ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-5327-2008 Mode resolved density of atmospheric aerosol particles Kannosto J. 1 Virtanen A. 1 Lemmetty M. 1 Mäkelä J. M. 1 Keskinen J. 1 Junninen H. 2 Hussein T. 2 Aalto P. 2 Kulmala M. 2 Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, P.O. Box 692, 33101 Tampere, Finland Department of Physics, University of Helsinki, P.O. Box 64, 00014 Uhel, Finland 08 09 2008 8 17 5327 5337 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/8/5327/2008/acp-8-5327-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/5327/2008/acp-8-5327-2008.pdf

In this study, we investigate the mode resolved density of ultrafine atmospheric particles measured in boreal forest environment. The method used here enables us to find the distinct density information for each mode in atmospheric fine particle population: the density values for nucleation, Aitken, and accumulation mode particles are presented. The experimental data was gained during 2 May 2005–19 May 2005 at the boreal forest measurement station "SMEAR II" in Hyytiälä, Southern Finland. The density values for accumulation mode varied from 1.1 to 2 g/cm<sup>3</sup> (average 1.5 g/cm<sup>3</sup>) and for Aitken mode from 0.4 to 2 g/cm<sup>3</sup> (average 0.97 g/cm<sup>3</sup>). As an overall trend during the two weeks campaign, the density value of Aitken mode was seen to gradually increase. With the present method, the time dependent behaviour of the particle density can be investigated in the time scale of 10 min. This allows us to follow the density evolution of the nucleation mode particles during the particle growth process following the nucleation burst. The density of nucleation mode particles decreased during the growth process. The density values for 15 nm particles were 1.2–1.5 g/cm<sup>3</sup> and for grown 30 nm particles 0.5–1 g/cm<sup>3</sup>. These values are consistent with the present knowledge that the condensing species are semi-volatile organics, emitted from the boreal forest.

 References 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. K., Buzorius, G., and Kulmala, M.: Physical characterization of aerosol particles during nucleation events, Tellus, 53B, 344–358, 2001. Alam, A., Shi, J. P., and Harrison, R. M.: Observations of new particle formation in urban air, J. Geophys. Res., 108, D3, 4093, doi:10.1029/2001JD001417, 2003. Allan, J. D., Alfarra, M. R., Brower, K. N., Coe, H., Jayne, J. T., Worsnop, D. R., Aalto, P. P., Kulmala, M., Hyötyläinen, T., Cavalli, F., and Laaksonen, A.: Size and composition measurements of background aerosol and new particle growth in a Finnish forest during QUEST 2 using an Aerodyne Aerosol Mass Spectrometer, Atmos. Chem. Phys., 6, 315–327, 2006. Allen, J. O., Durant, J. L., Dookeran, N. M., Taghizadeh, K., Plummer, E. F., Lafleur, A. L., Sarofim, A. F., and Smith, K. A.: Measurement of C$_24$H$_14$ Polycyclic Aromatic Hydrocarbons Associated with a Size-Segregated Urban Aerosol, Environ. Sci. Technol., 32, 13, 1928–1932, 1998. Cass, G. R., Hughes, L. A., Bhave, P., Kleeman, M. J., Allen, J. O., and Salmon, L. G.: The Chemical Composition of Ultrafine Particles, Philos. T. Roy. Soc. A., 358, 2581–2592, 2000. Charron, A., Birmili, W., and Harrison, R. M.: Factors influencing