Color-related differences in the chemical composition of aerosol-laden filters

We examined color-related differences in the chemical composition of simila r to 6000 aerosol filters collected from 1989 to 1997 at three sampling sit es in the North Atlantic Ocean (Barbados, Bermuda, and Izana) operated for the Atmosphere/Ocean Chemistry Experiment (AEROCE). The concentrations of t he trace elements (AI, Br, Ca, Cl, Fe, Na, Sb, Sc, Se, V) and two ions, NO3 - and SO42-; the activities of Pb-210 and Be-7; and the mixing ratios of oz one were compared and contrasted for groups of samples and data matched to the three basic colors of aerosol filters (brown, gray or white). Chemical composition is related to filter color, that is, the brown and gray samples correspond to mineral dust and absorbing aerosol from various pollution so urces, respectively, although these substances often are mixed in varying p roportions. The white filters are best regarded as indicating the absence o r low concentrations of dust or other absorbing aerosols, and they are ofte n indicative of clean marine air. Relationships among atmospheric substance s differ significantly in the color-stratified data subsets, and grouping t he samples by color provides unique insight into the relationships among mi neral dust, pollution aerosol, and other substances over the North Atlantic . (C) 2001 Elsevier Science Ltd. All rights reserved.