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Träfflista för sökning "AMNE:(NATURAL SCIENCES Chemistry Environmental chemistry) ;conttype:(scientificother);spr:eng;srt2:(1995-1999)"

Sökning: AMNE:(NATURAL SCIENCES Chemistry Environmental chemistry) > Övrigt vetenskapligt/konstnärligt > Engelska > (1995-1999)

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1.
  • Öberg, Tomas, 1956- (författare)
  • Replacement of PCBs (polychlorinated biphenyls) and HCB (hexachlorobenzene) : the Swedish experience
  • 1996
  • Ingår i: Alternatives to persistent organic pollutants. - Solna : Kemikalieinspektionen. - 9923050106
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • The total import to Sweden of PCB between 1957-1980 has been estimated to 8,000-10,000 metric tonnes. A substantial part of the import, probably more than 50% was re-exported in goods. The use of PCB in Sweden has been restricted since 1972, and in 1978 it was decided that no new permits to use PCB in new products should be issued. Remaining part in the power sector of the industry has also been removed. Transformers or capacitors containing PCB and with a higher rating than two kilovoltamperes (reactive) may not be used after the 31st of December 1994. PCB containing transformers were never manufactured in Sweden. The problem with PCB filled transformers and contaminated transformer oils has therefore been less severe, compared to many other industrialized countries. The main chemical alternative to PCB in transformers is mineral oil with different additives. PCB was used in the manufacture of capacitors in Sweden before 1978. The use for this purpose accounted for about 80% of the import of PCB. Chemical alternatives for PCB as capacitor fluid include a multitude of chemical compounds. The capacitor fluid most frequently used today in Sweden is a mixture of methyl(phenylmethyl)benzene and methylbis(phenylmethyl)benzene. PCB was used in different building materials as a plasticiser. Chemical alternatives include chlorinated paraffins and phthalates. Chlorinated paraffins are however replaced due to environ-mental concerns, and it has also been decided to phase out the phthalates. Substantial amounts of PCB, an estimated 190-650 metric tonnes, still remain in buildings. It is obvious that measures to deal with these problems may cost many times more than the replacement already accomplished. Destruction capability and capacity are keys to a successful and final solution to the PCB problem. The destruction cost is also the major cost factor in the replacement. 17,667 metric tonnes of PCB containing waste was received by SAKAB, the Swedish hazardous waste treatment plant, between 1987-1995. This gives an idea of how much PCB wastes that have to be handled. Minor amounts of HCB (hexachlorobenzene) has been used in some parts of the Swedish industry. HCB has not been manufactured in Sweden and previous use has been replaced. Estimates of the international production are contradictory. It therefore seems premature to neglect HCB as an organic micro-pollutant of environmental concern.
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2.
  • Shen, Yin (författare)
  • On-line Sample Pretreatment Based on Membrane Enrichment, Mainly Using Supported Liquid Membranes, for Chromatographic Analysis
  • 1997
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The main objective of this work was to construct practical analytical systems for the analysis of environmental and biological samples, using membrane-based techniques for sample pretreatment and chromatography for final analysis. Two types of membrane processes have been applied, with emphasis on automation. The supported liquid membrane (SLM) extraction was carried out in an automated continuous flow system coupled to ion-exclusion chromatography (IEC) for the determination of volatile carboxylic acids in air. Another totally automated system, using the SLM coupled on-line to anion-exchange chromatography, was developed for the determination of low-molecular weight organic acids in soil samples. Several short precolumns were co-ordinated with the SLM enrichment system to remove interfering compounds. The system has been used for routine measurements. The SLM extraction was combined with capillary gas chromatography (GC) for the determination of local anaesthetics in untreated blood plasma samples. A solid phase column was located between the SLM unit and GC unit as a interface for phase switching. The system was fully automated and permitted the analysis of ca 50 samples per day. Microporous membrane liquid-liquid extraction (MMLLE), combined with capillary GC quantitation, was presented for treating complex samples. The local anaesthetics were used as model compounds both in aqueous solutions and in blood plasma. The method can be used for routine measurements of the analytes in plasma at sub ppm level. In this thesis, a general overview of different membranes and membrane processes, in particular SLM, and their applications of sample preptreatment are given. The applications of membrane-based sample preparation for on-line coupling with liquid chromatography and gas chromatography are discussed. Finally a brief discussion about automation of analysis is given.
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3.
  • Bergbäck, Bo, et al. (författare)
  • Metals in society
  • 1997. - 1
  • Ingår i: The global environment. - Oslo : Scandinavian Science Publ.. - 352728771X ; , s. 276-289
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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4.