new particle formation at the rural site, Harwell, UK, J. Geophys. Res., 112, D14210, doi:10.1029/2007JD008425, 2007. Cozic, J., Verheggen, B., Weingartner, E., Crosier, J., Bower, K., Flynn, M., Coe, H., Henning, S., Steinbacher, M., Collaud~Coen, M., Petzold, A., and Baltensperger, U.: Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch, Atmos. Chem. Phys., 8, 407–423, 2008. Dal Maso, M., Kulmala, M., Riipinen, I., Wagner, R., Hussein, T., Aalto, P.P., and Lehtinen, K. E. J.: Formation and growth of fresh atmospheric aerosols: eight years of aerosol size distribution data from SMEAR II, Hyytiala, Finland, Boreal Environ. Res., 10, 323–336, 2005. Hari, P. and Kulmala, M.: Station for Measuring Ecosystems–Atmosphere Relations (SMEAR II), Boreal Environ. Res. 10, 315–322, 2005. Harrison, R. M., Grenfell, J. L., Savagen, N., Allen, A., Clemitshaw, K. C., Penkett, S., Hewitt, C. N., and Davison, B.: Observations of new particle production in the atmosphere of a moderate polluted site in eastern England, J. Geophys. Res., 105, D14, 17 819–17 832, 2000. Hussein, T., Puustinen, A., Aalto, P. P., Mäkelä, J. M., Hämeri, K., and Kulmala, M.: Urban aerosol number size distributions, Atmos. Chem. Phys., 4, 391–411, 2004. Hussein, T., Dal Maso, M., Petaja, T., Koponen, I. K., Paatero, P., Aalto, P. P., Hämeri, K., and Kulmala, M.: Evaluation of an automatic algorithm for fitting the particle number size distributions, Boreal Environ. Res., 10, 337–355, 2005. Kannosto, J., Ristimäki, J., Virtanen, A., Keskinen, J., Aalto, P., and Kulmala, M.: Density analysis of boreal forest aerosols, Chemical Engineering Transactions, 10, 95–99, 2006. Keskinen, J., Marjamäki, M., Virtanen, A., Mäkelä, T., and Hillamo, R.: Electrical Calibration Method for Cascade Impactors, J. Aerosol Sci., 30, 111–116, 1999. Koponen, I., Virkkula, A., Hillamo, R., Kerminen, V.-M., and Kulmala, M.: Number size distributions and concentrations of the continental summer aerosols in Queen Maud Land, Antartica, J. Geophys. Res., 108, D18, 45872002, doi:10.1029/2003JD003614, 2003. Kulmala, M., Hämeri, K., Aalto, P. P., Mäkelä, J. M., Pirjola, L., Nilsson, E. D., Buzorius, G., Rannik, U., Dal Maso, M., Seidl, W., Hoffman, T., Janson, R., Hansson, H. C., Viisanen, Y., Laaksonen, A., and O'Dowd, C. D.: Overview of the international project on biogenic aerosol formation in the boreal forest (BIOFOR), Tellus, 53B, 324–343, 2001. Kulmala, M., Vehkamäki, H., Petäjä, T., Dal Maso, M., Lauri, A., Kerminen, V.-M., Birmili, W., and McMurry, P. H.: Formation and growth rates of ultrafine atmospheric particles: A review of observations, J. Aerosol Sci. 35, 143–176, 2004a. Kulmala, M., Laakso, L., Lehtinen, K. E. J., Riipinen, I., Dal Maso, M., Anttila, T., Kerminen, V.-M., Hõrrak, U., Vana, M., and Tammet, H.: Initial steps of aerosol growth, Atmos. Chem. Phys., 4, 2553–2560, 2004b. Kulmala, M., Lehtinen, K. E. J., and Laaksonen, A.: Cluster activation theory as an explanation of the linear dependence between formation rate of 3 nm particles and sulphuric acid concentration, Atmos. Chem. Phys., 6, 787–793, 2006. Laaksonen, A., Kulmala, M., O'Dowd, C. D., Joutsensaari, J., Vaattovaara, P., Mikkonen, S., Lehtinen, K. E. J., Sogacheva, L., Dal Maso, M., Aalto, P., Petäjä, T., Sogachev, A., JunYoon, Y., Lihavainen, H., Nilsson, D., Facchini, M. C., Cavalli, F., Fuzzi, S., Hoffmann, T., Arnold, F., Hanke, M., Sellegri, K., Umann, B., Junkermann, W., Coe, H., Allan, J. D., Rami Alfarra, M., Worsnop, D. R, Riekkola, M.