The fate of aerosol Fe in the surface water of the northwestern Pacific Ocean

The surface water of the northwestern Pacific Ocean, receiving huge amount of East Asian aerosols in winter and spring, provides an ideal platform to investigate the fate of aerosol Fe in the oceanic surface water. In this study, the variability through seasonal transformation for major Fe pools and processes, including aerosol deposition, dissolved and suspended Fe pools, and sinking particle fluxes, were investigated in the surface water of the northwestern Pacific Ocean during high and low aerosol deposition seasons from 2013 to 2014. The aerosol deposition flux in spring 2014 spring was about one order of magnitude higher than summer 2013, depositing 11 and 0.82 μmol total Fe m^-2 d^-1 for the high and low seasons, respectively. However, the dissolved Fe concentrations exhibit comparable low concentrations in the surface water between the two seasons. Instead, the Fe concentrations and the Fe/P ratios in suspended particles in the spring were 7 to 10 times higher than the summer. The particulate Fe/P and Al/P ratios are likely to reflect potential chemical processes from suspended to sinking particles. This study demonstrates that aerosol Fe is mainly adsorbed onto biotic suspended particles, indicating that food web would become the major pathway to transform the adsorbed Fe.