HYGROSCOPIC GROWTH OF AEROSOL-PARTICLES IN THE PO VALLEY

SVENNINGSSON, IB; HANSSON, HC; WIEDENSOHLER, A; OGREN, JA; NOONE, KJ; HALLBERG, A
1992 | Tellus B Chem Phys Meteorol | 44 (5) (556-569)

A Tandem Differential Mobility Analyser (TDMA) was used to study the hygroscopic growth of individual ambient aerosol particles in the Po Valley, Italy. The measurements were made during the GCE fog experiment in November 1989. During fog, the interstitial aerosol (D(p)(at ambient relative humidity) < 5 mum) was sampled. Two modes of particles with different hygroscopic growth were found for 0.030 mum < D(p)(dry) < 0.20 mum. On average, the fraction of particles in the two modes were almost equal. The mean growth factor at 85% r.h. was 1.44 +/- 0.14 for the more-hygroscopic mode and 1. 1 +/- 0.07 for the less-hygroscopic mode. The growth factors and the proportion of the particles that were less hygroscopic varied considerably from day to day, but no significant size dependence was seen. Comparison of growth factors for pure salt particles and the measured growth factors indicates that both hygroscopic modes contain a major insoluble part. The effect of the external mixing of hygroscopic properties on the activation of particles to fog droplets is discussed and the fraction of particles that were activated as a function of particle size is predicted. Comparison with the measured scavenging fraction as a function of particle size shows that the hygroscopic properties of the individual particle are as important as the particle size in determining if it will be activated in a fog.

A STATISTICAL EXAMINATION OF THE CHEMICAL DIFFERENCES BETWEEN INTERSTITIAL AND SCAVENGED AEROSOL

NOONE, KJ; OGREN, JA; HALLBERG, A; HANSSON, HC; WIEDENSOHLER, A; SWIETLICKI, E
1992 | Tellus B Chem Phys Meteorol | 44 (5) (581-592)

The difference in chemistry between interstitial aerosol particles and particles that were scavenged into fog droplets is examined using multivariate statistical techniques. 15 trace elements (P, S, Cl, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, Pb, EC) were used in the analysis. There was a significant difference in composition between the two types of particles. S, Fe, Mn, and Cu were among the elements best describing the scavenged aerosol, while the interstitial aerosol was best described by elemental carbon (EC).

CALIBRATION OF THE TSI 3760 CONDENSATION NUCLEUS COUNTER FOR NONSTANDARD OPERATING-CONDITIONS

1990 | Aerosol Sci Technol | 13 (4) (478-485)

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