Anthropogenic iron oxide aerosols enhance atmospheric heating

Abstract

Combustion-induced carbonaceous aerosols, particularly black carbon (BC) and brown carbon (BrC), have been largely considered as the only significant anthropogenic contributors to shortwave atmospheric heating. Natural iron oxide (FeO _x) has been recognized as an important contributor, but the potential contribution of anthropogenic FeO _x is unknown. In this study, we quantify the abundance of FeO _x over East Asia through aircraft measurements using a modified single-particle soot photometer. The majority of airborne FeO _x particles in the continental outflows are of anthropogenic origin in the form of aggregated magnetite nanoparticles. The shortwave absorbing powers ( P _abs) attributable to FeO _x and to BC are calculated on the basis of their size-resolved mass concentrations and the mean P _abs(FeO _x)/ P _abs(BC) ratio in the continental outflows is estimated to be at least 4–7%. We demonstrate that in addition to carbonaceous aerosols the aggregate of magnetite nanoparticles is a significant anthropogenic contributor to shortwave atmospheric heating.

Abstract

Iron oxide nanoparticles contribute to shortwave absorption in the form of desert dust. Moteki et al. show that iron oxide particles of anthropogenic origin, potentially from motor vehicles and blast furnaces, also contribute to atmospheric heating over East Asia.