干旱区生态环境知识资源中心

Rainwater was collected in ultra-clean conditions during three field experiments (two on Corsica and one during a North-South Atlantic transect of the 1988 Polarstern cruise). This rainwater was immediately filtered and the major ions were measured by ionic chromatography, atomic absorption and colorimetric methods. In these marine areas, the concentrations of major ions range over one or two orders of magnitude and are generally dominated by the redissolution in rainwater of the sea salts. The non-sea salt component shows the presence of anthropogenic nitric and sulfuric acids which are well correlated with the origin of the air masses and which lead to acidic rains (pH from 4 to 5). High values of pH (6-7) are also observed and can be explained by the neutralization of strong acids by natural alkaline dusts as calcite, which are mainly transported from the desert areas of the African continent. A study of these variations in major ion compositions in relation to three-dimensional, air-mass trajectories demonstrates the behaviour of these two components during African dust transport.