-L., Hyötyläinen T., and Viisanen, Y.: The role of VOC oxidation products in continental new particle formation, Atmos. Chem. Phys., 8, 2657–2665, 2008. Lohman, U. and Feichter, J.: Global indirect aerosol effects: a review, Atmos. Chem. Phys., 5, 715–737, 2005. Maenhaut, W., Jaffrezo, J.-L., Hillamo, R. E., Mäkelä, T., and Kerminen, V.-M.: Size-fractionated aerosol composition during an intensive 1997 summer field campaign in northern Finland, Nucl. Instrum. Methods, B150, 345–349, 1999. Marjamaki, M., Keskinen, J., Chen., D. R., and Pui, D. Y. H.: Performance evaluation of the electrical low-pressure impactor (ELPI), J. Aerosol Sci., 31, 249–261, 2000. Marjamäki, M., Lemmetty, M., and Keskinen, J.: ELPI response and data reduction - I: Response functions, Aerosol Sci. Tech., 39, 575–582, 2005. McMurry, P., Wang, X., Park, K., and Ehara, K.: The relationship between mass and mobility for atmospheric particles: A new technique for measuring particle density, Aerosol Sci. Tech., 36, 227–238, 2002. Mäkelä, M., Aalto, P., Jokinen, V., Pohja, T., Nissinen, A., Palmroth, S., Markkanen, T., Seitsonen, K., Lihavainen, H., and Kulmala, M.: Observations of ultrafine aerosol particle formation and growth in boreal forest, Geophys. Res. Lett., 24, 1219–1222, 1997. Mäkelä, J. M., Hoffmann, T., Holzke, C., Väkevä, M., Suni, T., Mattila, T., Aalto, P. P., Tapper, U., Kauppinen, E. I., and O'Dowd, C. D.: Biogenic iodine emissions and identification of end products in coastal ultrafine particles during nucleation bursts, J. Geophys. Res., 107, 8110, doi:10.1029/2001JD000580, 2002. Mäkelä, J., Koponen, I., Aalto, P., and Kulmala, M.: One-year data of submicron size modes of tropospheric background aerosol in southern Finland, J. Aerosol Sci., 31, 595–611, 2001b. Mäkelä, J. M., Yli-Koivisto, S., Hiltunen, V., Seidl, W., Swietlicki, E., Teinilä, K., Sillanpää, M., Koponen, I. K., Paatero, J., Rosman, K., and Hämeri, K.: Chemical composition of aerosol during particle formation events in boreal forest, Tellus, 53B, 380–393, 2001a. O'Dowd, C. D., Aalto, P., Hämeri, K., Kulmala, M., and Hoffmann, T.: Atmospheric particles from organic Vapours, Nature, 416, 497–498, 2002. Pope, C. A. and Dockery, D. W.: Health Effects of Fine Particulate Air Pollution: Lines that Connect, J. Air Waste Manage. Assoc., 56, 709–742, 2006. Putaud, J.-P., Van Dingenen, R., Dell'Acqua, A., Raes, F., Matta, E., Decesari, S., Facchini, M. C., and Fuzzi, S.: Size-segregated aerosol mass closure and chemical composition in Monte Cimone (I) during MINATROC, Atmos. Chem. Phys., 4, 889–902, 2004. Ristimäki, J., Virtanen, A., Marjamäki, M., Rostedt, A., and Keskinen, J.: On-line measurement of size distribution and effective density of submicron aerosol particles, J. Aerosol Sci., 33, 1541–1557, 2002. Ristimäki, J.: Sampling and measurement methods for diesel exhaust aerosol, Tampere University of Technology Publications, 638, PhD Thesis, 2006. Saarikoski, S., Mäkelä, T., Hillamo, R., Aalto, P., Kerminen, V.