Contribution of Desert Dust Transport to Air Quality Degradation of Urban Environments Recent Model Developments

Mineral dust, produced by wind erosion over arid and semi-arid areas of North Africa, may transport away to the Middle East, Mediterranean, Europe, even into and across the Atlantic Ocean (Kallos et al., 2002). This material transported away from its origin is considered as an important climate and environment modifier. Dust particles by absorbing and backscattering both the incoming solar radiation and the infrared outgoing radiation modify the Earth’s radiation budget (Andreae, 1996). In addition, they alter the cloud microphysics processes acting as cloud condensation nuclei and having pH < 7.0 play a role in neutralization of the acid rains (Hedin and Likens, 1996). Also with the long-range dust transport, important nutrients are transported from their sources to other regions and may significantly modify the biogeochemistry of these marine and terrestrial ecosystems (Swap et al., 1996). For example, the deposition of the North African dust material on the Mediterranean Sea provides important nutrients, such as nitrogen species, phosphorus and iron, which may enhance the marine productivity. Some summer algal blooms in the Mediterranean Sea may be explained by such Saharan dust deposition (Dulac et al., 1996). Guerzoni et al. (1999) have estimated the amount of the atmospheric dust mass deposited on Mediterranean region to be ∼40×106 tons. Even though, they turned out to this magnitude by measured atmospheric mass flux at 9 coastal sites (which is considered as a small number of sites for such a work), this is considered as a valuable estimation since it is the only one found so far.