Phosphorus associations in aerosols: What can they tell us about P bioavailability?

Phosphorus (P) in aerosols can originate from multiple sources (mineral dust, biomass burning, fuel emissions) and can be associated with multiple phases including various minerals, organic matter and P adsorbed on particle surfaces. These associations will greatly impact the solubility of P in an aerosol sample and thus determine the bioavailability of P from atmospheric deposition to oceanic ecosystems. Here we use a sequential leaching extraction to determine the distribution of P within different operationally defined fractions in aerosol samples reaching the Gulf of Aqaba from different air mass trajectories and at different seasons. We found that on average 40% of the P in aerosols is associated with the "authigenic" fraction (soluble in acetic acid) which is unlikely to dissolve in seawater and become bioavailable. Another 15% is associated with each the HCl-"detrital" and insoluble organic matter components that are also not readily bioavailable. Only 15-30% of P is associated with phases that are water soluble or that are relatively soluble oxide phases that may be bioavailable for organisms. We did not find a consistent relationship between the distribution of P in the various phases and air-mass back trajectory or season but a distinct and strong positive correlation was observed between metals associated with anthropogenic sources such as Zn and Ni and the extractable water soluble P fraction. This suggests that anthropogenic P sources are more soluble and bioavailable than mineral sources even though most of the Pin aerosols in this region is in the mineral phase. These results have implications for determining how changes in atmospheric input of P to the ocean related to urban development and anthropogenic (wood and fuel burning) activities may impact marine ecosystems. (C) 2009 Elsevier B.V. All rights reserved.