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Atmospheric Research 54 2000 1–13 www.elsevier.comrlocateratmos
The size distribution of primary biological aerosol particles in cloud water on the mountain Kleiner
ž FeldbergrTaunus FRG
Sabine Matthias-Maser , Berit Bogs, Ruprecht Jaenicke
Institut fur Physik der Atmosphare, UniÕersitat Mainz, Becherweg 21, 55099 Mainz, Germany
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Received 29 March 1999; received in revised form 20 December 1999; accepted 26 February 2000
Abstract
During the field campaign, FELDEX 95 cloud water samples were collected and the insoluble particles were analysed by single particle analysis in order to determine the content of primary
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biological aerosol particles PBAP . It is found that 25 of the total insoluble particles are biological ones. During cloud events with increasing wind velocity, the concentration of biological
particles also increases. Anthropogenic influence leads to a higher amount of both total and biological particles. Within the size distribution, the percentage of biological particles decreases
with increasing radius. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Cloud water analysis; Insoluble component; Single particle analysis
1. Introduction
Aerosol particles have a great importance within the whole atmosphere. They have influence on the radiation budget, on the turbidity and range of sight, as well as on the
energy budget of the earth. Their important role in cloud physics as cloud condensation nuclei and as ice forming nuclei is known. These cloud development processes are
dependent on the size distribution and on the chemical composition of the aerosol particles. The atmospheric aerosol particles consist of mineral dust, sea salt, volcanic
dust, soot, particles, which are produced by chemical and physical reactions of trace
Corresponding author. Ž
. E-mail address: matthiasmail.uni-mainz.de S. Matthias-Maser .
0169-8095r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž
. PII: S 0 1 6 9 - 8 0 9 5 0 0 0 0 0 3 9 - 9
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gases, and of primary biological aerosol particles PBAP . They are ubiquitous and occur in all size classes.
PBAP in the atmosphere play an important role in air hygiene indoors as well as Ž
. outdoors. Viruses, bacteria, spores, pollen, and insect parts i.e., house dust mites cause
diseases or allergenic reactions in humans, animals and plants. Another aspect of the investigation of PBAP in the atmosphere is the role they play in
cloud physics. Atmospheric aerosol particles act as cloud nuclei. However, the majority of them need temperatures under y108C. The peculiarity of some PBAP is that they
have freezing capabilities even at temperatures of about y48C. That means that even if the surrounding is still supercooled, the cloud forming processes can be induced by these
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ice nucleation active PBAP. Schnell and Vali 1973
reported that a portion of atmospheric freezing nuclei was of biogenic origin. The sources of these nuclei include
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Ž decaying vegetation, marine plankton Schnell and Vali, 1976 and bacteria Maki et al.,
. Ž
. 1974 . Sun et al. 1993 discovered 17 species or varieties of three genera of ice
nucleation active bacteria on plants. Even dead bacteria may be active in producing Ž
. freezing nuclei Maki and Willoughby, 1978 .
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Ice nucleation activity INA of the free living fungus Fusarium was mentioned by Ž
. Pouleur et al. 1992 . They compared the INA of some species of Fusarium with the
INA of bacteria and lichens. The warmest temperatures at which ice nucleation occurs Ž
. for Fusarium aÕenaceum was y2.58C, which is close to that of lichen INA y28C and
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slightly lower than that of Pseudomonas y18C . As a result of their investigations, they found out that lichen INA and Fusarium INA could have a common origin. They
even suggested that ice nucleation of Fusarium acuminatum and F. aÕenaceum could Ž
. be the source of leaf derived nucleation LDN observed in decomposing leaf litter
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Schnell and Vali, 1973 . They suggested that the microflora is responsible for the decomposition of organic matter. F. acuminatum and F. aÕenaceum are both soilborne
fungi and are more prevalent in temperate and cold climates, where LDN concentration is highest.
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Investigations of Warren and Wolber 1991 show that a single gene is responsible Ž
. for the INA phenotype of the different microorganisms MO . This is better known for
bacteria than for ice nucleation in lichens. Ž
. Even pollen can contribute to condensation processes. Durham 1941 worked with
12 species of pollen to determine their response to air of various humidity levels. He found that all were hygroscopic in the sense that they acquired water from the vapor
below 100 relative humidity. The species studied include six weeds, two grasses and Ž
. four deciduous trees. Dingle 1966 mentioned the hygroscopicity of the protoplasm of
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ragweed ambrosia artimesiifolia at humidities higher than 51. There is no question about the fact that these particles are present in the atmosphere
and initiate ice nucleation or other condensation processes for cloud formation.
2. PBAP
A first attempt to examine PBAP in their entirety in the atmosphere was done by Ž
. Matthias-Maser and Jaenicke 1994 . They investigated the PBAP within the size range
y3
0.2 mm - r - 50 mm and found mean concentrations of PBAP N s 3.1 cm in
bio 3
y3
number and V s 6.5 mm cm
in volume. That amounts to a mean percentage of
bio
23.7 in number concentration and 22.3 in volume of the total aerosol particles. Calculating a mean density of PBAP of 1 g cm
y3
, the mass of PBAP comes to an amount of 6.5 mg m
y3
. The strong dependency of PBAP on the phenology and the annual variation of the
phenology could indicate an annual variation of PBAP. The great variability of N in
bio
spring as a consequence of the different florescence of the plants in combination with the different meteorological conditions could be seen allusively. Obviously, no charac-
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teristic annual variation of PBAP r 0.2 mm neither in number nor in volume was seen. The presumption that in winter the concentration of PBAP would decrease was not
Ž confirmed. The production mechanisms of PBAP in winter
reflotation, decaying .
processes are stronger than expected. Merely the composition of the PBAP changed within the year as follows. In spring: MO, pollen, some spores, a few fragments; in
summer: MO, pollen, spores, a few fragments; in autumn: MO, fragments, spores, a few pollen; and in winter: MO, fragments, spores, some pollen.
Because of their ability to act as ice nuclei and because they are thought to be insoluble, it is interesting to investigate their occurrence in cloudrfogwater. The
following paper is concerned with the determination of these particles in cloud water Ž
. Ž
. samples collected on the mountain ‘‘Kleiner Feldberg KFB rTaunus FRG ’’ about
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857 m above sea level Bogs, 1996 , in the course of the field campaign ‘‘FELDEX
Fig. 1. Time-scale of the cloud events during FELDEX 95.
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
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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
