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| 3. |
- Andersson, Maria, 1980, et al.
(författare)
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Enhanced concentrations of dissolved gaseous mercury in the surface waters of the Arctic Ocean
- 2008
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 110:3-4, s. 190-194
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Tidskriftsartikel (refereegranskat)abstract
- During an almost three months long expedition in the Arctic Ocean, the Beringia 2005, dissolved gaseous mercury (DGM) was measured continuously in the surface water. The DGM concentration was measured using an equilibrium system, i.e. the DGM in the water phase equilibrated with a stream of gas and the gas was thereafter analysed with respect to its mercury content. The DGM concentrations were calculated using the following equation, DGM = Hg eq / k H' where Hg eq is the equilibrated concentration of elemental mercury in the gas phase and k H' is the dimensionless Henry's law constant at desired temperature and salinity. During the expedition several features were observed. For example, enhanced DGM concentration was measured underneath the ice which may indicate that the sea ice acted as a barrier for evasion of mercury from the Arctic Ocean to the atmosphere. Furthermore, elevated DGM concentrations were observed in water that might have originated from river discharge. The gas-exchange of mercury between the ocean and the atmosphere was calculated in the open water and both deposition and evasion were observed. The measurements showed significantly enhanced DGM concentrations, compared to more southern latitudes. © 2008 Elsevier B.V. All rights reserved.
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| 4. |
- Andersson, Maria, 1980, et al.
(författare)
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Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea
- 2007
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Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 104:3-4, s. 214-226
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg-extr / H', Hg-extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March-April 2004 and October-November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg-extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600-1150%) was observed during the summer. The spring showed the lowest variation (260-360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500-1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P. S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air-sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(l):373-387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m(-2) h(-1). The summer value was estimated to 22.3 pmol m(-2) h(-1) and the spring to 7.6 pmol m(-2) h(-1). Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons. (C) 2006 Elsevier B.V. All rights reserved.
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- Elfving, P, et al.
(författare)
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In situ IR study on the initial sulphition and carbonation of Ca(OH)(2) and CaO by SO2 polluted air
- 1996
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Ingår i: Atmospheric Environment. - 1873-2844 .- 1352-2310. ; 30:23, s. 4085-4089
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Tidskriftsartikel (refereegranskat)abstract
- Absorptions of SO2 and CO2 to fresh and aged forms of CaO and Ca(OH)2 are investigated at dry and humid conditions. Sulphite formation on Ca(OH)2 is found to be fairly independent of the relative humidity, while surface water is found to be a necessary condition for the corresponding carbonation reaction. Results supportive of Ca(OH)2 sulphition to be strongly preferred before carbonation at humid conditions are produced. Marked improvements in SO2 adsorption are seen for the fresh substrates. The observations are put in perspective of an on-going effort to understand the roles of SO2 in the deterioration of calcareous stone monuments, and are relevant to the chemistry of building materials.
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| 7. |
- Elfving, P, et al.
(författare)
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MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE .1. INITIAL SURFACE SULFITE FORMATION ON CALCITE
- 1994
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Ingår i: Applied Surface Science. - 0169-4332. ; 74:1, s. 91-98
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Tidskriftsartikel (refereegranskat)abstract
- An experimental set-up to investigate the reactions at ppm concentrations of pollutants with stone surfaces, involving a minimum of sample tampering, is proposed. In-situ Diffuse Reflectance Infrared Fourier Transform spectrometry (DRIFT) is employed to monitor the time evolution of products formed at a precipitated calcite sample. The powdered sample was exposed to a mixture of air and SO,(g) at different humidities. The nature of the initial sulphite formed is discussed in terms of anhydrous and hemihydrate calcium sulphite and sulphite in solution. In all three cases IR spectra are produced and compared to previous studies. The DRIFT spectra reveal the presence of at least two sulphite species on calcite at humid conditions, one chemisorbed and one dissolved. The relevance of this study to the understanding of calcareous stone deterioration is discussed.
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| 8. |
- Elfving, P, et al.
(författare)
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MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE .2. SULFATE FORMATION ON CALCITE
- 1994
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Ingår i: Applied Surface Science. - 0169-4332. ; 78:1, s. 83-92
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Tidskriftsartikel (refereegranskat)abstract
- The crucial role of surface water in the formation of surface sulphite was addressed in a previous study by in-situ Diffuse Reflectance Infrared Fourier Transform spectrometry (DRIFT). No sulphate was formed, indicating O2(g) to be too weak an oxidant to oxidize surface sulphite. The usefulness of DRIFT is further emphasized as it is employed to investigate the roles of NO2 and O3 in the formation of gypsum on calcareous stone at close to normal atmospheric conditions. Sulphate formation at calcite, employed to model e.g. marble, is shown to progress via a surface sulphite intermediate. NO2 is found to catalyze surface sulphate formation by activating molecular oxygen, while ozone acts to form sulphate by direct oxidation.
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| 9. |
- Elfving, P, et al.
(författare)
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MODEL STUDY OF THE 1ST STEPS IN THE DETERIORATION OF CALCAREOUS STONE .3. MANGANESE AND IRON-MEDIATED SULFATION OF NATURAL STONE
- 1994
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Ingår i: Applied Surface Science. - 0169-4332. ; 78:4, s. 373-384
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Tidskriftsartikel (refereegranskat)abstract
- Transition-metal-mediated sulphation of calcareous stone is investigated. Mixes of iron and manganese compounds with precipitated or ground calcite are employed to model natural calcareous stones containing these metals in trace concentrations. The products are characterized by Diffuse Reflectance Infrared Fourier Transform spectrometry. Sulphation is shown to depend strongly on the amounts of transition metals in the mixture, and calibration curves are constructed. Sulphate formations at natural calcareous stone surfaces are discussed within the framework of the assumed model.
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| 10. |
- Feng, Xinbin, et al.
(författare)
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Modified on-line monitoring of total gaseous mercury in flue gases using a Semtech 2000 Analyzer
- 2000
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Ingår i: Fresenius Journal of Analytical Chemistry. - 0937-0633. ; 368:5, s. 528-533
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Tidskriftsartikel (refereegranskat)abstract
- The Semtech Hg 2000 analyzer continuously monitors the Hg0 content in flue gas. An on-line measurement method of total gaseous mercury in flue gas developed in our laboratory is described, which uses the absorption cell of the Semtech Hg Analyzer connected to a converter that is located in a furnace heated up to 650 °C. The converter can be heated up to 800 °C by both the furnace and an extra heating of a Ni-Cr alloy heating wire. Both the absorption cell and the converter are made of quartz. All gaseous Hg2+ species in flue gas are thermally reduced to Hg0 by the converter and detected by the Semtech Hg 2000 analyzer. The thermal reduction efficiencies of different conversion materials, which were filled in the converter, such as quartz chips, granular MgO, Ni and CoO powder, were tested using different flue gas conditions. Studies have shown that HCl is the major factor to inhibit the thermal reduction of Hg2+ to Hg0, and in the converter and the absorption cell Hg0 will react readily with HCl to form HgCl2. Both MgO and Ni could be used in the converter to absorb HCl in the flue gas, but Ni has better absorption efficiency. By using an original Semtech and a modified one, both Hg0 and total gaseous Hg contents in flue gas could be monitored simultaneously and continuously.
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