Atmospheric acidification of mineral aerosols: a source of bioavailable phosphorus for the oceans
1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
2School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
3Institute of Chemical Engineering and High Temperature Chemical Processes, Foundation for Research and Technology Hellas, Patras, Greece
4School of Earth and Environment, University of Leeds, Leeds, UK
5Department of Chemistry, University of Crete, Heraklion, Crete, Greece
6Israel Oceanographic Limnological Research, Tel Shikmona, Haifa, Israel
Abstract. Primary productivity of continental and marine ecosystems is often limited or co-limited by phosphorus. Deposition of atmospheric aerosols provides the major external source of phosphorus to surface waters. However, only a fraction of deposited aerosol phosphorus is water soluble and available for uptake by phytoplankton. We propose that atmospheric acidification of aerosols is a prime mechanism producing soluble phosphorus from soil-derived minerals. Acid mobilization is expected to be pronounced where polluted and dust-laden air masses mix. Our hypothesis is supported by the soluble compositions and reconstructed pH values for atmospheric particulate matter samples collected over a 5-year period at Finokalia, Crete. At least tenfold increase in soluble phosphorus is observed when Saharan soil and dust were acidified in laboratory experiments which simulate atmospheric conditions. Aerosol acidification links bioavailable phosphorus supply to anthropogenic and natural acidic gas emissions, and may be a key regulator of ocean biogeochemistry.