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Sökning: hsv:(NATURVETENSKAP) hsv:(Geovetenskap och miljövetenskap) hsv:(Meteorologi och atmosfärforskning) > (2000-2004)

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1.
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2.
  • Bockgård, Niclas, et al. (författare)
  • Accuracy of CFC groundwater dating in a crystalline bedrock aquifer: Data from a site in southern Sweden
  • 2004
  • Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 12:2, s. 171-183
  • Tidskriftsartikel (refereegranskat)abstract
    • The concentrations of chlorofluorocarbons (CFC-11, CFC-12, and CFC-113) and tritium were determined in groundwater in fractured crystalline bedrock at Finnsjon, Sweden. The specific goal was to investigate the accuracy of CFC dating in such an environment, taking potential degradation and mixing of water into consideration. The water was sampled to a depth of 42 m in three boreholes along an 800-m transect, from a recharge area to a local discharge area. The CFC-113 concentration was at the detection limit in most samples. The apparent recharge date obtained from CFC-11 was earlier than from CFC-12 for all samples, with a difference of over 20 years for some samples. The difference was probably caused by degradation of CFC-11. The CFC-12 dating of the samples ranged from before 1945 to 1975, with the exception of a sample from the water table, which had a present-day concentration. Conclusions about flow paths or groundwater velocity could not be drawn from the CFCs. The comparison between CFC-12 and tritium concentrations showed that most samples could be unmixed or mixtures of waters with different ages, and the binary mixtures that matched the measured concentrations were determined. The mixing model approach can be extended with additional tracers.
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3.
  • Olsson, Mikael, 1948, et al. (författare)
  • Mäta vatten : Undersökningar av sött och salt vatten
  • 2003
  • Bok (övrigt vetenskapligt/konstnärligt)abstract
    • boken presenterar principer för kemiska, fysikaliska och biologiska undersökningar av sött och salt vatten. Boken ger teori och praktik kring en rad mätvariabler och mätmetoder samt hänvisningar till officiella metodbeskrivningar. Kemiska, biologiska och hydrologiska samband i hav, sjöar och vattendrag förklaras. Mäta vatten är en guide för att tolka mätvärden i sjöar, vattendrag och hav. ”Normala” värden anges liksom gränsvärden för dricksvatten. I unika diagram och kartor sammansställs mätvärden för 27 olika variabler, baserade på mätningar i fyra tusen sjöar. Med aktuella mätvärden kan du i dessa diagram bedöma din sjös status, och jämföra med andra sjöar i Sverige. I boken finns bland mycket annat också ett lexikografiskt uppslag vilket visar vattenomsättningen runt Sveriges kuster.
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5.
  • Mellqvist, Johan, 1965 (författare)
  • Flare testing using the SOF method at Borealis Polyethylene in the summer of 2000
  • 2001
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A study of flaring efficiency at the Borealis low-pressure plant in Stenungsund was conducted using a new patented method called Solar Occultation Flux (SOF), in combination with a new type of direct measurement of flow rate and ethylene concentration in the flare stack. The SOF method is based on the measurement of hydrocarbon concentrations over a cross-section of the emission plume. Multiplied by wind speed, this gives the flux of gas through the cross-section, i.e., the source emission in kg·s-1. In the measurements, the sun was used as the light source. An infrared FTIR spectrometer linked to a sun tracker was placed on top of a van that was driven in such a way that the sunlight shone through a cross-section of the plume being measured. From the size of the molecular fingerprints in the infrared solar spectra, the concentration of ethylene and other constituents can be calculated.The results show that the flare we studied has a good combustion efficiency of about 98% at high loads (>1100 kg·h -1), but that at low loads, which are the normal operating conditions most of the time, it has a significantly lower efficiency (50-90%). Emissions thus appear to vary between 20 and 50 kg/h irrespective of load – a result that is consistent with other long-term FTIR measurements taken outside the plant. Similar emission results were also obtained during the course of the project from a newly installed flare, so that the problem does not appear to be specific to the flare that we studied.From the measurements in this study it can be concluded that a major contributing factor in the poor efficiency is an overdose of steam at low operating loads, as a result of trying to avoid soot formation by optimizing flare combustion at high loads. The problem can presumably be solved by introducing some form of dynamic steam metering linked to combustion load, or by eliminating the presence of ethylene at low operating loads. The direct flare stack measurements show that the heating value is generally low, and that theoretically we could therefore expect poorer efficiency levels. It was not possible to demonstrate this unambiguously in the present study, however, since the steam and ethylene levels were generally covariant. Only in a few cases did we find a low efficiency at low ethylene concentration, independent of steam quantity.
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6.
  • Gårdfeldt, Katarina, 1959, et al. (författare)
  • A kinetic study on the Abiotic Methylation of Divalent Mercury in the Aqueous phase
  • 2003
  • Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 304:1-3, s. 127-136
  • Tidskriftsartikel (refereegranskat)abstract
    • The mechanism and kinetics of the formation of methylmercury from an experimental solution containing divalent mercury and acetic acid has been investigated. The experiments were performed in a 2-dm3 Teflon reactor. The organic mercury was measured with time resolutions varying between minutes and hours, after derivatisation, gas chromatography separation and Cold vapour atomic fluorescence detection. (GC)-CVAFS. CVAFS technique was used for determination of inorganic mercury in the aqueous phase using an automated mercury analyser. The experiments were carried out in concentrations relevant for natural waters. Our result shows that the reaction proceeds via mercury acetate complexes. A first order reaction coefficient has been calculated at various pH values, and was found to be (9.0±0.9)×10−7 s−1 at pH 3.6–3.7. The rate was not found to be enhanced by UV-light when taking into account the photolytical degradation of methylmercury. The reaction rate at various pH values, the influences of some other relevant reaction parameters, and implications for atmospheric and terrestrial waters are discussed.
