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

Abstract. Understanding the physicochemical processes that supply atmospheric aerosol iron (Fe) to the ocean is crucial for understanding of global biogeochemical cycles. Anthropogenic activity contributes 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, anthropogenic 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 power plant coal fly ash. Using the new Fe solubilities reported herein, we updated parameters for anthropogenic aerosol Fe within the Community Earth System Model. Anthropogenic combustion is estimated to contribute up to 20 % of the global soluble Fe flux to the ocean in the present day. Furthermore, we identified residential coal burning as a previously neglected but potentially important source with regional flux contributions ranging from < 1 % to 21 %. Our work underscores the need to further refine understanding of aerosol Fe properties from a wide variety of anthropogenic sources by increasing observations in more novel aerosol regimes, with a focus on residential coal burning. This understanding will in turn aid in characterizing the influences of anthropogenic activity on past, present, and future atmospheric nutrient inputs to marine ecosystems.