A Mineralogy‐Based Anthropogenic Combustion‐Iron Emission Inventory

Abstract

Atmospheric supply of iron can modulate ocean biogeochemistry, due to its key role in global nitrogen and carbon cycles. Current estimates predict up to 20% of global ocean net primary productivity depends on an atmospheric iron source. Using a technology‐based methodology, we revise total and soluble anthropogenic iron emissions and resolve iron into its mineral components, which allows modeling mineral‐specific atmospheric reactions. We compare different methodologies for representing anthropogenic iron solubility: measured in mild and strong leaches and estimated using a mineralogy basis and identify the emissions that are most affected by such assumptions. The inclusion of metal smelting as an iron source increases iron emissions by up to 10 times higher in the fine aerosol fraction (smaller than 1 μm) than most previous inventories. Different solubility assumptions alter anthropogenic soluble iron emissions and deposition by a factor of 20 and 10, respectively. Using solubilities measured in mild leaches and calculated by mineralogy give 20–30 Gg/yr anthropogenic emissions and 40–50 Gg/yr deposition, while those measured in strong leaches give 80–440 Gg/yr emissions and 200–450 Gg/yr deposition. This range of anthropogenic soluble iron deposition leads to global soluble iron deposition of 1,900–2,300 Gg/yr when dust, wildfires, and atmospheric processing are included, indicating such assumptions can affect global soluble iron supply by about 30%. In regions where marine primary productivity is iron limited, anthropogenic combustion‐iron contributes up to half of the atmospheric soluble iron flux to the North Pacific Ocean but supplies less than 5% to the Southern Ocean.

Recent (1980 to 2015) Trends and Variability in Daily‐to‐Interannual Soluble Iron Deposition from Dust, Fire, and Anthropogenic Sources

“…We compare trends and variability in three major sources of soluble iron (dust, fire, and anthropogenic combustion), using three versions of the model to test for robustness. A new transient (1980 to 2015) monthly anthropogenic iron (defined as sum of smelting iron and fuel combustion of coal, oil, and wood) emission inventory, based on Rathod et al (2020), is developed and presented here for the first time.…”

Iron from coal combustion particles dissolves much faster than mineral dust under simulated atmospheric acid conditions

“…To improve the accuracy of our simulations of Fe-containing aerosols, we revised the on-line Fe dissolution schemes in the original model (Ito et al, 2021a) in conjunction with the mineralogy-based emission rates and a more dynamic range of pH estimates. To implement 3-step dissolution schemes, we used the mineral-specific emission inventory for anthropogenic Fe emissions (Rathod et al, 2020). To apply the Fe dissolution schemes for high ionic strength in aerosols, we used the mean activity coefficient for pH estimate (Pye et al, 2020).…”

“…Mineral dust has low Fe solubility (dissolved Fe/ total Fe) near the source regions, generally below 0.5% (e.g., Schroth et al, 2009;Shi et al, 2011c), increasing somewhat as a result of atmospheric processing (e.g., Baker et al, 2021;Baker et al, 2020). Other sources of bioavailable Fe to the ocean are from combustion sources such as biomass burning, coal combustion and oil combustion (e.g., shipping emissions) (e.g., Ito et al, 2018;Rathod et al, 2020). Although these sources are only a small fraction of the total Fe in atmospheric particulates, the Fe solubility of pyrogenic sources can be 1-2 orders of magnitude higher than in mineral dust, and thus can be important in promoting carbon uptake.…”

“…Wang et al (2015) estimated that coal combustion produces around ~0.9 Tg yr -1 of atmospheric Fe (on average for , contributing up to ~86% of the total anthropogenic Fe emissions. A more recent study, which has included metal smelting as atmospheric Fe source, estimated that coal combustion emitted ~0.7 Tg yr -1 of Fe for the year 2010, contributing around 34% of the total anthropogenic Fe (Rathod et al, 2020). Although the use of coal as a principle energy source has been recently reduced as a result of concern about air quality and global warming, coal is still an important energy source in a number of countries in particular in the Asia-Pacific region (BP, 2020).…”

Supplementary material to "Iron from coal combustion particles dissolves much faster than mineral dust under simulated atmospheric acid conditions"

“…The proton + oxalate dissolution scheme (Table 1) was applied in Test 1 and 3, while proton-promoted dissolution is used for Test 2. We adopted the mineral-specific inventory for anthropogenic Fe emissions (Rathod et al, 2020) in Test 1 and 2. In Test 3, the Fe speciation of Krakow ash was used for all combustion sources.…”