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7.
  • Gårdfeldt, Katarina, 1959, et al. (författare)
  • Evasion of Mercury from coastal and open waters of the Atlantic ocean and the Mediterranean sea
  • 2003
  • Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 37:Suppl 1, s. S73-S84
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissolved gaseous mercury (DGM) was measured in coastal Atlantic seawater and in the Mediterranean Sea. The Atlantic measurements were performed during September 1999 at the Mace Head Atmospheric Research Station, situated on the Irish west coast. The measurements in the Mediterranean Sea were made along a 6000 km cruise path from 14 July to 9 August 2000 in the framework of the Med-Oceanor project. Total gaseous mercury (TGM) concentrations in air were continuously measured with a 5 min time resolution using an automated mercury analyser (Tekran 2537A) during both expeditions. Paired TGM and DGM samples from all campaigns showed that the surface water was supersaturated with elemental mercury. The mercury evasion was estimated using a gas exchange model (J. Geophys. Res. 97 (1992) 7373), which uses salinity, wind speed and water temperature as independent parameters. The predicted average mercury evasion from the coastal Atlantic water was 2.7 ng m−2 h−1 implying that the concentration of TGM in the Atlantic air is enhanced by mercury evasion from the sea. Measurements in different regions of the Mediterranean Sea showed spatial variations in DGM concentrations. The highest DGM concentration (90 pg l−1) was observed at a location in the Strait of Sicily (37°16N 11°52E). The mercury evasion in the eastern sector of the Mediterranean Sea (area: 32–36°N, 17–28°E) was generally higher (7.9 ng m−2 h−1) than that observed in the Tyrrhenian Sea (4.2 ng m−2 h−1) or in the western sector (2.5 ng m−2 h−1) (areas: 38–42°N, 8–13°E and 38–41°N, 7–8°E, respectively). Estimations of mercury evasion were also made at Mediterranean coastal sites using a dynamic chamber technique. In addition, a newly developed method making continuous in situ DGM measurements possible was tested.
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8.
  • Gårdfeldt, Katarina, 1959, et al. (författare)
  • Oxidation of atomic mercury by hydroxyl radicals and photoinduced decomposition of methylmercury species in the aqueous phase
  • 2001
  • Ingår i: Atmospheric Environment. - 1352-2310 .- 1873-2844. ; 35:17, s. 3039-3047
  • Tidskriftsartikel (refereegranskat)abstract
    • The rate constant for Hg0+.OH, kHg0+.OH=(2.4±0.3)×109 M−1 s−1, in the aqueous phase was determined using a relative rate technique with methyl mercury as reference compound. The .OH initiated mercury reaction proceeds via the molecular Hg(I) radical which is oxidised to Hg(II) by dissolved O2. The reaction can be of importance under certain atmospheric circumstances, such as when the aqueous phase capacity of forming OH radicals is significant and the gas phase concentration of ozone drops. The same end product, i.e. Hg(II) was observed from the photodegradation of methylmercury hydroxide. In this case, molecular Hg(I) radicals are again likely to be formed after photodegradation of the Hg–C bond with subsequent oxidation. A lifetime of 230 h of methylmercury at outdoor conditions was estimated due to this reaction. The action of .OH on methylmercury species also involves breaking of organometallic bonds and formation of Hg(II). Speciation of these reaction products from methylmercury is important for the estimation of biogeochemical cycling of mercury.
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9.
  • Hazenkamp-Von Arx, M.E., et al. (författare)
  • PM2.5 and NO2 assessment in 21 European study centres of ECRHS II : annual means and seasonal differences
  • 2004
  • Ingår i: Atmospheric Environment. - : Elsevier. - 1352-2310 .- 1873-2844. ; 38:13, s. 1943-1953
  • Tidskriftsartikel (refereegranskat)abstract
    • The follow-up of cohorts of adults from more than 20 European centres of the former ECRHS I (1989-1992) investigates long-term effects of exposure to ambient air pollution on respiratory health, in particular asthma and change of pulmonary function. Since PM2.5 is not routinely monitored in Europe, we measured PM2.5 concentrations in 21 participating centres to estimate 'background' exposure in these cities. Winter (November-February), summer (May-August) and annual mean (all months) values of PM2.5 were determined from measuring periods between June 2000 and November 2001. Sampling was conducted for 7 days per month for a year. Annual and winter mean concentrations of PM2.5 vary substantially being lowest in Iceland and highest in centres in Northern Italy. Annual mean concentrations ranged from 3.7 to 44.9 mug m(-3), winter mean concentrations from 4.8 to 69.2 mug m(-3), and summer mean concentrations from 3.3 to 23.1 mugm(-3). Seasonal variability occurred but did not follow the same pattern across all centres. Therefore, ranking of centres varied from summer to winter. Simultaneously, NO2 concentrations were measured using passive sampling tubes. Annual mean NO2 concentrations range from 4.9 to 72.1 mug m(-3) with similar seasonal variations across centres and constant ranking of centres between seasons. The correlation between annual NO2 and PM2.5 concentrations is fair (Spearman correlation coefficient r(s) = 0.75), but when considered as monthly means the correlation is far less consistent and varies substantially between centres. The range of PM2.5 mass concentrations obtained in ECRHS II is larger than in other current cohort studies on long-term effects of air pollution. This substantial variation in PM2.5 exposure will improve statistical power in future multilevel health analyses and to some degree may compensate for the lack of information on within-city variability. Seasonal means may be used to indicate potential differences in the toxicity across the year. Across ECRHS cities annual NO2 might serve as a surrogate for PM2.5, especially for past exposure assessment, when PM2.5 is not available.
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