Impact of a Dust Event on the Size Distribution of Metal Elements in Atmospheric Aerosols at a Coastal Region and over the Ocean

Abstract

Size-segregated aerosol samples were collected in the Qingdao coastal region and over the East Sea and the Pacific Northwest from March to April in 2016, and the concentration of metal elements (Al, Na, Fe, Mg, K, Cu, Pb, and Cd) were analyzed. The characteristics and the variation in the size distribution of the metal elements in the samples during dusty weather were discussed, as well as the sources and factors that influence the metals. The results indicated that the concentration of Al, Fe, K, Na, Cu, and Pb in the aerosols in the Qingdao coastal samples increased significantly by 85%-1400%, while the concentration of Cd decreased by 8%; the concentrations of Al, Fe, K, Cu, Pb, and Cd in the samples over the ocean increased by 163%-4580%, while the concentration of Na decreased by 62% during dusty weather. In addition, the size distribution of K changed from a double-peak to a coarse peak mode; that of Pb and Cd changed from a fine peak mode to a double-peak distribution. Cu still presented a double-peak distribution in which the proportion of coarse particles increased; Al, Fe, Mg, and Na showed little variation in their size distribution with a single peak in coarse mode. The dust event had different effects on the size distributions of the metal elements in the coastal and marine aerosol samples. The size distribution of the metal elements (Al, Fe, Mg, Na, and K) in the aerosols collected at the Qingdao coastal site had one peak of 2.1-3.3 μm during dusty weather; the peak moved to 3.3-4.7 μm for marine samples. In addition, the proportion of Al, Fe, Mg, Na, K, Pb, and Cd in the coarse mode decreased by 1%-35% for dust aerosol samples collected in Qingdao coastal region, whereas the proportion of these metals in coarse mode increased by 4%-33% for samples collected over the East Sea. This difference may be related to the hygroscopic growth, transport path, and height of the dust.