Abstract
Ground-based observation at a large distance from desert regions suggested the possibility of long-range transport of bioaerosols along with desert dust. To understand the transport process, observation of bioaerosols associated with dust particles over KOSA (Asian dust) source areas is essential. In this paper, we introduce the observations of bioaerosols, which had been recently carried out at a desert site, Dunhuang in northwest China, using a tethered balloon. The tethered balloon served to lift instruments from the ground to about 1,200 m. Bioaerosol samples were collected at an altitude of 800 m above the ground. Particulate matters in the samples were analyzed individually with a fluorescent microscope and a scanning electron microscope equipped with an energy dispersive X-ray analyzer (SEM-EDX). According to the fluorescence microscopic observation with DAPI solution which stains DNA in samples, approximately 10 % of water-insoluble particles at 800 m showed strong fluorescent signals under UV irradiation, indicating the presence of microorganisms. The SEM-EDX analysis revealed that most of the fluorescent particles stained by DAPI were attached on mineral particles, indicating the significance of mineral dust as a carrier of microorganisms. In addition, these results show that coupling tethered-balloon observation with individual particle analysis is an effective approach to study the diffusion of mineral particles with bioaerosols in the boundary layer.
