Variations on morphology and elemental composition of mineral dust particles from local, regional, and long‐range transport meteorological scenarios

Abstract

[1] Mineral dust is the second major source of PM 10 in Madrid, reaching up to 80% of the PM 10 mass during certain long-range dust transport events. Three different types of scenarios have been found to be associated with the high particle concentration episodes in the city: local anthropogenic, regional recirculation, and African dust transport processes. The present study focuses on the characterization of the individual mineral dust particles related to some chemical and morphological features during these three types of episodes, with special attention to local and regional episodes. To achieve this purpose, four different samples were selectively collected during the 2004-2005 period campaigns, one corresponding to each type of scenario and other sample from an Atlantic ventilated one. Meteorological situation, dust source identification, impact on ambient concentrations, size range distribution, and particle individual analysis have been characterized for each of them. Elemental composition and morphology of more than 30,000 mineral particles were analyzed by computer-controlled scanning electron microscopy. Particles were grouped into clusters based on their elemental composition, and the aspect ratio (AR) of each cluster or category was compared for each type of episode. The AR was related to the mineralogical crystal structure of each chemical cluster. The dates chosen for microscopy analysis were in good agreement in size distribution and chemical composition with the average of the dates in the entire campaign and with those from previous campaigns. Major differences between local/regional and long-range transported mineral dust were found in the relative abundance between carbonates and silicates, with much higher abundance of calcium carbonates in the first ones. These differences between silicate and carbonate contents were consistent with the results found in previous campaigns and were directly related to the composition of the parent topsoil by studying the Ca/Si ratios of similar episodes recorded all over the Iberian Peninsula. Differences in morphology were also found for these scenarios. The predominance of calcium carbonate under regional and local influence is scientifically relevant since this mineral is known to react with both SO 2 and HNO 3 in the atmosphere. Larger average AR values were found for dust particles from long-range transport, and smaller average AR values were found for particles from local and regional resuspended dust. The increasing average AR value has been linked to the silicate cluster presence, whereas a reduction has been observed within the carbonate cluster.Citation: Coz, E., F. J. Gómez-Moreno, G. S. Casuccio, and B. Artíñano (2010), Variations on morphology and elemental composition of mineral dust particles from local, regional, and long-range transport meteorological scenarios,

Chemical Modification of Dust Particles during Different Dust Storm Episodes

“…6 indicates that these dust particles still have great potential to further absorb the acidic materials in the downstream air. Dust particles heterogeneous uptake of SO 2 to their surfaces can change SO 2 distribution in the atmosphere Usher et al, 2003;Li and Shao, 2009a;Coz et al, 2010). The anthropogenic sulfate forcing is estimated to decrease because of the reduced load of externally mixed sulfate aerosols (Bauer and Koch, 2005).…”

“…1 are consistent with our meteorological observations at the sampling site. The meteorological scenarios can cause different dust episodes (i.e., regional, local, and global) (Coz et al, 2010). Circles on the trajectories mark the D1 (blue), D2 (black), D3 (red), respectively, and they indicate the 6-hour interval.…”

“…The dust particles containing calcium exhibit extensive reactivity with SO 2 and NO 2 or nitric acid and sulfur acid (Li and Shao, 2009a;Coz et al, 2010). The mixing degree of Ca in the dust particle directly affects chemical reactions with acidic gases or acids in the air (Usher et al, 2003).…”

Sources of PM<sub>2.5</sub> carbonaceous aerosol in Riyadh, Saudi Arabia

“…A third possibility was that the Ca is crustal in origin but from a different source region than most of the other sampled dust. Ca enrichment ) 4 M a y 2 0 1 2 2 0 M a y 2 0 1 2 2 3 M a y 2 0 1 2 2 5 M a y 2 0 1 2 2 7 M a y 2 0 1 2 3 1 M a y 2 0 1 2 4 J u n 2 0 1 2 6 J u n 2 0 1 2 1 0 J u n 2 0 1 2 1 2 J u n 2 0 1 2 1 4 J u n 2 0 1 2 1 6 J u n 2 0 1 2 1 8 J u n 2 0 1 2 2 0 J u n 2 0 1 2 2 2 J u n 2 0 1 2 2 4 J u n 2 0 1 2 2 6 J u n 2 0 1 2 3 0 J u n 2 0 1 2 2 J u l 2 0 1 2 4 J u l 2 0 1 2 6 J u l 2 0 1 2 8 J u l 2 0 1 2 1 0 J u l 2 0 1 2 1 2 J u l 2 0 1 2 1 4 J u l 2 0 1 2 1 6 J u l 2 0 1 2 1 8 J u 2 0 1 2 3 1 A u g 2 0 1 2 2 S e p 2 0 1 2 4 S e p 2 0 1 2 6 S e p 2 0 1 2 8 S e p 2 0 1 2 2 2 S e p 2 0 1 2 2 4 S e p 2 0 1 2 2 6 S e p 2 0 1 2 in dusts may vary across the Middle East region (Coz et al, 2010), and thus the correlation between Ca and other crustal species could diverge depending upon the dust source region. Regardless of dust source region, during transport to Riyadh, as ambient SOC precursors were oxidized, the products may have partitioned to particle surfaces, resulting in simultaneous transport of Ca and OC.…”

Dual-wavelength light-scattering technique for selective detection of volcanic ash particles in the presence of water droplets

“…However, dust particles are often non-spherical (e.g. Coz et al, 2010) and, therefore, their light-scattering properties can differ from the values that are calculated using the Mie theory. Curtis et al (2008) studied the light-scattering properties of many representative dust aerosol components and found that a significant deviation between Mie theory calculation and measurement exists.…”