| Summary: | Atmospheric deposition of trace metals to the oceans is investigated in this study with analysis of aerosol samples collected during cruises from the UK to the Falklands and from South Africa to Australia. The readily soluble concentrations of Cu, Ni, Ba, Zn, Cd and Pb were measured in the aerosols, along with crustal elements and major ions to evaluate the sea spray and 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 above both crustal and sea salt sources in most samples including some collected 1000s of km 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. The dry deposition rates calculated from the aerosol data were similar for the North and South Atlantic and South Indian Oceans reflecting the increase in industrialisation and atmospheric emissions in the southern hemisphere. Lead isotope ratios were measured in the aerosols with Multi Collector- Inductively Coupled Plasma - Mass Spectrometry. These results showed real differences in the isotopic ratios of aerosols collected in different marine regions and enabled the source of remote samples to be tentatively identified. Copper complexation was investigated in rain samples collected in Norwich, UK, and during the cruises. Humic material was also investigated as a potential organic ligand. The complexation was measured with Chelex resin, Sep-Pak columns and Adsorptive Cathodic Stripping Voltammetry with tropolone as a competing ligand. Strong organic complexation was observed in semi-urban and marine rain samples with conditional stability constants between 10" and 1014. Model solutions of copper and humic matter found organic complexes of a similar strength to those observed in the rain samples suggesting humic material as a potential source. A large proportion of the copper in the rains was associated with strong organic complexes over the pH range 4-8 in both filtered and unfiltered rain samples suggesting complexation is an important process both in the atmosphere and on arrival to oceans.
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