Southern South American dust inputs to the South Atlantic and Southern Oceans: trace element solubility and deposition fluxes

Southern South America (SSA) is an important source of dust, and its associated micronutrient trace elements, to the waters of the Southern Ocean. As part of the UK contribution to the International GEOTRACES program, an aerosol sampling site (Carcass Island) was established in the western Falkland (Malvinas) Islands, downwind of dust sources in Patagonia. Samples were collected over two 7-month long periods and analyzed for soluble and total trace elements. Results indicated that dust was the dominant source of aerosol iron and manganese, elements with limiting or co-limiting roles for Southern Ocean primary productivity. Other micronutrient trace elements (e.g., copper and zinc) appeared to be more strongly affected by anthropogenic inputs, even in this sparsely populated region. Trace element fractional solubility at Carcass Island appears consistent with previous observations over the wider Atlantic Ocean. In the case of iron, a hyperbolic increase in solubility with decreasing atmospheric iron concentration was observed. This relationship has been suggested to indicate enhancement of solubility during atmospheric transport, but the very little available information on iron solubility in the region makes this difficult to verify. Soluble manganese to iron ratios in aerosols at Carcass Island suggest that deposition of SSA dust is unable to alleviate Mn deficiency in the waters of the Atlantic sector of the Southern Ocean.