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Measurements of Trace Substances in the Arctic Troposphere as Potential Precursors and Constituents of Arctic Haze (1999)

Jaeschke, W. ; Salkowski, T. ; Dierssen, J. P. ; [et al.]

Springer

Journal of atmospheric chemistry 34 (1999), S. 291-319

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ISSN: 1573-0662

Keywords: arctic air pollution ; precursor substances ; vertical profiles ; ozone ; PAN ; SO2 ; gaseous HNO3 ; particulate nitrate ; sulfate ; ammonium

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Geosciences

Notes: Abstract During two measuring campaigns in early spring 1994 and 1995 (March/April) and one campaign in summer 1994, measurements of ozone, PAN, sulfur dioxide, nitric acid, and particulate nitrate, sulfate, and ammonium (only 1995) were recorded in the Arctic. Observations were made by aircraft at various sites in the eastern and western Arctic. Ozone concentrations showed a steady increase with altitude both in spring and summer. During five flights in springtime, low ozone events (LOEs) could be observed near the surface and up to altitudes of 2000 m. SO2 background concentrations, ranging from detection limit (0.5 nmol/m3) to 5 nmol/m3, were observed during both spring and summer. Distinct maxima up to 55 nmol/m3 in lower altitudes were only obtained in springtime. Concentrations of the organic nitrate PAN were within a similar range as those of the inorganic nitrate HNO3 during spring campaigns. In contrast, concentrations of particulate nitrate were one half an order of magnitude lower. HNO3 concentrations increased significantly with altitude. Evidently, HNO3 was intruded from the stratosphere into the troposphere. Sulfate concentrations ranged between 5 and 30 nmol/m3; ammonium concentrations were obtained within a range from 10 to 50 nmol/m3.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006277230042

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Effects of diffusion limitation on immobilized nitrifying microorganisms at low temperatures (1995)

Wijffels, R. H. ; Hunik, J. H. ; Leenen, E. J. T. M. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 45 (1995), S. 1-9

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ISSN: 0006-3592

Keywords: nitrification ; immobilized cells ; activation energy ; diffusion limitation ; temperature ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Activation energies of suspended and immobilized nitrifying bacteria were determined and compared to determine if diffusion limitation results in decreased sensitivity for temperature. The activation energy for the respiration activity of suspended Nitrosomonas europaea and Nitrobacter agilis was found to be 86.4 and 58.4 kJ mol-1, respectively. The activation energy for oxygen diffusion in the support material, κ-carrageenan, determined from the effect of temperature on the effective diffusion coefficient (D), was 17.2 kJ mol-1. Consequently, the apparent actvation energy of diffusion limited cells should be lower. It was indeed shown that due to the effect of diffusion limitation and to temperature effects on the Monod constant Ks, the immobilized-cell activity was less sensitive to temperature. The apparent activation energy for immobilized Ns. europaea was between 28.6 and 94.2 kJ mol-1 and for immobilized Nb. agilis between 1.4 and 72.9 kJ mol-1, depending on the oxygen concentration and temperature. © 1995 John Wiley & Sons, Inc.

Additional Material: 8 Ill.