Water‐soluble potassium, calcium, and magnesium in the aerosols over the tropical North Atlantic

Abstract

During July, August, and September of 1974, daily aerosol measurements were made at three station in the tropical North Atlantic: Sal Island, Cape Verde Islands; Barbados, West Indies; Miami, Florida. The two major components of the aerosols at each station were mineral aerosol, comprising Saharan dust, and sea salt. Fifty‐eight samples were analyzed to determine the atmospheric concentrations of water‐soluble sodium, potassium, magnesium, and calcium and of the mineral aerosol. By using a multiple variable regression technique, the dominant source of water‐soluble potassium was found to be sea salt; the Saharan dust did, however, contribute a significant and sometimes quite substantial fraction (up to 38%). The soluble magnesium was almost exclusively a consequence of the presence of sea salt aerosols. In contrast, the soluble calcium at Sal Island and Barbados was derived predominantly (∼80%) from the Saharan dust; at Miami the contribution from Saharan aerosols (∼50%) and locally generated soil aerosols (∼40%) dominated the sea salt aerosol with respect to the amount of soluble calcium contributed. In comparison to the global continent‐to‐ocean flux via streams, the flux of soluble potassium via the atmosphere is probably negligible; the flux of soluble calcium via the atmosphere, however, may be of the order of 10% of that via streams.