Mineralogical and Chemical Composition of Dry Atmospheric Deposition on Jeddah City, Eastern Coast of the Red Sea

Atmospheric dust contains harmful minute-sized minerals that may cause a remarkable environment effect on marine life. The city of Jeddah expands drastically since the seventies and the dust content of harmful minerals increases. In this study fifty-two dust samples were collected at four locations using vertical dust trappers. Dust samples were analyzed for the major elements Al, Fe, Ca and Mg and the trace elements Mn, Cu, Zn, Cr, Ni, Pb and Cd. Some selected samples were analyzed for grain size distribution and mineralogical composition. Particles of the falling dust were mainly silty-sized and particle diameter increases in the direction of the prevailing wind indicating local mobilization. The mineralogical composition was dominated by quartz, plagioclase feldspars, calcite and gypsum. These minerals are widely present in the rock outcrops in the vicinity of the city. Results of major and trace elements show that trace elements particularly Cu and Zn were enriched in the dust particles relative to the continental crust. Applying factor analysis permitted the distinction of two dust populations, one originating from the crustal denudation and the other is constituted from anthropogenic particles. Mixing of the two components at varying degrees explains the variability of the chemical composition of the dust material.