Atmospheric trace elements at Enewetak Atoll: 1. Concentrations, sources, and temporal variability

The concentrations of 29 elements were measured in aerosol particles collected in 1979 during SEAREX experiments at Enewetak Atoll (11°N, 162°E) in the tropical North Pacific. The concentrations of Na, Mg, Cl, K, Ca, and Br were dominated by marine sources; these elements had similar mass‐size distributions, and their atmospheric concentration ratios (normalized to Na) were similar to the corresponding ratios in bulk seawater. Atmospheric inputs of aluminosilicate particles from crustal weathering controlled the aerosol particle concentrations of Al, Sc, Mn, Fe, Co, Cs, Ba, Ce, Eu, Hf, Ta, and Th. Mean concentrations of these crustally derived elements decreased by an average of 91% (±4.1%) from the local dry season (April to May) to the wet season (July to August); this general decrease was attributed to the abatement of dust storms in Asia. At times the influx of dust from Asia dominated the concentrations of V, Cr, Rb, and Cu in aerosol particles, but when dust concentrations decreased, noncrustal sources for these elements became apparent. A fourth group of elements (Zn, Se, Ag, Cd, Sb, I, and Pb) exhibited average, atmospheric concentrations that were higher than those expected from the flux of sea salt or the dispersal of mineral aerosol particles. Enrichments of these trace elements relative to average crustal material increased as the atmospheric dust concentrations subsided. Supplement is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document C83‐001; $2.50. Payment must accompany order.