Ž .
for volume V , V . The result is a first estimate of the insoluble unspecific biological
tot bio
content of the atmospheric aerosol particles in cloud water.
4. Results
Fig. 1 illustrates the time scale of the experiment, the hatched fields show the time period of the cloud events, the marked areas inside show the time from which the
analysed samples originate.
Fig. 3. Size distributions of insoluble particles in cloud water on KFB referred to milliliter of cloud water Ž
. 7r8r11 .
We chose three events for presenting the results. The cloud water of these events Ž
. originate from droplets larger than 2.5 mm in radius ICPS or round-jet impactor . The
liquid water content during the discussed time periods was always about 400 mgrm
3
, so in most cases, the measurements took place in local cumulus clouds as a result of forced
convection. Unfortunately, there were no direct parallel drop spectra available. The first started on the 1st of Nov. and lasted about 30 h. We analysed two samples,
one from the beginning and the other from the middle of the event. Fig. 2 shows the size
Fig. 4. Size distributions of insoluble particles in cloud water on KFB referred to milliliter of cloud water Ž
. 13r11 .
Ž .
distributions d nrdlog r of the total number of insoluble particles small symbols and of Ž
. Ž
. Ž
biological particles big symbols from 0700–0800 h cross and 1900–2200 h up .
Ž .
triangle referred to milliliter of cloud water and their corresponding percentage dotted in each size class. You see that the concentration increased with time. This is mainly
Ž caused by spores see the relative maximum in the percentage curve with about 40 in
. Ž
. the 3rd radius interval and plant debris with up to 90 in the 8th and 9th interval .
Even the number of MO increased. Looking at the meteorological conditions during that event, we had an increase of wind velocity producing strong defoliation, which could
explain the growing concentration of bacteria and of plant debris.
The second event we analysed was on the 7th and 8th of Nov. and lasted about 27 h Ž
. and we analysed samples of the first 7r11, 1720–1800 h and of the second half
Ž .
8r11, 0700–0800 h . The results are seen in Fig. 3. Prior to this event, we had a dry, Ž
. cold T - 08C period with strong defoliation. This is seen in the concentration of the
Ž . Ž
. giant particles 7r11
see percentage curve , where we first of all found plant debris and pollen, which were deposited on the leafs and got resuspended into the atmosphere
through this defoliation. Later, within the cloud event, the temperature increased while Ž
. Ž
. the wind velocity decreased 1 mrs . We found now 8r11 more MO and less plant
debris and pollen. Looking at both events, the percentages of PBAP per milliliter cloud water increased
from 17–25 up to 40–41 during one event. Ž
. In the next cloud event we will consider, it started on the 13th of Nov. see Fig. 1
and lasted 39 h. Fig. 4 shows the size distributions of two samples collected in the Ž
. Ž
. middle
2100–2400 h and at the end
14r11, 1100–1400 h of this event. The
concentrations of the total particles were one order of magnitude larger and even the concentration of PBAP was twice of that compared to the previous events. The whole
Ž .
sampling period was largely influenced by the Rhine-Main region southern winds , which leads to this increase of the total, as well as of the biological particles, first of all
Ž .
MO. This effect anthropogenic influence leads to an increase of MO was found also in Ž
. the ground based measurements Matthias-Maser and Jaenicke, 1995 . However, the
percentages did not change during the whole event.
5. Comparison with other size distributions of PBAP
