignent une fourchette de 50 à 180 mg/L en DCO, 5 à 75 mg/L en DBO5 et 10 à 60 mg/L en MES. La nitrification qui est considérée comme un bon indicateur du potentiel d'oxydo-réduction dans le réacteur n'est certes pas complète mais beaucoup plus élevée que dans le cas de filtres à sable étudiés pour le même objectif alors que plusieurs d'entre eux ont colmaté. / Initially designed for the treatment of domestic wastewater, Vertical Flow Reed Bed Filters [VFRBF] have been adapted for washing parlour effluents to study the feasibility of the treatment of such effluents instead of their storage and land spreading. It was necessary to adapt the design of VFRBF to minimise the investment costs. Several experimental sites have been built, monitored and progressively adapted. Following a septic tank of 3 to 9 m3, the best design was considered to be: 2 stages of VFRBF in series each composed of 2 filters which are alternately fed on a weekly rhythm. The total active area is approximately equivalent to 0.25 m2 per milking cow for the washing effluent of the milking machine and milk-storage tank and 0.4 m2 per milking cow when the washing effluents from the floor and walls of the milking parlour are added to the previous ones. The 1st stage filters takes up 65 % of the total area. Based on a survey done in 3 farms, the concentrations achieved a range of 50 to 180 mgL-1 in COD, 5 to 75 mgL-1 in BOD5, 10 to 60 mgL-1 in SS. The nitrification, which can be considered as a good indicator of the redox potential within the filter media, was not complete but much more effective than in sand filters studied for the same purpose but some of them have clogged.
اظهر المزيد [+] اقل [-]Phosphorus sorption in subsurface constructed wetlands: investigations focused on calcareous materials and their chemical reactions
2002
Molle, Pascal | Lienard, A. | Grasmick, A. | Iwema, A.
Phosphorus removal from wastewater has been of growing interest for some decades to avoid eutrophication in surface water. In subsurface constructed wetlands precipitation and adsorption are the main mechanisms responsible of P uptake. The use of calcareous media is attractive because of p-ca interactions. Two media (calcite and recycled crushed concrete (rcc)) were examined in batch and continuous systems. They show attractive sorption capacities using batch experiments, however experiments carried out in open reactors pointed out some limitation in retention capacities and effluent quality. rcc was sensitive to a strong dissolution leading to a quick phosphorus precipitation but induced high conductivity and ph values in the treated water. Calcite efficiency depended on the material dissolution rate, directly linked to the carbonate equilibrium of the solution. Microscopic observations of the calcite surface show crystal making of phosphorus precipitate. Crystal growth seems to be the main P uptake once materials surfaces are covered. No experimental condition allows to reach an effluent concentration below 2 mgp.l-1.
اظهر المزيد [+] اقل [-]The measurement of cholinesterase activities as a biomarker in chub (Leuciscus cephalus): the fish length should not be ignored | Les mesures de l'activité de la cholinesterase utilisé comme biomarqueur pour les chevaines (Leuciscus cephalus) : doit-on tenir compte de la taille du poisson ?
2002
Flammarion, Patrick | Noury, P. | Garric, Jeanne | Biologie des écosystèmes aquatiques (UR BELY) ; Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF)
[Departement_IRSTEA]GMA [TR1_IRSTEA]12 - MILEAU / EXPER | International audience | Biomarkers are early warning systems of the exposure of aquatic organisms to pollutants. Among them, the measurement of the cholinesterase (ChE) activities in fish muscle is a biomarker of the exposure to organophosphosphates and carbamates pesticides. As Such it has been used in numerous field studies both in marine and continental waters. Cyprinids (chub, Leuciscus cephalus) were sampled in river sites (France) in relatively clean and polluted areas. We performed the statistical analysis of the ChE activities and we generally observed a statistical relationship between ChE activities and fish length, the larger fish having the lower ChE activities. We concluded that the great majority of the significant differences in ChE activities between sites could be due in fact to differences in fish length between field samples. We stress the importance of taking into account the fish length whenever differences in ChE levels between field sites must be interpreted.
