Hygroscopic and CCN properties of aerosol particles in boreal forests

Article English OPEN
Hämeri, K. ; Väkevä, M. ; Aalto, P. P. ; Kulmala, M. ; Swietlicki, E. ; Zhou, J. ; Seidl, W. ; Becker, E. ; O'dowd, C. D. (2001)

The measurements of the hygroscopic and cloud condensation nuclei (CCN) properties of sub-micrometer atmospheric aerosol particles were performed with two tandem differential mobility analysers (TDMA) and a CCN counter at the Hyytiälä forest field station in south-central Finland during the BIOFOR campaign. The TDMAs were used to measure hygroscopic diameter growth factors of individual aerosol particles in the dry particle diameter range 10–365 nm when taken from the dry state (relative humidity RH <5%) to RH=90%. The CCN counter was used to study the activation of aerosol particles when exposed to supersaturated conditions. The measurements show clear diurnal pattern of particle solubility. The pattern was strongest for particles in nucleation and Aitken modes. The lowest growth factor (soluble fraction) values were detected during late evening and early morning and the maximum was observed during noon-afternoon. The highest soluble fractions were determined for nucleation mode particles. The response of hygroscopic growth to changes of relative humidity suggests that the soluble compounds are either fully soluble or deliquescent well before 70% RH. The hygroscopic growth was investigated additionally by a detailed model using the size-resolved composition from the impactor samples. The comparison between different instruments shows good consistency. We found good agreement for the 20 nm growth factors measured with two TDMAs, not only on average but also regarding the temporal variation. The similar conclusion was drawn for comparison of TDMA with CCNC for Aitken mode particles with dry sizes 50 and 73 nm. Differences between wet and dry spectra measured using APS and CSASP spectrometer probes were used to derive growth factors for coarse mode particles. Growth factors for coarse mode particles (Dp ca. 2 μm) ranged between 1.0 and 1.6. Agreement between the evolution of growth factors with time for both accumulation and coarse modes was observed regularly. However, similar portions of the data set also indicated clear differences and consequently different chemical compositions between both modes. When the differences between both modes were observed, the coarse mode always behaved in a less hygroscopic manner, with growth factors near one.DOI: 10.1034/j.1600-0889.2001.530404.x
  • References (50)
    50 references, page 1 of 5

    Aalto, P., Kulmala, M. and Nilsson, E. D. 1995. Nucleation events on the Va¨rri o¨ environmental measurement station. J. Aerosol Sci. 26S, 411-412.

    Aalto, P. and Kulmala, M. 2000. Using a cloud condensation nuclei counter to study CCN properties and concentrations. Boreal Environment Research 5, 349-359.

    Aalto, P., Ha¨meri, K., Becker, E., Weber, R., Salm, J., Ma¨kela¨, J., Hoell, C., O'Dowd, C., Karlsson, H., Hansson, H.-C., Va¨keva¨, M., Koponen, I. and Kulmala, M. 2001. Physical characterization of aerosol particles during nucleation events. T ellus 53B, 344-358.

    Bigg, E. K. 1986. Discrepancy between observation and prediction of concentrations of cloud condensation nuclei. Atmos. Res. 20, 82-86.

    Covert, D. S., Gras, J. L., Wiedensohler, A. and Stratmann, F. 1998. Comparison of directly measured CCN with CCN modeled from the number-size distribution in the marine boundary layer during ACE 1 at Cape Grim, Tasmania. J. Geophys. Res. 103, 16,597-16,608.

    Dick, W. D., Saxena, P. and McMurry, P. H. 2000. Estimation of water uptake by organic compounds in submicron aerosols measured during the Southeastern Aerosol and Visibility Study. J. Geophys. Res. 105, 1471-1479.

    Gerber, H. 1988. Relative humidity parameterization of the lognormal size distribution of ambient aerosols. In: L ecture notes in physics 309 (Eds. Paul E. Wagner and Gabor Vali). Springer Verlag, Berlin, pp. 237-238.

    Ha¨meri, K., Kulmala, M., Aalto, P., Leszynski, K., Visuri, R. and Ha¨mekoski, K. 1996. The investigations of aerosol particle formation in urban background area of Helsinki. Atmos. Res. 41, 281-298.

    Ha¨meri, K., Charlson, R. J., Hansson, H.-C. and Jacobson, M. 1998. Hygroscopic properties of ammonium sulfate aerosol particles mixed with slightly soluble organic compound. J. Aerosol Sci. 29S, 587-588.

    Ha¨meri K., Va¨keva¨ M., Hansson H.-C. and Laaksonen A. 2000. Hygroscopic growth of ultrafine ammonium sulphate aerosol measured using an ultrafine tandem diVerential mobility analyser. J. Geophys. Res. 105, 22,231-22,242.

  • Metrics
    No metrics available
Share - Bookmark