Influence of Saharan dust on the rain acidity and atmospheric input to the Mediterranean

Abstract

It has long been recognized that Saharan dust may be transported a long way from its sources, particularly over the ocean1, and especially over the tropical North Atlantic, as far as the Caribbean2–7, and over various areas of the Mediterranean8–10. The eolian transport of desertic aerosols is a major contribution to oceanic sedimentation11–13 and may have important climatic implications14. This phenomenon is responsible for episodes of so-called ‘red rain’ or ‘red snow’ which have been identified in various areas of the European continent15–17. Numerous red rains and red dust falls have been observed in Corsica. From 1984 data on the chemistry of precipitation collected in South Corsica, we show here that due to its CaCO3 content, Saharan dust significantly increases the pH of rain water. This may counteract the effects of acidic rain. An assessment of African dust deposition indicates that, compared with the sediments discharged by the Rhone river, atmospheric input to the northwestern Mediterranean contributes significantly to sedimentation in that region.