  • Feng, Xinbin, et al. (författare)
  • On-line speciation of mercury in flue gas
  • 1999
  • Ingår i: Book of Abstract. 5th International Conference on Mercury as a Global Pollutant, Rio de Janeiro, Brazil, 1999.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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5.
  • Skoglundh, Magnus, 1965 (författare)
  • New Materials in Environmental Catalysis
  • 1995
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis presents new approaches to the control of emissions within the field of environmental catalysis. Three catalytic systems; bimetallic catalysts, perovskites and promoted catalysts have been prepared and evaluated for complete oxidation of volatile organic compounds and for simultaneous conversion of CO, hydrocarbons and nitrogen oxides. The activities for complete oxidation of CO and hydrocarbons over coimpregnated Pd-Pt catalysts did not vary linearly with the Pd:Pt-ratio. This non-linear variation strongly implies that bimetallic Pd-Pt clusters are formed in such catalysts. Maxima in activity for oxidation of xylene and CO were reached over Pd0.8Pt0.2/Al2O3. The activity increased with increasing total noble metal content, decreasing reactant concentration and increasing oxygen concentration. Catalysts with supports of .gamma.-Al2O3, hydrothermally treated (814 °C, 100% steam) prior to impregnation with noble metal complexes, exhibited higher activity for oxidation of xylene than those having thermally (550 °C, air) treated supports. Using a technique with repeated impregnations and subsequent calcinations at 900 °C, a barrier layer, which acted as a precursor or support for perovskite formation, was created on alumina when impregnated with La3+, Sr2+, Cu2+ and Ru3+. A perovskite phase of the nominal composition La1-xSrxAl1-2yCuyRuyO3 was formed in increasing amount with increasing content of Sr and Ru in the stock solutions used. The presence of Sr and Ru seemed to retard formation of La2CuO4 and promote formation of the perovskite phase. Cu was well dispersed over the entire support while Ru was found only in the grains of the perovskite phase. The perovskite phase seemed to take an active part in the simultaneous conversion of NO, CO and C3H6. Promoting complex metal oxides based on Cu or Co, having the overall metal composition La0.45Sr0.15Ce0.35Zr0.05M1.0 (M=Cu or Co), with small amounts of Pt-Rh, yielded high activity for the simultaneous conversion of CO, C3H6 and NO. Addition of 4.4 micromol Pt-Rh to La0.45Sr0.15Ce0.35Zr0.05Co/Al2O3 yielded a three-way activity quite similar to that obtained over a commercial three-way catalyst containing more than four times as much Pt-Rh. Pd/Al2O3 exhibited three-way activity in a narrow interval around the stoichiometric balance between oxidizing and reducing gases. Addition of La or Co to Pd broadened this interval under net reducing conditions. The conversions of CO and C3H6 started at about 100 °C lower temperatures over Pd/Co/La/Bl2O3 compared with Pd/La/Al2O3. The conversion of NO under transient conditions was markedly increased over Co-promoted Pd compared with unpromoted Pd.
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7.
  • Andersson, Eva, 1967- (författare)
  • Hydrothermal alteration of organic matter at spreading centers
  • 1998
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Alteration of organic matter, mainly amino acids, at sub-seafloor hydrothermal conditions has been investigated by performing laboratory experiments and by studying deep-sea sediments from hydrothermally active areas on the northern Juan de Fuca Ridge, northeast Pacific Ocean.Quaternary sediments from Middle Valley and the eastern flank of the Juan de Fuca Ridge recovered during the Ocean Drilling Program Legs 139 and 168 have been analyzed for total hydrolyzable amino acid concentrations, individual amino acid abundances and stereochemistry in order to evaluate the effects of hydrothermal stress on the decomposition of sedimentary amino acids. In near surface sediments, amino acids account for up to 3.3% of the total organic carbon content and up to 12% of the total nitrogen content. The non-protein amino acid b-alanine and g-aminobutyric acid become increasingly abundant with depth in low temperature holes (Leg 168) as a result of enzymatic decarboxylation of aspartic acid and glutamic acid, respectively. The decomposition of amino acid in high temperature holes (Leg 139) is enhanced with depth and the amino acid patterns indicates that most amino acids are incorporated into geopolymers and that condensation results in increased stability of some amino acids.The effects of low temperature hydrothermal activity on microbially mediated organic matter diagenesis were studied by comparing depth concentration profiles of interstitial sulfate and methane of Holes 1023A, 1024B, 1025B and 1028A, ODP Leg 168. Diffusional exchange between sulfate-rich basement fluids and pore-waters increases the interstitial sulfate concentrations with depth below local sulfate minima caused by bacterial sulfate reduction. The effects of diffusional processes on pore-water chemistry in the sediment column is reflected by the inhibition of methane production and is largely dependent on sediment thickness.The decomposition of alanine, leucine, aspartic acid and serine in aqueous solutions was studied at 200oC and 50 bar with the purpose of evaluating the effect dissolved oxygen on decomposition rates. The redox buffering mineral assemblage pyrite-pyrrhotite-magnetite was used to constrain the oxygen fugacity to geologically realistic values. Comparisons between results obtained from buffered and nonbuffered runs show that the decomposition is faster for most amino acids but serine in nonbuffered experiments.
