The Fractional Solubility of Aluminium From Mineral Aerosols Collected in Hawaii and Implications for Atmospheric Deposition of Biogeochemically Important Trace Elements
Abstract
Understanding the systematics of the atmospheric deposition and dissolution of mineral dust in the surface ocean is of key importance to geochemistry and biogeochemistry. The atmospheric deposition route represents an important but poorly quantified part of the geochemical cycle as well as a vector for the delivery of biogeochemically important trace elements such as Fe to the surface ocean. The magnitude of this delivery process plays a vital role in biological processes as well as having consequences for the utilization of macro-nutrients and moderating atmospheric carbon dioxide levels. In order to further our understanding of this process we collected mineral aerosols from a 20m tower on the windward side of Oahu, Hawaii between February and May 2002, the high dust season. The fractional solubility of Al in the mineral aerosols ranged from 0.09 to 14.3% with a mean of 4.6%. Most of the dissolution took place within the first 24 hours of the suspension of these dusts in filtered surface seawater, but a further approx. 20% dissolved over an additional 3 day period. The fractional solubility of Al decreased with increased dust loading on the filter. However, the absolute amount of Al that dissolved from each filter correlated positively with the amount of non sea salt sulphate and nitrate on replicate filters. If confirmed, this result implies that the contribution of trace elements to surface waters is more likely regulated by the amount of acidity in the atmosphere rather than the amount of mineral aerosol. However, since much of the mineral dust that arrives in Hawaii has passed through air masses affected by intense industrialisation in Asia, the results we find may not be applicable to regions or periods that are not impacted by anthropogenic effects. Determining the underlying processes controlling, the solubility of mineral aerosols will require comparison of results from many different regions of the oceans. There are however no currently accepted methodologies for estimating this solubility which limits our ability to compare results from different research groups and different regions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMOS13F..06M
- Keywords:
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- 0312 Air/sea constituent fluxes (3339;
- 4504);
- 0330 Geochemical cycles (1030);
- 1615 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 4805;
- 4912);
- 4273 Physical and biogeochemical interactions