Atmospheric Iron Research Articles

Slowly Rotating Peculiar Star BD00°1659 as a Benchmark for Stratification Studies in Ap/Bp Stars

We present the results of a self-consistent analysis of the magnetic silicon star BD+00°1659, based on its high-resolution spectra taken from the ESPaDOnS archive (R = 68,000). This narrow-lined star shows the typical high Si abundance and Si ii– iii anomaly, making it an ideal prototype for investigating the vertical distribution of Si and Fe in the stellar atmosphere. The derived abundances, ranging from helium to lanthanides, confirm the star’s classification as a silicon Bp spectral type. Silicon and iron are represented by lines of different ionisation stages (Fe i– iii, Si i– iii), indicating an ionisation imbalance interpreted as evidence of atmospheric stratification. Our stratification analysis reveals that there is a jump in iron and silicon abundances of 1.5 dex at atmospheric layers with an optical depth of logτ5000 = −0.85–−1.00. Non-LTE calculations for iron in this stratified atmosphere show minor non-LTE effects. Our results can be applied to studying the impact of stratification on the emergent flux in rapidly rotating Si stars with similar atmospheric parameters and abundance anomalies (for example, MX TrA), where direct stratification analysis is challenging due to line blending.

Source and fate of atmospheric iron supplied to the subarctic North Pacific traced by stable iron isotope ratios

The availability of dissolved iron (Fe) limits primary production over some regions of the surface ocean, especially in regions such as the subarctic North Pacific. In this work, we use Fe stable isotope ratios (δ56Fe) in bulk and size-fractionated marine aerosol particles and dissolved Fe of surface seawater in the subarctic North Pacific on Japanese GEOTRACES cruise GP02 (Summer 2017) as a tracer to clarify the relative contribution of combustion and natural Fe in both marine aerosol particles and surface seawater. The bulk aerosols collected in the coastal regions of both East Asia and western North Pacific have total δ56Fe values that are as low as −0.5 ‰ when compared to crustal (+0.1 ‰), with both the water-soluble phase and the fine particles even more fractionated (as low as −1.9 and −2.8 ‰, respectively). The negative correlation between the aerosol δ56Fe signatures and the enrichment factors of Fe and other elements dominated by anthropogenic sources (e.g., lead and cadmium) in these coastal regions indicates the presence of Fe emitted from high-temperature combustion sources, such as coal combustion and metal smelting. In these regions, combustion Fe accounts for 4–13 and 13–45 % of the total and water-soluble aerosol Fe, respectively. The results demonstrate that soluble aerosol Fe sourced from combustion Fe can be equivalent to that sourced from natural dust Fe in these coastal regions. By contrast, the aerosol particles in pelagic regions were near crustal δ56Fe in all particle size fractions, indicating the dominance of natural Fe and little to no combustion Fe. The relationships among the fractional Fe solubility, major ion concentration, Fe species, and δ56Fe indicate that the presence of combustion Fe is the dominant reason for the solubility increase in the coastal regions and that the atmospheric processing of mineral dust during transport is more important in the pelagic regions. The dissolved Fe of the surface seawater at 10 m depth had a consistently higher δ56Fe by up to +1.5 ‰ than that of the simultaneously collected water-soluble aerosol Fe. The pattern of the elevated δ56Fe in the surface seawater corresponds to decreasing Fe concentrations and can be approximated by Rayleigh fractionation; we attribute these elevated surface δ56Fe values to the effect of biological uptake. New Fe fluxes from both the atmosphere and deeper depths are limited at least in summer compared with the biological uptake in the open ocean of the subarctic North Pacific.

Reactive Molecular Dynamics Simulation Study on Atomic-Scale Adhesive Wear Mechanisms of Single Crystalline Body-Centered Cubic Iron

