The role of dust storms in total atmospheric particle concentrations at two sites in the western U.S.

Abstract

Mineral aerosols are produced during the erosion of soils by wind and are a common source of particles (dust) in arid and semiarid regions. The size of these particles varies widely from less than 2 μm to larger particles that can exceed 50 μm in diameter. In this study, we present two continuous records of total suspended particle (TSP) concentrations at sites in Mesa Verde and Canyonlands National Parks in Colorado and Utah, USA, respectively, and compare those values to measurements of fine and coarse particle concentrations made from nearby samplers. Average annual concentrations of TSP at Mesa Verde were 90 μg m-3 in 2011 and at Canyonlands were 171 μg m -3 in 2009, 113 μg m-3 in 2010, and 134 μg m -3 in 2011. In comparison, annual concentrations of fine (diameter of 2.5 μm and below) and coarse (2.5-10 μm diameter) particles at these sites were below 10 μg m-3 in all years. The high concentrations of TSP appear to be the result of regional dust storms with elevated concentrations of particles greater than 10 μm in diameter. These conditions regularly occur from spring through fall with 2 week mean TSP periodically in excess of 200 μg m-3. Measurement of particles on filters indicates that the median particle size varies between approximately 10 μm in winter and 40 μm during the spring. These persistently elevated concentrations of large particles indicate that regional dust emission as dust storms and events are important determinants of air quality in this region. Key Points TSP concentrations are highly elevated at two sites in the western US mineral aerosols are dominated by particles larger than 10 u in diameter The spring/summer elevation of aerosols is related to dust storms ©2013. American Geophysical Union. All Rights Reserved.