Modification of Saharan dust size distribution during its transport over the Anatolian Plateau

Abstract

Particle number size distribution in dust plumes and its modification as the plume travels over the Anatolia were investigated by measuring particle number size distributions at two stations: one located on the Mediterranean coast of Turkey and the other on the Anatolian plateau. Clustering of backtrajectories revealed six trajectory clusters at the Marmaris station and nine clusters at the Ankara station. Cluster 6 in Marmaris and clusters 6, 7 and 9 in Ankara stations had the potential to transport Saharan dust to stations. Concentration of particles with D ≤ 1 μm increased during dust events in the Ankara station, but decreased at the Marmaris station. Higher PM1 concentrations during the non-dust period at the Marmaris station were attributed to the dominance of secondary particle formation on PM1 concentrations. Occurrence of sea salt episodes at the Marmaris station and anthropogenic episodes at the Ankara station affects the distribution of episodes. If different types of episodes are not differentiated and all episodes are considered as dust, it can lead to misleadingly high dust episodes in winter. Six Saharan dust episodes were sequentially intercepted first at the Marmaris and then at the Ankara stations. These episodes were used to study how dust size distribution is modified as the plume travels from the Mediterranean coast to central Anatolia. On the average, travel time between the two stations is 1–2 days. Particle number concentrations in 1 μm ≤ D ≤ 110 μm size range were consistently high at the Ankara station, indicating that local sources play a role in modifying the number size distribution as the plume travels over the Anatolian plateau.