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Abstract: Atmospheric concentrations of trace metals over the oceans are investigated through analysis of aerosol samples collected during cruises from the UK to the Falkland Islands and from South Africa to Australia. The readily soluble concentrations of Cu (4–256pmolm−3), Ni (0.1–54pmolm−3), Ba (0.2–60pmolm−3), Zn (6–316pmolm−3), Cd (0.01–0.29pmolm−3) and Pb (0.4–22pmolm−3) were measured in the aerosols, along with total concentrations of crustal elements (Fe, Al and Mn) to evaluate the crustal contributions. Air mass back trajectories suggested most of the aerosol samples had spent several days over the ocean prior to collection. The highest metal concentrations were observed in aerosols close to South Africa, Australia and major cities in South America, although these concentrations were lower than had been reported previously in the literature. Apart from Ba, which had a major crustal source, the trace metals were enriched relative to crustal sources in most samples, including some collected thousands of kilometers from emission sources. The mean trace metal concentrations in the remote Indian Ocean were lower than those measured in the Atlantic Ocean. Even lower concentrations are reported in the literature for the remote Pacific Ocean. In contrast to previous studies, no clear north–south gradient is observed in the concentrations of the trace metals in the aerosols. Lead isotope measurements were also carried out on aerosol samples using a multicollector inductively coupled plasma mass spectrometer to assist in source apportionment. Clear differences were noted in the isotope ratios collected on either side of the Indian Ocean with Australian lead ore dominating over much of the eastern and mid-southern Indian Ocean. Samples collected over the western Indian Ocean and Atlantic Ocean under South African influence had lead isotopes quite different from those seen in South African cities in the past, and are closer in ratio to the coal signature of the region. [Copyright &y& Elsevier]

Recent studies have highlighted the impact of sea surface iodide concentrations on the deposition of ozone to the sea surface and the sea to air flux of reactive iodine. The use of models to predict this flux demands accurate, spatially distributed sea surface iodide concentrations, but to date, the observational data required to support this is sparse and mostly arises from independent studies conducted on small geographical and temporal scales. We have compiled the available measurements of sea surface iodide to produce a data set spanning latitudes from 69°S to 66°N, which reveals a coherent, large scale distribution pattern, with highest concentrations observed in tropical waters. Relationships between iodide concentration and more readily available parameters (chlorophyll, nitrate, sea surface temperature, salinity, mixed layer depth) are evaluated as tools to predict iodide concentration. Of the variables tested, sea surface temperature is the strongest predictor of iodide concentration. Nitrate was also strongly inversely associated with iodide concentration, but chlorophyll-a was not.