Acid rain on Mt Carmel, Israel

Wetfall and bulkfall were collected on Mt Carmel, Israel, for three hydrological years, 1989–1992, using an acid precipitation sampler equipped with a moving cover. The analysis of 40 rain events indicated that in more than 65% of the events the pH was acid (<5–6) and in nearly 40% of the events strongly acid. Only in 12% of the events was the pH distinctly alkaline. Bulkfall collected on the same site had a higher pH, due to much higher Ca²⁺ and K⁺ concentrations, suggesting the effects of local aerosols emanating from calcareous soils. The relatively high Na⁺ and Cl⁻ levels and their Na⁺/Cl⁻ ratio of 0.866 indicated the marine origin of the major portion of dissolved salts. Alkaline wetfall, strongly enriched in K⁺, Cl⁻ and Na⁺, was associated with duststorms. X-ray and chemical analysis of the dryfall (dust) showed the presence of quartz, carbonates, clay minerals, feldspar, halite and gypsum. SO₄²⁻, responsible for the acidity of the wetfall, appears to be imported from Central or Eastern Europe, via the Mediterranean Sea, as suggested by back-trajectories of 26 rain events.