The adhesive wear of steel is a crucial issue in many industrial fields because it can lead to serious machine failure. However, the adhesive wear mechanism is still under debate owing to its complexity. Therefore, in this work, we performed reactive molecular dynamics-based sliding simulations of single crystalline body-centered cubic iron and investigated the fundamental atomic-scale adhesive wear mechanism for improving the wear resistance of steel. The effects of surface orientation, sliding direction, and humid atmosphere on the adhesive wear property were analyzed. In the sliding simulation, we observed two adhesive wear types. One is the wear accompanying surface deformation, in which the surface asperities gradually deform by slip and adhere severely. The other is the wear accompanying surface fracture with crack generation. The former can lead to seizures, whereas the latter can lead to wear debris formation. We propose that the rubbing surface orientation and sliding direction alter the atomic-scale adhesive wear type. Wear with surface deformation occurred when the deformation by slip was favorable, whereas wear with surface fracture occurred when slip was not favorable. Understanding the adhesive wear mechanism of iron in humid atmospheres is also important in many industrial fields. When water molecules were present at the sliding interface, both types of adhesive wear were suppressed. At the sliding interface, Fe–OH and Fe–O–Fe groups were formed on the scars through the tribochemical reaction with water. These groups passivated the nascent Fe surfaces and suppressed adhesion to the counter surface, thereby reducing adhesive wear. Therefore, we conclude that the surface orientation and sliding direction determine the atomic-scale adhesive wear type, whereas a humid atmosphere affects the wear amount at the atomic scale.

Atmospheric iron deposition in a megacity of northwest China: Solubility, speciation, and deposition fluxes

Atmospheric iron has crucial effects on biogeochemical cycles, atmospheric processing, global climate, and human health. In this study, atmospheric dustfall samples were collected from six functional areas in Xi'an, China, from 2020 to 2021. The spatiotemporal distributions and deposition fluxes of total and water-soluble (ws) Fe as well as the speciation and potential sources of ws-Fe were characterized. Industrial areas had the highest concentrations of total Fe and ws-Fe, which were mainly due to copious emissions of heavy metals during manufacturing. The total Fe concentrations peaked in spring, primarily due to the substantial input of crustal dust, which also led to the lowest Fe solubility in this season. By contrast, the highest levels of ws-Fe occurred during winter due to an increase in biomass combustion. Among the water-soluble forms, ws-Fe (II) was dominant and accounted for 74.8% of the total amount of ws-Fe. Crustal dust was the main contributor to total Fe, whereas biomass burning primarily contributed to peak ws-Fe concentrations. The average total and ws-Fe deposition fluxes in Xi'an were the highest in spring and lowest in autumn, which were related to the distributions of the dustfall deposition fluxes and their Fe contents during these periods. Our study provided a broader and comprehensive understanding of atmospheric iron deposition in Chinese urban area, which is of positive significance for understanding atmospheric chemistry and global climate change.

Direct evidence of pyrogenic aerosol iron by intrusions of continental polluted air into the Eastern China Seas

Atmospheric iron (Fe) is an important micronutrient controlling marine primary productivity, which affects marine ecosystems and biogeochemistry. However, few studies have reported the abundance of aerosol Fe and its associated mixing state and solubility in marine environments. Here, aerosol samples were collected over the Bohai Sea and the Yellow Sea near East China during a research cruise. The results show that anthropogenic Fe-containing particles accounted for 9.3% of the total observed marine particles with diameters from 0.1 to 7 μm. Almost all of the Fe-containing particles (94%) were internal mixtures of FeOx particles (i.e., Fe-rich/fly ash) and secondary aerosols (e.g., nitrate, sulfate, and organics). During their aging process, the FeOx particles grew approximately tenfold in size from 100 nm to 1 μm by acquiring a thick secondary aerosol coating after one to two days of transport. The elemental mapping on a per-particle basis showed that the secondary aerosol coating likely homogeneously contained little Fe, suggesting that the acidic coating solubilized Fe via an acid dissolution process in the marine air. Therefore, acid dissolution of metal aerosols in anthropogenic smog should be considered in studies on the biogeochemical cycle between coastal marine air and ocean productivity.

Aerosol Iron from Metal Production as a Secondary Source of Bioaccessible Iron.

Atmospheric iron (Fe) from anthropogenic, lithogenic, and pyrogenic sources contributes to ocean fertilization, climate change, and human health risk. However, significant uncertainties remain in the source apportionment due to a lack of source-specific evaluation of Fe-laden aerosols. Here, the large uncertainties in the model estimates are investigated using different Fe emissions from metal production. The best agreement in the anthropogenic factor of aerosol Fe concentrations with the field data in the downstream region of East Asian outflow (median: 0.026 μg m-3) is obtained with the low case (0.023 μg m-3), whereas the best agreement of aerosol Fe bioaccessibility with field data (4.5%) over oceans south of 45°S is obtained with the high case (4.9%). Our simulation with the low case confirms that anthropogenic aerosols play dominant roles in bioaccessible Fe deposition in the northwestern Pacific, compared to lithogenic sources. Our simulations with higher cases suggest that Fe-containing particles co-emitted with sulfur dioxide from metal production substantially contribute to atmospheric bioaccessible Fe fluxes to the Southern Ocean. These findings highlight that accurate representation of aerosol Fe from metal production is a key to reduce large uncertainties in bioaccessible Fe deposition fluxes to the Southern Ocean (0.7-4.4 Gg Fe year-1).

