Abundance and Emission Flux of the Anthropogenic Iron Oxide Aerosols From the East Asian Continental Outflow

Anthropogenic iron oxide (FeOx) aerosols can affect atmospheric radiation, marine biogeochemistry, and human health. However, due to lack of observational data, their atmospheric abundance and emission flux are not well understood. In this study, we observed size-resolved concentrations of FeOx (170-2100 nm) and black carbon (BC, 70-850 nm) aerosols at a remote site in the East China Sea in March 2016 using a modified single-particle soot photometer (SP2). Light signals measured by the SP2 and particle morphology and compositions analyzed by a transmission electron microscope revealed that most of the observed FeOx aerosols are of anthropogenic origin. Clear correlations were found between mass concentrations of FeOx and BC (R-2 = 0.717) and between FeOx and carbon monoxide (CO) (R-2 = 0.718) in air masses from China, indicating that their emission sources are spatially similar. The correlation slopes of mass concentration (ng/m(3)) are similar to 0.3 and 0.0015, respectively. Based on the correlation slopes and emission inventories of BC and CO in China, we estimated emission flux of anthropogenic FeOx aerosols from China to be 0.21-0.49 FeTg/yr. Based on the observed size distribution and previous studies on mass fraction of FeOx and non-FeOx, we also estimated emission flux of anthropogenic Fe (FeOx + non-FeOx) in PM10 as 0.74-1.7 FeTg/yr. These emission fluxes from China are comparable to global emission fluxes in currently reported inventories of anthropogenic Fe (0.51-1.91 FeTg/yr). Our results suggest that the current emission inventories of anthropogenic Fe are underestimated.