-M., and, Kulmala, M.: Physico-chemical characterization and mass closure of size-segregated atmospheric aerosols in Hyytiälä, Finland, Boreal Environ. Res., 10, 385–400, 2005. Seinfeld, J. H. and Pandis, S. N.: Atmospheric chemistry and physics. From air pollution to climate change, John Wiley & Sons, 429–443, New York, 1998. Smith, J. N., Moore, K. F., Eisele, F. L., Voisin, D., Ghimire, A. K., Sakurai, H., and McMurry, P. H.: Chemical composition of atmospheric nanoparticles during nucleation events in Atlanta, J. Geophys. Res., 110, D22S03, doi:10.1029/2005JD005912, 2005. Tarvainen, V., Hakola, H., Hellen, H., Back, J., Hari, P., and Kulmala, M.: Temperature and light dependence of the VOC emissions of Scots pine, Atmos. Chem. Phys., 5, 989–998, 2005. Vaattovaara, P., Huttunen, P. E., Yoon, Y. J., Joutsensaari, J., Lehtinen, K. E. J., O'Dowd, C. D., and Laaksonen, A.: The composition of nucleation and Aitken modes particles during coastal nucleation events: evidence for marine secondary organic contribution, Atmos. Chem. Phys., 6, 4601–4616, 2006. Virtanen, A., Ristimäki, J., and Keskinen, J.: New method to define the effective density and fractal dimension of agglomerate particles, Aerosol Sci. Tech., 38, 437–446, 2004. Virtanen, A., Rönkkö, T., Kannosto, J., Ristimäki, J., Mäkelä, J. M., Keskinen, J., Pakkanen, T., Hillamo, R., Pirjola, L., and Hämeri, K.: Winter and summer time size distributions and densities of traffic related aerosol particles at a busy highway in Helsinki, Atmos. Chem. Phys., 6, 2411–2421, 2006. Wall, S. M., John, W., and Ondo, J. L.: Measurement of aerosol size distributions for nitrate and major ionic species, Atmos. Environ., 22, 1649–1656, 1988. Wehner, B. and Wiedensohler, A.: Long term measurement of submicrometer urban aerosols: statistical analysis for correlations with meteorological conditions and trace gases, Atmos. Chem. Phys., 3, 867–879, 2003. Wehner, B., Wiedensoler, A., Tuch, T. M, Wu, Z. J., Hu, M., Slanian, J., and Kiang, S. C.: Varability of the aerosol number size distribution in Beijing, China: New particle formation, dust storms, and high concentration backgrounds, Geophys. Res. Lett., 31, L22108, doi:10.1029/2004GL023827, 2005. Yu, H., Kaufman, Y J., Chin, M., Feingold, G., Remer, L. A., Anderson, T L., Balkanski, Y.,~Bellouin, N., Boucher, O., Christopher, S., DeCola, P., Kahn, R., Koch, D., Loeb, N., Reddy, M. S., Schulz, M., Takemura, T., and, Zhou M.: A review of measurement-based assessment of the aerosol direct radia-tive effect and forcing, Atmos. Chem. Phys., 6, 613–666, 2006. Zhang, O., Canagaratna, M. R., Jayne, J. T., Worsnop, D. R., and Jimenez, J.-L.: Time- and size-resolved chemical composition of submicron particles in Pittsburgh: Implications for aerosol sources and processes, J. Geophys. Res, 110, D07S09, doi:10.1029/2004JD004649, 2005. Zhang, Q., Stainer, C. O., Canagaratna, M. R., Jayne, J. T., Worsnop, D. R., Pandis, S. N., and Jimenez, J. L.: Insight into chemistry of new particle formation and growth events in Pittspurgh based on aerosol mass spectrometry, Environ. Sci. Tech., 38, 4797–4809, 2004a. Zhang, R., Suh, I., Zhao, J., Zhang, D., Fortner, E., Tie, X., Molina, L. T., and Molina, M. J.: Atmospheric new particle formation enhanced by organic acids, Science, 304, 1487–1490, 2004b.