The size distribution of primary biological aerosol particles in rain-water

Abstract

This chapter demonstrates the relevance of biological aerosol particles as active participants in cloud forming processes. It uses an existing method for the determination of atmospheric biological aerosol particles to investigate rain-water samples and this size distribution in rainwater. Primary biological aerosol particles (PBAP) describe airborne solid particles that are derived from living organisms, including microorganisms and fragments of all varieties of living things. This definition includes a wide spectrum of biological particles spread over a large size range. The larger particle range includes bacteria, algae, spores of lichen, mosses, ferns, and fungi, pollen, plant debris like leaf litter, parts of insects, human, and animal epithelial cells. They are a ubiquitous component of the atmospheric aerosol and come to about 24% of the concentration of the total atmospheric particles. Besides their effects on air hygiene, they play an important role in cloud physics. Schnell and Vali suggested that a portion of atmospheric freezing nuclei was of biogenic origin. The sources of these nuclei include decaying vegetation, marine plankton, and bacteria. The peculiarity of the bacteria is that they have a freezing capability even at temperatures about -4° C while most mineral particles need temperatures below -10° C.