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9.
  • Sellström, Ulla, 1956- (författare)
  • Determination of some polybrominated flame retardants in biota, sediment and sewage sludge
  • 1999
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Brominated flame retardants (BFRs) are mainly used in different polymers, and can be released to the environment during industrial processes, during the entire life-time of the flame-retarded product and after disposal. The aim of the present study was to gain knowledge about occurrence and concentrations of some BFRs in the environment, to search for sources for these chemicals and to investigate changes in concentrations over time. The emphasis was on the polybrominated diphenyl ethers (PBDE), but hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA) were also studied to some extent.The analytical method used was mass spectrometry run in the electron capture negative ionisation (ECNI) mode. The formation of bromide ions was utilised as a sensitive and selective detection method for the brominated compounds.BFRs seem to be ubiquitous contaminants in the environment. Long range transport in air may explain the contamination of PBDE in whitefish from the pristine mountain lake Storvindeln. The highest concentrations are found in samples collected in the vicinity of industrial (textile and polymer) activities, where they are/have been used. Samples from heavily populated areas contain higher concentrations of PBDE than samples from remote areas, which results in a south-north geographical trend in concentrations. Generally the concentrations are higher in aquatic organisms than in those from terrestrial environments. Municipal sewage sludge, which reflects the current use of chemicals in society, contains all the BFRs covered in this thesis.DecaBDE was only indicated in biota, but was found in high concentrations in sediment. Higher concentrations of tetra- and pentaBDE in piscivorous birds and mammals compared to the fish they eat indicate biomagnification of these substances. HBCD was found in both fish and sediment from the Rivers Viskan/Häggån, where it has been used to some extent as a substitute for decaBDE in the textile industry. HBCD was also detected in guillemot eggs from a background area in the Baltic Sea.Increasing concentrations over time of tetra- and pentaBDE was first indicated in a sediment core from the Baltic Sea, sampled in 1987. This increase was later confirmed in guillemot eggs from the island Stora Karlsö in the Baltic, but from the mid-late 1980s, the concentrations started to decrease in this species. This decrease is not in agreement with the results from other studies, indicating different sources of contamination.
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10.
  • Fabrichnaya, Olga (författare)
  • Thermodynamic study of the FeO-MgO-Al2O3-SiO2 system : Data assessment and phase diagram calculation
  • 1998
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This dissertation consists of assessed thermodynamic properties for phases in the geologically and industrially important system Fe-Mg-Al-Si-O and calculated phase diagrams. Mathematical processing of different kinds of experimental data (phase equilibrium data, calorimetric, volumetric, thermophysical,electrochemical, activity data) is used to derive internally consistent thermodynamic database. The Murnaghan equation of state is used to describe the pressure-volume-temperature (P-V-T) relations in the end members and stoichiometric phases. Thermal expansion, compressibility and pressure derivative of bulk modulus are considered as temperature dependent. Sublattice model is applied to describe solid and liquid solutions and Redlich-Kister model is used for interaction between species on a sublattice.Thermodynamic data for solid phases in the Fe-Si-O system are optimized to reproduce phase relations at temperatures up to 2000 K and pressures between 1 bar and 20 GPa. Parameters for liquid phases in the Fe-Si-O system are assessed from solid-liquid equilibria at 1 bar. Because of lack of high pressure experimental data for liquid, melting relations at high pressures are calculated only in thesubsystems Fe-FeO, SiO2 and Fe2SiO4.Thermodynamic parameters for solid phases in the system FeO-MgO-Al2O3-SiO2 are assessed and subsolidus phase relations are calculated at pressures up to 30 GPa. The calculated phase diagram for pyrolite composition are used to explain seismic discontinuities in the Earth's mantle. The 400 km discontinuity could be attributed to garnet+olivine+β-spinel+hp-clinopyroxene divariant zone. The seismic boundary at 650-680 km could be related to two very narrow fields of ilmenite=perovskite and γ-spinel=perovskite+magnesiowustite transitions. Other seismic discontinuities could be assigned to phase transformations occurring at 450 km (complete dissolution of pyroxene in garnet), at 500-520 km (β-spinel+γ-spinel zone), and at 600 km (γ-spinel+stishovite+ilmenite or garnet+ilmenite zones). Garnet disappears at 730-750 km and the assemblage perovskite+magnesiowustite is stable below.
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