Parameterizing Residential Coal Emissions as a Source of Soluble Iron in an Earth System Model

HALEY E. PLAAS, Rui Li, Douglas Hamilton, Mingjin Tang, North Carolina State University

     Abstract Number: 509
     Working Group: Combustion

Abstract
Anthropogenic activities have altered the atmospheric burden and deposition fluxes of biogeochemically relevant trace metals, including iron (Fe). Fe content and solubility (i.e., bioavailability to primary producers) in combustion aerosol is modulated by the chemical properties of fuel-sources, as well as burn technologies applied between emission sectors. In this work, total and soluble Fe concentrations were measured in five distinct combustion aerosol types collected across China. Then, using the Mechanism of Intermediate complexity for Modeling Iron (MIMI), an atmospheric iron module embedded in the Community Earth System Model (CESM), we modified Fe solubility at its point of emission according to novel measurements. Modeled Fe deposition fluxes to key oceanic regions were assessed under pre-industrial (PI), present day (PD), and future (FU) anthropogenic emissions scenarios. By distinguishing residential from industrial coal burning in model simulations, we report a 3-fold increase in PD global soluble Fe fluxes stemming from anthropogenic sources (0.9 Tg yr-1 in the base simulation and 0.27 Tg yr-1 in the sensitivity case). Increases in soluble Fe deposition were most evident in the northeastern Pacific Ocean, in the Bay of Bengal, and across southeastern Asia. Model-observation comparisons suggest that model performance (ability to capture soluble Fe concentrations measured in aerosol at the Earth’s surface) was improved for these regions and for the South Atlantic. By the end of the century, model outputs suggest that soluble Fe deposition to marine systems could be decreased by 7 to 32 Gg yr-1, indicating more significant perturbations to biogeochemistry attributed to residential combustion not previously captured in Earth Systems Models. Our results highlight and quantify uncertainties related to trace metal delivery to ocean ecosystems in the Anthropocene.