Residential burning is a significant source of soluble iron to the ocean

Understanding the physicochemical processes that supply atmospheric aerosol iron (Fe) to the ocean is crucial in our understanding of global biogeochemical cycles. Anthropogenic emissions contribute significant fluxes of aerosol Fe to the atmosphere, the soluble fraction of which can modulate marine primary productivity upon its deposition to the ocean surface. However, aerosol Fe solubility remains poorly constrained, due in part to a lack of direct measurements spanning a multitude of anthropogenic sources. We measured solubility of aerosol Fe from several distinct anthropogenic combustion processes and fuel types. The median Fe solubility varied widely by source, ranging from 0.03 % for power plant coal fly ash to 55.87 % for biofuel burning; furthermore, residential coal burning aerosol possessed much higher Fe solubility than industrial coal fly ash. Using new Fe solubilities reported herein, we updated parameters for anthropogenic aerosol Fe within the Mechanism of Intermediate complexity for Modeling Iron, an aerosol Fe module of the Community Earth System Model v2. Such updates led to significant improvement in model performance over ocean regions heavily influenced by anthropogenic emissions, and we identified residential burning as a significant source of soluble aerosol Fe to the ocean. Our work underscores the need to further refine understanding of physicochemical properties of aerosol Fe from a wide variety of anthropogenic sources. In turn, this understanding will aid in characterizing the influences of anthropogenic activities on past, present, and future atmospheric nutrient inputs to marine ecosystems.