European atmospheric pollution imported by cooler air masses to the Eastern Mediterranean during the summer.

In this study we combine Pb isotopes, Pb, Ni, Cu, Zn, and several major metal concentrations, identification of the aerosol particles, and synoptic and back trajectory analyses to obtain direct evidence for the extent and nature of mixing between Middle Eastern and European sources emissions of metals and aerosols. During the summer months aerosols collected in Israel are highly polluted by metals (EF(Ni) = 120, EF(Cu) = 320, EF(Zn) = 30, EF(Pb) = 540; average values). The fraction of European Pb of mostly industrial sources is 61 +/- 21% in Jerusalem, and the fraction of European Cu, Zn, Ni, and aerosols should be on the same order. Whenever a steep pressure gradient is built between the barometric trough originating from the Persian Gulf and the subtropical ridge along the African coast, stronger westerly winds and cooler temperatures (deep Persian Trough) prevail overthe Middle East, and higher amounts of European pollution are observed in the atmosphere (74 +/- 13%). On the other hand, when the Persian Trough is in its shallow mode, the proportion of European pollution is lower (45 +/- 18%, based on Pb isotopes). This study demonstrates that atmospheric pollution over the East Mediterranean region during the summer is influenced not only by local atmospheric dispersion conditions but also by the ability of the atmosphere to inherit a significant proportion of pollutants from European sources.