Abundances and Microphysical Properties of Light‐Absorbing Iron Oxide and Black Carbon Aerosols Over East Asia and the Arctic. Issue 15 (2nd August 2020) - Yoshida, Atsushi
Abstract: Black carbon (BC), brown carbon, and light‐absorbing iron oxides (FeO x ) aerosols affect Earth's energy budget through their strong absorption of solar radiation. FeO x aerosols can also affect global biogeochemical cycles through their role as a nutrient for oceanic phytoplankton. However, observational data for these aerosols required for evaluating their effects using global models are scarce, especially for FeO x . Here, we summarize and compare the data sets of BC and FeO x from five ground‐based and three aircraft observation campaigns conducted in the East Asian and Arctic regions during the 2009–2018 period acquired using a modified single‐particle soot photometer. In these campaigns, >80% of FeO x ‐containing aerosols in the 170–270 nm FeO x core size range had microphysical features indicating an anthropogenic origin. The particle size distribution for each of the BC and FeO x was similar in all of the data sets except for those dominated by fresh urban pollution or pristine Arctic air. The campaign‐averaged mass concentrations of FeO x and BC were ~60–360 ng/m 3 and ~240–1, 300 ng/m 3, respectively, in East Asia, and ~6 ng/m 3 and ~20–30 ng/m 3, respectively, in the Arctic. The campaign‐averaged FeO x /BC mass concentration ratio varied within a narrow range of 0.2–0.6 in both East Asian and Arctic regions. In every campaign, FeO x, BC, and carbon monoxide were tightly correlated with each other with similar slope to the urban campaigns (around Tokyo), implying the spatiotemporal variation of anthropogenic FeO x emission around northern middle‐to‐high latitudes is similar to those of anthropogenic BC and CO emissions. Key Points: Mass concentrations of anthropogenic iron oxide (FeO x ) were at least 20% of those of black carbon (BC) in both East Asia and the Arctic FeO x, BC, and carbon monoxide were tightly correlated with each other in both East Asia and the Arctic Particle size distributions of both FeO x and BC were presented and compared in detail