Abstract
In a forested near-urban location in central Germany, the
CCN efficiency of particles smaller than 100 nm decreases
significantly during periods of new particle formation. This
results in an increase of average activation diameters, ranging
from 5 to 8% at supersaturations of 0.33% and 0.74%,
respectively. At the same time, the organic mass fraction in
the sub-100-nm size range increases from approximately 2/3
to 3/4. This provides evidence that secondary organic aerosol
(SOA) components are involved in the growth of new
particles to larger sizes, and that the reduced CCN efficiency
of small particles is caused by the low hygroscopicity of
the condensing material. The observed dependence of
particle hygroscopicity (k) on chemical composition can
be parameterized as a function of organic and inorganic
mass fractions (forg, finorg) determined by aerosol mass
spectrometry: k = korg forg + kinorg finorg. The obtained value
of korg ~ 0.1 is characteristic for SOA, and kinorg ~ 0.7 is
consistent with the observed mix of ammonium, sulfate
and nitrate ions.
CCN efficiency of particles smaller than 100 nm decreases
significantly during periods of new particle formation. This
results in an increase of average activation diameters, ranging
from 5 to 8% at supersaturations of 0.33% and 0.74%,
respectively. At the same time, the organic mass fraction in
the sub-100-nm size range increases from approximately 2/3
to 3/4. This provides evidence that secondary organic aerosol
(SOA) components are involved in the growth of new
particles to larger sizes, and that the reduced CCN efficiency
of small particles is caused by the low hygroscopicity of
the condensing material. The observed dependence of
particle hygroscopicity (k) on chemical composition can
be parameterized as a function of organic and inorganic
mass fractions (forg, finorg) determined by aerosol mass
spectrometry: k = korg forg + kinorg finorg. The obtained value
of korg ~ 0.1 is characteristic for SOA, and kinorg ~ 0.7 is
consistent with the observed mix of ammonium, sulfate
and nitrate ions.
| Original language | English |
|---|---|
| Journal | Geophysical Research Letters |
| Volume | 37 |
| DOIs | |
| Publication status | Published - 2010 |
Bibliographical note
The information about affiliations in this record was updated in December 2015.The record was previously connected to the following departments: Nuclear Physics (Faculty of Technology) (011013007)
Subject classification (UKÄ)
- Subatomic Physics