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Characterization of Positive Air Ions in Boreal Forest Air at the Hyytiälä Smear Station : Volume 7, Issue 4 (03/07/2007)

By Hõrrak, U.

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Book Id: WPLBN0003998076
Format Type: PDF Article :
File Size: Pages 53
Reproduction Date: 2015

Title: Characterization of Positive Air Ions in Boreal Forest Air at the Hyytiälä Smear Station : Volume 7, Issue 4 (03/07/2007)  
Author: Hõrrak, U.
Volume: Vol. 7, Issue 4
Language: English
Subject: Science, Atmospheric, Chemistry
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2007
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Komsaare, K., Salm, J., Aalto, P. P., Mäkelä, J. M., Tammet, H., Laakso, L.,...Kulmala, M. (2007). Characterization of Positive Air Ions in Boreal Forest Air at the Hyytiälä Smear Station : Volume 7, Issue 4 (03/07/2007). Retrieved from http://ebooklibrary.org/


Description
Description: Institute of Physics, University of Tartu, 18 Ülikooli St., 50090 Tartu, Estonia. The behavior of the concentration of positive small (or cluster) air ions and naturally charged nanometer aerosol particles (aerosol ions) has been studied on the basis of measurements carried out in a boreal forest at the Hyytiälä SMEAR station, Finland, during the BIOFOR III campaign in spring 1999. Statistical characteristics of the concentrations of cluster ions, two classes of aerosol ions of the sizes of 2.5–8 nm and 8–ca. 20 nm and the quantities that determine the balance of small ions in the atmosphere have been given for the nucleation event days and non-event days. The dependence of small ion concentration on the ion loss (sink) due to aerosol particles was investigated applying a model of bipolar diffusion charging of particles by small ions. The small ion concentration and the ion sink were closely correlated (correlation coefficient –87%) when the fog events and the hours of high relative humidity (above 95%), as well as nocturnal calms and weak wind (wind speed <0.6 m s−1) had been excluded. However, an extra ion loss term presumably due to small ion deposition on coniferous forest with a magnitude equal to the average ion loss to pre-existing particles is needed to explain the observations. Also the hygroscopic growth correction of measured aerosol particle size distributions was found to be necessary for proper estimation of the ion sink. In the case of nucleation burst events, variations in the concentration of small positive ions were in accordance with the changes caused by the ion sink due to aerosols; no clear indication of positive ion depletion by ion-induced nucleation was found. The estimated average ionization rate of the air at the Hyytiälä station in early spring, when the ground was partly covered with snow, was about 6 ion pairs cm−3 s−1. The study of the charging state of nanometer aerosol particles (2.5–8 nm) revealed a strong correlation (correlation coefficient 88%) between the concentrations of particles and positively charged particles (positive air ions) during nucleation bursts. The estimated charged fraction of particles, which varied from 3% to 6% considering various nucleation event days, confirms that these particles are almost quasi-steady state charged. Also the particles and air ions in the size range of 8–ca. 20 nm showed a good qualitative consistency; the correlation coefficient was 92%.

Summary
Characterization of positive air ions in boreal forest air at the Hyytiälä SMEAR station

Excerpt
Aalto, P., Hämeri, K., Becker, E., Weber, R., Salm, J., Mäkelä, J. M., Hoell, C., O'Dowd, C. D., Karlsson, H., Hansson, H.-C., Väkevä, M., Koponen, I., Buzorius G., and Kulmala M.: Physical characterization of aerosol particles during nucleation events, Tellus, 53B, 344–258, 2001.; Beig, G. and Brasseur, G. P.: Model of tropospheric ion composition: A first attempt, J. Geophys. Res. 105, 22 671–22 684, 2000.; Birmili, W., Berresheim, H., Plass-Dülmer, C., Elste, T., Gilge, S., Wiedensohler, A., and Uhrner, U.: The Hohenpeissenberg aerosol formation experiment (HAFEX): A long-term study including size-resolved aerosol, H2SO4, OH, and monoterpenes measurements, Atmos. Chem. Phys., 3, 361–376, 2003.; Birmili, W., Schwirn, K., Nowak, A., Petäjä, T., Rose, D., Hämeri, K., Aalto, P., Wiedensohler, A., Kulmala, M., and Boy, M. Hygroscopic growth of particle number size distributions at the atmospheric research station Hyytiälä, Finland, Report Series in Aerosol Science (Helsinki), 81A, 62–67, 2006.; Chalmers, J. A.: Atmospheric Electricity, Pergamon Press, Oxford, London, 1967.; Dolezalek, H.: The atmospheric electric fog effect, Rev. Geophys., 1(2), 231–282, 1963.; Eisele, F. L. and Tanner, D. J.: Identification of ions in continental air, J. Geophys. Res., 95, 20 539–20 550, 1990.; Froyd, K. D. and Lovejoy, E. R.: Experimental thermodynamics of cluster ions composed of H2SO4 and H2O. 1. Positive ions, J. Phys. Chem. A, 107, 9800–9811, 2003a.; Froyd, K. D. and Lovejoy, E. R.: Experimental thermodynamics of cluster ions composed of H2SO4 and H2O. 2. Measurements and ab initio structures of negative ions, J. Phys. Chem. A, 107, 9812–9824, 2003b.; Fuchs, N. A. and Sutugin, A. G.: High-dispersed aerosols, in: Topics in Current Aerosol Research, edited by: Hidy, G. M. and Brock, J. R., vol. 2, pp. 1–60, Pergamon, Oxford, 1971.; Hanson, D. R. and Eisele, F. L.: Measurement of prenucleation molecular clusters in the NH3, H2SO4, H2O system, J. Geophys. Res., 107(D12), 4158, doi:10.1029/2001JD001100, 2002.; Hari, P. and Kulmala, M.: Station for Measuring Ecosystem–Atmosphere Relations (SMEAR II), Boreal Environ. Res., 10, 315–322, 2005.; Hatakka, J., Paatero, J., Viisanen, Y., and Mattsson, R.: Variations of external radiation due to meteorological and hydrological factors in central Finland, Radiochemistry, 40(6), 515–519, MAIK Nauka/ Interperiodica Publishing, 1998.; Hirsikko, A., Laakso, L, Hõrrak, U., Aalto, P. P., Kerminen, V.-M., and Kulmala, M.: Annual and size dependent variation of growth rates and ion concentrations in boreal forest, Boreal Env. Res., 10, 357–369, 2005; Hoppel, W. A.: Ion-aerosol attachment coefficients, ion depletion, and the charge distribution on aerosols, J. Geophys. Res., 90, 5917–5923, 1985.; Hoppel, W. A. and Frick, G. M.: Ion-aerosol attachment coefficients and the steady-state charge distribution on aerosols in a bipolar ion environment, Aerosol Sci. Technol., 5, 1–21, 1986.; Hoppel, W. A. and Frick, G. M.: The nonequilibrium character of the aerosol charge distributions produced by neutralizers, Aerosol Sci. Technol., 12, 471–496, 1990.; Hoppel, W. A., Anderson, R. V., and Willett, J. C.: Atmospheric electricity in the planetary boundary layer, In: The Earth's Electrical Environment, National Academy Press, Washington, D.C., 149–165, 1986.; Hõrrak, U., Salm, J., and Tammet, H.: Bursts of intermediate ions in atmospheric air, J. Geophys. Res., 103, 13 909–13 915, 1998a.; Hoppel, W. A., Frick, G. M., Fitzgerald, J. W., and Larson, R. E.: Marine boundary layer

 

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