Copper ferrite/copper oxides (I, II) nanoparticles synthesized by electric explosion of wires for high performance photocatalytic and antibacterial applications

The CuFe2O4/CuO/Cu2O nanoparticles at the first time have been synthesized by the simultaneous electric explosion of twisted iron and copper wires in an oxygen-containing atmosphere at different copper to iron atomic ratios. The use of nanoparticles with a maximum content of CuFe2O4 as a photocatalyst can reduce the concentration of Congo Red dye in solution by 72% in 60 min at visible light irradiation. Moreover, these nanoparticles exhibited excellent antibacterial activity against MRSA ATCC 43300. The antibacterial activity of the samples is in good agreement with the data on the photocatalytic activity of nanoparticles. This shows that the main mechanism of composite nanoparticles action is based on ROS generation. This study showed that electrical explosion of the metal wires is an attractive method for the synthesis of complex oxides with high photocatalytic and antibacterial activity.

Atmospheric iron particles in PM2.5 from a subway station, Beijing, China

Particulate matter pollution in the subway station's atmosphere can seriously influence the air quality and impacts on the health of subway workers and commuters. In this study, PM2.5 samples were collected from different locations within a subway station in Beijing, and the individual particles were analyzed for morphology and composition by Transmission Electron Microscopy with Energy Dispersive X-ray Spectrometry (TEM-EDX). The results showed that the concentration of PM2.5 in subway stations was affected by both indoor and outdoor sources. Particles generated by train-related sources such as resuspension, wheel, rail, brake and collector shoe abrasion were a significant source of airborne pollution in the subway atmosphere. Within the subway station PM2.5, Fe was the dominant element, and was detected in more than 75% of all particles analyzed. The Fe-rich particles were identified in railway carriages (79.4%), station concourse (65.3%), and platforms (61.3%). The geometric mean diameter of Fe-rich particles was 0.34 μm, which was smaller than that of all detected particles. Cr, Mn and other metals were often detected in the Fe-rich particles, reflecting metal alloys used in the wheels and tracks. A better understanding of the particle distribution around different areas of the subway system and the physicochemical characteristics of these Fe-rich particles is critical in developing a meaningful assessment of the risk posed by particles in the subway atmosphere.

The underappreciated role of anthropogenic sources in atmospheric soluble iron flux to the Southern Ocean

The atmospheric deposition of soluble (bioaccessible) iron enhances ocean primary productivity and subsequent atmospheric CO2 sequestration in iron-limited ocean basins, especially the Southern Ocean. While anthropogenic sources have been recently suggested to be important in some northern hemisphere oceans, the role in the Southern Ocean remains ambiguous. By comparing multiple model simulations with the new aircraft observations for anthropogenic iron, we show that anthropogenic soluble iron deposition flux to the Southern Ocean could be underestimated by more than a factor of ten in previous modeling estimates. Our improved estimate for the anthropogenic iron budget enhances its contribution on the soluble iron deposition in the Southern Ocean from about 10% to 60%, implying a dominant role of anthropogenic sources. We predict that anthropogenic soluble iron deposition in the Southern Ocean is reduced substantially (30‒90%) by the year 2100, and plays a major role in the future evolution of atmospheric soluble iron inputs to the Southern Ocean.

