Dissolution of manganese from marine atmospheric participates into seawater and rainwater

Abstract

A significant fraction of the Mn in a marine aerosol of Saharan origin was found to come into solution on contact with an artificial rainwater and also a natural coastal seawater, on a time scale of a few minutes. The fraction of the non-lattice Mn released on contact with the rainwater increased with decreasing pH from 29% at pH 5.1 to 85% at pH 2 (equivalent to 20% to 59% of the total Mn), whilst in coastal seawater, 36% (25% of the total Mn) came into solution. This behaviour is consistent with the environmental and limited experimental data available. The release of dissolved labile forms of Mn, and probably other metals, through such dissoluton reactions is potentially an important step in the geochemical cycles of these elements. The carbonate content of the aerosol appears to provide a neutralizing effect which modifies the release of Mn when the aerosol was added to a mildly acidic rainwater.