Eolian Dust Collected in Springtime (1979 and 1984 Years) at the Seawater-Air Interface of the Northern Red Sea

Abstract

Atmospheric dust samples have been collected over the Red Sea during springtime in 1979 and in 1983 by mesh sampling and by high-volume filters. Mineralogical-, grain-size-, chemical-and biological analyses have been performed to give a first sedimentological picture of the dust present in the lower atmosphere of this area. The meteorology during both sampling periods was characterized by indirect transport of materials by prevailing northwesterly wind. In this conditions mass concentration values are subordinate to those measured during a moderate episode of direct transport. The grain-size distribution and the clay mineralogy of the dust are controlled by the variable atmospheric dynamics occurred during the two samplings. In particular, a higher wind energy (MR 79 Cruise) is responsible for the transport far away of the finest smectites. Conversely, atmospheric dust collected in dependence on average lower energy level (MR 83 Cruise) is richer in smectite than the former one. Besides factors such as meteorology and energy level, also the land morphology plays an important role for the control of the dust mineralogy (f.i. the “barrier action” due to a chain transverse to the wind flow, and the effect due to the break off of the same chain). The elemental compositions of both insoluble and soluble fractions of the particulate are controlled by the prevailing northwesterly wind. The pollen grains loading decreases with the latitude and testifies a dominant long-range transport of pollen species.