DETERMINING THE ACIDITY AND CHEMICAL-COMPOSITION OF FOG, HAZE AND CLOUD DROPLETS IN ISRAEL

The chemistry and acidity of individual droplets were analyzed in samp les of fog, haze and cloud collected at Tel Aviv University on the Med iterranean seacoast and at the top of Mt Meron and of Mt Carmel in nor thern Israel. Acidity was measured using pH paper in a cascade impacto r. The characteristics of droplets and interstitial particles 0.3-20.0 mum in size were identified using microspot and electron microscopy t echniques. The results revealed the following: (1) the aerosols in the micrometer and sub-micrometer range were mostly very acidic droplets, with pH as low as 2.0, caused by the presence of sulfuric acid; (2) l ower acidity was associated with an increase in droplet size, due to d ilution by condensation or nucleation scavenging of mineral dust, i.e. gypsum, calcite and dolomite; (3) both acidic and alkaline droplets c ontained significant amounts of sulfur; and (4) the alkaline droplets contained minerals and salt solutions of Na2SO4, CaSO4, or NaCl.