Atmospheric bioaerosols transported via dust storms in the western United States

Measurements are presented showing the presence of biological material within frequent dust storms in the western United States. Previous work has indicated that biological particles were enhancing the impact of dust storms on the formation of clouds. This paper presents multiple case studies, between April and May 2010, showing the presence of and quantifying the amount of biological material via an Ultraviolet Aerodynamic Particle Sizer during dust events. All dust storms originated in the Four Corners region in the western Untied States and were measured at Storm Peak Laboratory, a high elevation facility in northwestern Colorado. From an Aerodynamic Particle Sizer, the mean dust particle size during these events was approximately 1 m, with number concentrations between 6 cm^-3 and 12 cm^-3. Approximately 0.2% of these dust particles had fluorescence signatures, indicating the presence of biological material.