The concentration of airborne soil dust at Enewetak Atoll(11 degrees N, 162 degrees E) in April 1979 was 2.3 micrograms per cubic meter but decreased steadily to 0.02 microgram per cubic meter over the next 5 months. The spring dust is probably derived from China; its deposition rate ( approximately 0.3 millimeter per 1000 years) suggests that it may be a significant contributor to the deep-sea sediments of the North Pacific.

The concentrations of trace elements in precipitation and dry deposition are presented for samples collected at Enewetak Atoll (11°N, 162° E) during SEAREX experiments in 1979. The concentrations of Al, Sc, Mn, Fe, Co, and Th in rain are dominated by crustal material, and for these elements, wet deposition evidently exceeds dry deposition. For most of these elements the present rates of atmospheric deposition at Enewetak are similar to their mean rate of accumulation in sediments over the past 5–10,000 years, suggesting that the air‐to‐sea exchange of particles is closely tied to the sedimentary cycle of the mid‐Pacific. Noncrustal sources govern the concentrations of Pb, Zn, Cu, Se, and Cd in wet and dry deposition samples. Analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples, and even though these estimates do not necessarily reflect the dry deposition to the ocean surface, the results suggest that recycled sea spray often amounts to more than 50% of the total dry deposition of the enriched elements. Recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements. The net deposition rates of elements such as Cu and Zn are greater than or equal to their inputs from vertical mixing, but the net deposition of Pb clearly exceeds the input from upwelling. The current net deposition rates of the enriched elements are also similar to their rates of removal to sediments. These results indicate that air‐sea exchange processes may significantly affect the chemistry of trace metals in the open ocean.

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.

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Cascade impactor and bulk filter samples of atmospheric sea salt were collected at wind speeds from 3.4 to 10 m/s at coastal tower sites in the Florida Keys and Enewetak Atoll as part of the SEAREX (Sea Air Exchange) Program. Simultaneous dry deposition measurements were made to polyethylene plates. The samples were analyzed for Na as an indicator of sea salt. If the observed atmospheric sea salt particle mass distributions are corrected for the reduced collection efficiency of large particles, the observed dry deposition rates agree well with rates estimated from atmospheric sea salt particle concentrations and theoretical particle deposition velocities derived from gravitational settling velocities or from the equations of Slinn and Slinn (1980, 1981) for deposition to smooth, solid surfaces as well as natural water surfaces. The results emphasize the fact that even though large particles may represent only a small fraction of the total mass of sea salt over the ocean, they can dominate the dry deposition rates of the sea salt aerosol.