Atmospheric acidification of mineral aerosols: A source of bioavailable phosphorus for the oceans
Primary productivity of continental and marine ecosystems is often limited or co-limited by phosphorus. De-position of atmospheric aerosols provides the major external source of phosphorus to marine surface waters. However, only a fraction of deposited aerosol phosphorus is water sol-uble and available for uptake by phytoplankton. We propose that atmospheric acidification of aerosols is a prime mecha-nism producing soluble phosphorus from soil-derived miner-als. 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 col-lected over a 5-yr period at Finokalia, Crete. In addition, at least tenfold increase in soluble phosphorus was observed when Saharan soil and dust were acidified in laboratory ex-periments which simulate atmospheric conditions. Aerosol acidification links bioavailable phosphorus supply to anthro-pogenic and natural acidic gas emissions, and may be a key regulator of ocean biogeochemistry.