اظهر المزيد [+] اقل [-]Assessment of exceedance of critical levels for ozone in Slovak forest ecosystems
2002
Pavlendova, H. | Mindas, J. (Forest Research Institute, Zvolen (Slovak Republic))
For assessment of ozone risks to forests we used ozone thresholds and air quality guidelines set by several international organizations for protection of vegetation. We also used spatial modelling for estimation of basic ozone characteristics. Calculations of models were performed in the environment of the programme Idrisi 32. The spatial coverage of ozone monitoring network in the Slovak Republic has insufficient density. Ozone data come from two sources; SHMI/EMEP database of ozone concentrations from 4 monitoring stations and ozone database of FRI from 3 monitoring stations
اظهر المزيد [+] اقل [-]Effect of increased carbon dioxide and ozone on leaf spot pathogens of birch
2002
Syrjala, L. | Poteri, M. (Finnish Forest Research Institute, Suonenjoki (Finland). Suonenjoki Research Station)
Both CO2 and ozone increased the diseased leaf area of clone V5952 in Exp. 1 in the year 2000. The size of spots increased most under ozone fumigation, and the number of spots under ozone and CO2 + O3 fumigations. In clone K1659 all fumigation treatments decreased or had no effect on the DLA, or the number and size of the leaf spots. Also the number of fallen leaves under fumigation treatments was higher in clone V5952 than in clone K1659. Analysis of the year 2001 monitoring results is currently going on
اظهر المزيد [+] اقل [-]Fine root status and element contents in three stands of Norway spruce in the Krkonose mountains
2002
Godbold, D.L. (University of Wales, Bangor (United Kingdom). School of Agricultural and Forest Sciences) | Fritz, H.W. | Cudlin, P. | Bonifacio, E.
Fine root distribution was estimated in three spruce stands with different stages of forest decline. At all 3 sites in the 0-5 cm layer the density of living fine root mass exceeds the necromass. However, in the deeper soil layer necromass exceeds biomass by a factor of 2-4 at Modry Dul, ca. 3 at Alzbetinka and by more than 8 at Mumlavska Hora. The distribution of root density was reflected in the distribution of root length and the number of root tips in each soil layer for the 3 sites
اظهر المزيد [+] اقل [-]Depositions from precipitation in the forest ecosystem of pedunculate oak and their possible impacts on the stability of the lowland forests in Croatia
2002
Tikvic, I. (University of Zagreb, Zagreb (Croatia). Faculty of Forestry) | Seletkovic, Z. | Sojat, V. | Znidaric, G.
The paper deals with the results of chemical analyses of the precipitation collected with the bulk method in and out of the pedunculate oak forest near Lipovljani in Croatia, for the period 1997-2001. A considerable higher total annual deposition of the majority of analysed determinants has been found in the forest. The results point to the importance and influence of the forest cover on the reception and distribution of dry and wet pollution in the forest ecosystem of pedunculate oak
اظهر المزيد [+] اقل [-]Effects of elevated CO2 and O3 on stem wood chemistry in trembling aspen, paper birch and sugar maple
2002
Anttonen, S. (Finnish Forest Research Institute, Suonenjoki (Finland). Suonenjoki Research Station) | Kostianen, K. | Vapaavuori, E. | Isebrands, J. G. | McDonald, E. | Sober, J. | Karnosky, D. F.
Global environmental change, including increasing atmospheric CO2 and tropospheric O3 is likely to impact forest growth and wood properties. Increase in CO2 enhances photosynthesis, growth and productivity. On the contrary, O3 is detrimental to forest vitality and yield. At present reports of long-term studies on the effects of combined exposures of CO2 and O3 on stem wood chemistry of deciduous trees are lacking. The aim of this study was to investigate the effects of CO2 and O3, singly or in combination, on stem wood chemistry of four-year old saplings of trembling asspen (Populus tremuloides) clones differing in ozone tolerance, paper birch (Betula papyrifera) and sugar maple (Acer saccharum)
اظهر المزيد [+] اقل [-]Soil nutrients in a mature natural mixed forest exposed to elevated CO2
2002
Bucher-Wallin, I. K. | Schleppi, P. | Hagedorn, F. | Bucher, J. B. (Swiss Federal Research Institute WSL, Birmensdorf (Switzerland))
Elevated CO2 was shown to influence the nutritional status of exposed ecosystems. In an earlier experiment in model ecosystems in open-top chambers with young spruce and beech, the nitrate concentration of the soil solution was dramatically reduced after 4 years exposure to elevated CO2. This phenomenon was mainly interpreted as an immobilization of nitrogen in the soil. To test if such effects occur also in mature, undisturbed natural forests, we used facilities of the Swiss Canopy Crane project. Here in a mixed 120 years old forest the crowns of 30-35 m high broadleaved trees are fumigated with CO2 during the growing season since spring 2001. According to the results the soil is probably not yet much influenced by the fumigation of the tree crowns, and it is too early to estimate whether the observed nutrient effects are due to the CO2 treatment or to the natural variability of the soil
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