Ph.D Thesis

Ph.D StudentSchlesinger Pnina
SubjectIdentification and Characterization of Airborne Biological
Particles during Dust Storm Events in Israel
DepartmentDepartment of Agricultural Engineering
Supervisors PROFESSOR EMERITUS Yaacov Mamane


Israel is subjected every year to dust storms that originate in the Saharan desert, and the Arabian deserts, mainly during winter and spring. The physical and chemical nature of dust storms is fully documented. However less attention was paid to their microbial content. The current research examined the relation between dust events and quantitative and qualitative aspects of the airborne bacterial and fungal populations in Israel. The hypothesis of the research was that the concentrations of airborne microorganisms are higher during dust events then on adjacent clear days.

Dust events in 2004-2005 were sampled. Samples were taken before or after, and during the dust storms. Dust particles were collected with a dichotomous sampler, and analyzed by X-ray fluorescence. Airborne microorganisms were collected with the Six Stage Andersen Viable Impactor. During the dust events, the concentrations of atmospheric particles increased 7-20 fold, compared to levels of 50 mg/m3 in adjacent clear days. often anthropogenic pollutants increased during dust events. Concentrations of airborne bacteria were 9 times higher during dust events, whereas airborne fungi concentrations were 1.5 to 7.3 times higher. The airborne bacteria and fungi were less then 7 mm, thus they may penetrate the respiratory tract, and may lead to health problems. The species were also affected by the occurrence of dust events. The concentrations of fungi like Alternaria alternata, Cladosporium cladosporioides and Penicillium chrysogenum were one order of magnitude higher during dust events then during clear days. Other fungi, like Chaetomium strumarium, Chaetomium succineum and Emericella nidulans, were observed only during dust events, whereas the concentrations of the Basidiomycota were not influenced considerably by the occurrence of dust events. Some of the fungi that their concentrations increased during dust events are known as pathogenic and allergenic to human beings, or as causing infections in animals, or damage to agricultural crops or produce. Cluster analysis has revealed that most of the fungi are not directly associated with particle content, except the Basidiomycota that were clustered together with specific chemical elements. During the two years of the study 28 species of teleomorphic Ascomycota, 171 species of anamorphic Ascomycota, three species of Zygomycota, yeasts and fungi of the phylum Basidiomycota were collected.

It was shown that dust events from the Sahara and other deserts have a significant effect on airborne microbial populations in Israel, which might lead to serious health, agricultural, and ecological implications.