95.’’ The direct surroundings of the ‘‘KFB’’ is covered with forest of some deciduous trees and conifers. In the north, we found some rural regions, and in the south, the
Rhine-Main-region is situated. During a time period of 2 weeks from 1st until 15th of November, different meteorological conditions caused the top of the mountain to be
Ž .
shrouded in clouds Fig. 1 . Within these cloud events, several cloud water samples were taken and analysed. The measurements took place in autumn where, first of all, plant
debris and MO were expected to be in the atmosphere. Additionally, it gave us the opportunity to investigate how far the decaying processes influence the concentration of
these PBAP in clouds.
3. Methods
For cloud water sampling, three different samplers were used: the rotating arm Ž
. Ž
collector RAC sampling, all waterdrops with radius 7.5 mm Kramer and Schutz,
¨ ¨
. Ž
. Ž .
1994 , an isokinetic cloud probing system ICPS Maser and Jaeschke, 1993 and a
Ž .
round-jet impactor Enderle and Jaeschke, 1991 , the latter both with cut-off radii of 2.5 mm. After sampling, the cloud water was frozen until analysis in the laboratory.
The evaluation of the water samples was performed after Matthias-Maser and Ž
. Ž
. Jaenicke 1994 and Gruber 1995 . It was divided into two parts: for the particles larger
than 2 mm a light microscope was used and the particles with r - 2 mm were evaluated Ž
. in a scanning electron microscope SEM equipped with an energy dispersive X-ray
Ž .
detector EDX . Therefore, two different preparations were necessary. For the particles with 0.2 mm - r - 2 mm up to 10 ml of the thawed cloud water was filtered through a
Ž .
polycarbonate filter Fa. Millipore with poresize of 0.2 mm. Afterwards, the filter was dried for 2 h at 308C. For investigation in the SEM, the filter had to be sputtered with
carbon to produce a conductive surface on the filter. In the SEM, the biological particles Ž
were characterized according to three criteria: striking morphology special forms like .
Ž spheres, rods, characteristic forms, etc. , elemental composition P, S, K, Ca sometimes
. Ž
with Cl on a high background spectrum , and behaviour during EDX sometimes
. instable due to electron beam, shrinking .
For the analysis of the giant aerosol, particles up to 20 ml of cloud water was filtered Ž
. through a cellulose nitrate filter Fa. Satorius with a poresize of 3 mm. The filters were
then placed on glass slides and also dried for about 1 h at 308C. The identification of PBAP was performed using an unselective protein dye, which reacts with the carboxyl
Ž .
group of a protein Jaenicke and Matthias, 1988 . As a result, the protein-containing particles, i.e., pollen, plant debris, epithelial cells, and even spores, which are difficult to
stain got a bluish colour, which characterizes them as biological. The staining solution, 0.05 ml, was put into the cloud water before filtration, and after a penetration time of
7–10 days under dark and cold storage, the fogwater was filtered as described before.
All samples were evaluated in nine size classes and the number concentration Ž
d Nrdlog r for total, biological and non-biological particles which is the difference .
between the total and the biological particles d Nrdlog r y d Nrdlog r was calcu-
tot bio
lated taking into consideration the particle radius, referred to milliliter of cloud water and to cubic centimeter of air of which the waterdroplets originate. Error calculations
including poisson error and errors of the instrument and sampling conditions lead to less than 10. In order not to complicate the graphs, they were omitted. We determined the
percentage of the biological particles to the total aerosol particles for each size class, which gives more information of the different components of PBAP, and then we
Ž
y1 y3
calculated the total number concentration N
and N in ml
and cm , respec-
tot bio
. Ž
3 y1
y3
tively and the total volume concentration V and V
in mm ml
and cm ,
tot bio
. Ž
. respectively . We also calculated the mean concentrations for number N , N
, and
tot bio
Fig. 2. Size distributions of insoluble particles in cloud water on KFB referred to milliliter of cloud water Ž
. 1r11 .
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
