DISCOSAT · Determining the Impact of Seawater Chemistry on the Solubility of Atmospheric Trace metals

Bioactive trace metal (TM) distributions in the ocean impact directly on the growth and sustainability of micro-organisms and on the marine biogeochemical cycles of bulk elements that sustain life, such as carbon, nitrogen, phosphorus and sulphur. A primary delivery mechanism of TMs to the modern surface ocean is via atmospheric transport and deposition in aerosols and precipitation. An important linkage between the deposition of TMs and their impact on the biology of the upper ocean, lies in the proportion of TMs in aerosols that dissolve and becomes available to biota. Critical physico-chemical variables in seawater have the potential to affect TM dissolution (i.e. temperature, pH, dissolved oxygen and metal binding ligands) and there is a requirement to investigate their effects to better constrain global biogeochemical models. These physico-chemical variables are known to vary considerably between different geographically regions in the current upper ocean. Furthermore, their spatial variability is predicted to be substantially altered in the next few centuries due to global change. The DISCOSAT (Determining the Impact of Seawater Chemistry On the Solubility of Atmospheric Trace metals) project will test the extent to which changes to the physico-chemical composition of surface seawater (within environmentally relevant ranges) have a significant impact on the dissolution of TMs from aerosols. The project will use a range of representative North Atlantic subtropical and temperate aerosol and seawater samples and incorporate state of the art analytical and aerosol TM processing techniques to simulate dissolution processes.