Siderophores as an iron source for picocyanobacteria in deep chlorophyll maximum layers of the oligotrophic ocean

Prochlorococcus and Synechococcus are the most abundant photosynthesizing organisms in the oceans. Gene content variation among picocyanobacterial populations in separate ocean basins often mirrors the selective pressures imposed by the region’s distinct biogeochemistry. By pairing genomic datasets with trace metal concentrations from across the global ocean, we show that the genomic capacity for siderophore-mediated iron uptake is widespread in Synechococcus and low-light adapted Prochlorococcus populations from deep chlorophyll maximum layers of iron-depleted regions of the oligotrophic Pacific and S. Atlantic oceans: Prochlorococcus siderophore consumers were absent in the N. Atlantic ocean (higher new iron flux) but constituted up to half of all Prochlorococcus genomes from metagenomes in the N. Pacific (lower new iron flux). Picocyanobacterial siderophore consumers, like many other bacteria with this trait, also lack siderophore biosynthesis genes indicating that they scavenge exogenous siderophores from seawater. Statistical modeling suggests that the capacity for siderophore uptake is endemic to remote ocean regions where atmospheric iron fluxes are the smallest, especially at deep chlorophyll maximum and primary nitrite maximum layers. We argue that abundant siderophore consumers at these two common oceanographic features could be a symptom of wider community iron stress, consistent with prior hypotheses. Our results provide a clear example of iron as a selective force driving the evolution of marine picocyanobacteria.

Atmospheric Iron and Aluminium Deposition and Sea-Surface Dissolved Iron and Aluminium Concentrations in the South China Sea off Malaysia Borneo (Sarawak Waters)

South China Sea (SCS) is an oligotrophic sea which usually receives low nutrients supply. However, massive atmospheric dust input was occurred during the haze event in Southeast Asia for almost every year. The input of dissolved iron (DFe) and dissolved aluminium (DAl) from dust and nearby land into SCS off Sarawak Borneo region during the worst haze event in 2015 of the Southeast Asia were investigated. The estimation dust deposition during this study was 0.162 mg/m2/yr. The atmospheric fluxes of total Fe and total Al at the offshore Sarawak waters were 0.611 µmol/m2/yr and 2.03 µmol/m2/yr, respectively, where the readily available dissolved Fe and Al from the dust were 0.11 µmol/m2/yr (DFe) and 0.31 µmol/m2/yr (DAl). Fe has higher solubility (17.78%) than Al (15.21%). The lateral fluxes (e.g. from the nearby land) were 37.08 nmol/m2/yr (DFe) and 125 nmol/m2/yr (DAl), with strong Fe organic ligand class L1 (log K:22.43 – 24.33). High concentrations of DFe and DAl at the surface water of the offshore region, coincided with high concentration of macronutrients due to the prevailing south-westerly winds originated from the west Kalimantan. Low residence times, ~0.92 (DFe) and ~1.31 (DAl) years, corresponded well with DAlexcess in surface seawater due to biological utilization of DFe. Future works emphasize on natural organic Fe(III) ligands and phytoplankton study are needed for better understanding on biogeochemistry of Fe and Al at SCS off Malaysia Borneo.

Iron Depletion in the Deep Chlorophyll Maximum: Mesoscale Eddies as Natural Iron Fertilization Experiments

AbstractIn stratified oligotrophic waters, phytoplankton communities forming the deep chlorophyll maximum (DCM) are isolated from atmospheric iron sources above and remineralized iron sources below. Reduced supply leads to a minimum in dissolved iron (dFe) near 100 m, but it is unclear if iron limits growth at the DCM. Here, we propose that natural iron addition events occur regularly with the passage of mesoscale eddies, which alter the supply of dFe and other nutrients relative to the availability of light, and can be used to test for iron limitation at the DCM. This framework is applied to two eddies sampled in the North Pacific Subtropical Gyre. Observations in an anticyclonic eddy center indicated downwelling of iron‐rich surface waters, leading to increased dFe at the DCM but no increase in productivity. In contrast, uplift of isopycnals within a cyclonic eddy center increased supply of both nitrate and dFe to the DCM, and led to dominance of picoeukaryotic phytoplankton. Iron addition experiments did not increase productivity in either eddy, but significant enhancement of leucine incorporation in the light was observed in the cyclonic eddy, a potential indicator of iron stress among Prochlorococcus. Rapid cycling of siderophores and low dFe:nitrate uptake ratios also indicate that a portion of the microbial community was stressed by low iron. However, near‐complete nitrate drawdown in this eddy, which represents an extreme case in nutrient supply compared to nearby Hawaii Ocean Time‐series observations, suggests that recycling of dFe in oligotrophic ecosystems is sufficient to avoid iron limitation in the DCM under typical conditions.

