Chemical composition of aerosols collected over the tropical North Atlantic Ocean

Ambient aerosol samples were collected over the tropical northern Atlantic Ocean during the month of April 1996 onboard the R/V Seward Johnson. Dichotomous high-volume collector samples were analyzed for ferrous iron immediately after collection, while trace metals, anions, and cations were determined upon return to the laboratory. Data are analyzed with the aid of enrichment factor, principal component, and weighted multiple linear regression analyses. Average mineral aerosol concentrations amounted to 19.3±16.4 μg m^(−3) whereby the chemical characteristics and air mass back trajectories indicated the dust to be of a typical shale composition and Saharan origin. Calcite accounted for 3.0 and 7.9% of the mineral aerosol during the first and second halves of the cruise, respectively. Total iron concentrations (averaging 0.84±0.61 μg m^(−3)) are crustally derived, of which 0.51±0.56% is readily released as Fe(II). Eighty-six percent of this Fe(II) is present in the fine (