Aerosol composition of urban and desert origin in the Eastern Mediterranean. I

Aerosol samples were collected in Tel-Aviv, Israel, during two different atmospheric situations, clear days and dust storms, and were analyzed for shape, size distribution, elemental composition, and presence of sulfate in individual particles. Results of two cases are presented in this paper. In both cases about 80% of the 0.2 to 2.0 µm particles contained sulfate. On the clear day over 50% of the total were pure sulfates while 27% were mixed sulfates; on the dusty day 63% were mixed sulfates — desert particles coated with sulfate — and only 20% were pure sulfates. The sulfate content of the desert particles was fairly high, on the order of 0.1 g sulfate g^?1 of desert particles. A possible explanation of this phenomenon may be heterogeneous nucleation of SO₂ on the surfaces of insoluble desert particles during their passage over the Mediterranean.