FeI and NiI in cometary atmospheres

FeI and NiI emission lines have recently been found in the spectra of 17 Solar System comets observed at heliocentric distances between 0.68 and 3.25 au and in the interstellar comet 2I/Borisov. The blackbody equilibrium temperature at the nucleus surface is too low to vaporize the refractory dust grains that contain metals, making the presence of iron and nickel atoms in cometary atmospheres a puzzling observation. Moreover, the measured NiI/FeI abundance ratio is on average one order of magnitude larger than the solar photosphere value. We report new measurements of FeI and NiI production rates and abundance ratios for the Jupiter-family comet (JFC) 46P/Wirtanen in its 2018 apparition and from archival data of the Oort-cloud comet (OCC) C/1996 B2 (Hyakutake). The comets were at geocentric distances of 0.09 au and 0.11 au, respectively. The emission line surface brightness was found to be inversely proportional to the projected distance to the nucleus, confirming that FeI and NiI atoms are ejected from the surface of the nucleus or originate from a short-lived parent. Considering the full sample of 20 comets, we find that the range of NiI/FeI abundance ratios is significantly larger in JFCs than in OCCs. We also unveil significant correlations between NiI/FeI and C2/CN, C2H6/H2O, and NH/CN. Carbon-chain- and NH-depleted comets show the highest NiI/FeI ratios. The existence of such relations suggests that the diversity of NiI/FeI abundance ratios in comets could be related to the cometary formation rather than to subsequent processes in the coma.

Iron and nickel atoms in cometary atmospheres even far from the Sun.

In comets, iron and nickel are found in refractory dust particles or in metallic and sulfide grains1. So far, no iron- or nickel-bearing molecules have been observed in the gaseous coma of comets2. Iron and a few other heavy atoms, such as copper and cobalt, have been observed only in two exceptional objects: the Great Comet of 18823 and, almost a century later, C/1965 S1 (Ikeya-Seki)4-9. These sungrazing comets approached the Sun so closely that refractory materials sublimated, and their relative abundance of nickel to iron was similar to that of the Sun and meteorites7. More recently, the presence of iron vapour was inferred from the properties of a faint tail in comet C/2006 P1 (McNaught) at perihelion10, but neither iron nor nickel was reported in the gaseous coma of comet 67P/Churyumov-Gerasimenko by the in situ Rosetta mission11. Here we report that neutral FeI and NiI emission lines are ubiquitous in cometary atmospheres, even far from the Sun, as revealed by high-resolution ultraviolet-optical spectra of a large sample of comets of various compositions and dynamical origins. The abundances of both species appear to be of the same order of magnitude, contrasting the typical Solar System abundance ratio.

High Temperature Oxidation and Decarburization of SiMo Cast Iron in Air and Combustion Atmospheres

Silicon and molybdenum (SiMo) alloyed cast irons with spherical graphite are used for exhaust manifolds for service at high temperatures in air and combustion atmospheres containing water vapor. Analysis of degraded surfaces of in-service manifolds indicates existence of a combined oxidation and de-carburization (de-C) phenomena. Therefore, sequential high-temperature tests in air and combustion atmosphere with recording weight change together with carbon analysis at each time step were utilized to quantify the kinetics of both processes. The recorded weight change was related to weight gain due to oxidation and weight loss due to de-C. Carbon analysis was used to de-couple these two processes. SEM measured thicknesses of de-C layers were used to verify kinetics obtained from changes in carbon concentration during oxidation. It was shown that the oxidation and de-C kinetics have different sensitivities to testing temperature and the type of oxidizing atmospheres. At 700 °C and above, there are several significant mutual effects between scale formation and de-C processes which affect the kinetics of these processes and activation energy. The tested experimental methodology for decoupling these processes can be used for alloy optimization.

Fungal-induced atmospheric iron corrosion in an indoor environment

A multi-disciplinary investigation was undertaken to determine the cause of corrosion of iron nails from a skeletal structure in a museum setting. Corroded iron nails were removed from a large whale skeleton, that had been assembled in the 1930s and exhibited for over 80 years at the Natural History Museum in London, United Kingdom. Oxford Nanopore Technologies sequencing, SEM-EDS imaging and chemical mapping were used to document the fungal and bacterial communities associated with the corrosion of the iron nails. A mechanism for indoor fungal-mediated corrosion (biodeterioration) and biomineralisation of iron is proposed. The mechanism includes the establishment of a biofilm dominated by fungi, a corrosive electrolyte produced by fungal activities, transport of ions and biomineralisation of iron-rich minerals.

Atmospheric iron supply and marine productivity in the glacial North Pacific Ocean

Abstract. Iron (Fe) is a key element in the Earth climate system, as it can enhance marine primary productivity in the high-nutrient low-chlorophyll (HNLC) regions where, despite a high concentration of major nutrients, chlorophyll production is low due to iron limitation. Eolian mineral dust represents one of the main Fe sources to the oceans; thus, quantifying its variability over the last glacial cycle is crucial to evaluate its role in strengthening the biological carbon pump. Polar ice cores, which preserve detailed climate records in their stratigraphy, provide a sensitive and continuous archive for reconstructing past eolian Fe fluxes. Here, we show the Northern Hemisphere Fe record retrieved from the NEEM ice core (Greenland), which offers a unique opportunity to reconstruct the past Fe fluxes in a portion of the Arctic over the last 108 kyr. Holocene Fe fluxes (0.042–11.7 ka, 0.5 mg m−2 yr−1) at the NEEM site were 4 times lower than the average recorded over the last glacial period (11.7–108 ka, 2.0 mg m−2 yr−1), whereas they were greater during the Last Glacial Maximum (LGM; 14.5–26.5 ka, 3.6 mg m−2 yr−1) and Marine Isotope Stage 4 (MIS 4; 60–71 ka, 5.8 mg m−2 yr−1). Comparing the NEEM Fe record with paleoceanographic records retrieved from the HNLC North Pacific, we found that the coldest periods, characterized by the highest Fe fluxes, were distinguished by low marine primary productivity in the subarctic Pacific Ocean, likely due to the greater sea ice extent and the absence of major nutrients upwelling. This supports the hypothesis that Fe fertilization during colder and dustier periods (i.e., LGM and MIS 4) was more effective in other regions, such as the midlatitude North Pacific, where a closer relationship between marine productivity and the NEEM Fe fluxes was observed.

Cu–Fe nanoparticles containing nanocomposites: synthesis, stabilization and antibacterial activity

Currently, soft hydrogels with antimicrobial properties are widely used in biomedical applications as dressings and wound healing agents. In the present work, Cu–Fe nanoparticles with different component ratios were obtained by the joint electric explosion of iron and copper wires in an argon atmosphere. Bimetallic nanoparticles had a clear interface between the iron and copper phases at the particle level. Cu–Fe nanoparticles had high antibacterial activity against a wide bacterial spectrum. In connection with dusting and entrainment of nanoparticles, for the convenience of biomedical application, compositions were created based on non-toxic biocompatible polymers – polyvinyl alcohol, polyacrylic acid, and polyacrylamide. The suspension of nanoparticles was pretreated with ultrasound for 5 min at a frequency of 22.4 kHz. Polyvinyl alcohol was used as a nanoparticle stabilizer. The stability of the suspension was investigated by the sedimentation method. The resulting compositions effectively inhibited the growth of Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, methicillin-resistant Staphylococcus aureus ATCC 43300 (MRSA), and Pseudomonas aeruginisa ATCC 9027.

The atmospheric iron variations during 1950–2016 recorded in snow at Dome Argus, East Antarctica

174 snow samples were collected from a 4.5 m snow pit at Dome Argus (Dome A), East Antarctica, during the 2015–2016 austral summer. They covered a period between 1950 and 2016. These samples were measured for iron (Fe) concentrations by the inductively coupled plasma mass spectrometry (ICP-MS). Both the total dissolvable Fe (TDFe) and dissolved Fe (DFe) were measured in order to evaluate the fractional Fe solubility (FFS), an important variable to determine the Fe availability for biological activities. The results show an average TDFe flux of 0.019 mg m−2 a−1 and DFe flux of 2.254 × 10−3 mg m−2 a−1 at Dome A. The mean FFS of 7.27% is consistent with previous studies on the Antarctic ice sheet. Based on the mean value of the TDFe fluxes from both the current and previous studies, the atmospheric TDFe flux in Antarctic modern snow was estimated at 19–140 × 10−3 mg m−2 a−1, potentially supporting 10.5–76.5 Tg C a−1 of primary production. This accounts about 1.21–8.80% of the annual primary production in the seasonal sea ice zone of Southern Ocean (SO), suggesting that atmospheric DFe is a minor component of Fe supply.

A Mineralogy‐Based Anthropogenic Combustion‐Iron Emission Inventory

AbstractAtmospheric 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.