Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing

Shi, Zongbo; Bonneville, Steeve; Krom, Michael D.; Carslaw, K. S.; Jickells, Timothy D.; Baker, Alex R.; Benning, Liane G.

doi:10.5194/acp-11-995-2011

Cited by 131 publications

(188 citation statements)

References 63 publications

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“…The precision of the ferrozine method was ±1.2 % (1σ , n = 6) (Shi et al, 2011a), while the precision of the ICP-MS Fe technique was ±2.3 % (1σ , n = 6) using the CRM SLRS-4. In addition, to verify the efficacy of the total trace metal digestion, the FeT in the Tibesti-PM 20 and Western Sahara-PM 20 samples was compared with total Fe determined by X-ray Fluorescence (XRF) (Shi et al, 2011b). FeT in these two samples was 4.6 % and 4.4 %, similar to 4.8 % and 4.7 % measured by XRF (Shi et al, 2011a, b).…”

Section: Dissolved Fe and Al Extraction Sample Digestion And Trace mentioning

confidence: 64%

Minor effect of physical size sorting on iron solubility of transported mineral dust

et al. 2011

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Abstract.Observations show that the fractional solubility of Fe (FS-Fe, percentage of dissolved to total Fe) in dust aerosol increases considerably from 0.1 % in regions of high dust mass concentration to 80 % in remote regions where concentrations are low. Here, we combined laboratory geochemical measurements with global aerosol model simulations to test the hypothesis that the increase in FS-Fe is due to physical size sorting during transport. We determined the FS-Fe and fractional solubility of Al (FS-Al) in size-fractionated dust generated from two representative soil samples collected from known Saharan dust source regions using a customized dust re-suspension and collection system. The results show that the FS-Fe is size-dependent and ranges from 0.1-0.3 % in the coarse size fractions (>1 µm) to ∼0.2-0.8 % in the fine size fractions (<1 µm). The FSAl shows a similar size distribution to that of the FS-Fe. The size-resolved FS-Fe data were then combined with simulated dust mass concentration and size distribution data from a global aerosol model, GLOMAP, to calculate the FS-Fe of dust aerosol over the tropical and subtropical North Atlantic Ocean. We find that the calculated FS-Fe in the dust aerosol increases systematically from ∼0.1 % at high dust mass concentrations (e.g., >100 µg m −3 ) to ∼0.2 % at low concentrations (<100 µg m −3 ) due to physical size sorting (i.e., particle gravitational settling). These values are one to two orders of magnitude smaller than those observed on cruises across the tropical and sub-tropical North Atlantic Ocean under an important pathway of Saharan dust plumes for simiCorrespondence to: Z. B. Shi (z.shi@bham.ac.uk) lar dust mass concentrations. Even when the FS-Fe of submicrometer size fractions (0.18-0.32 µm, 0.32-0.56 µm, and 0.56-1.0 µm) in the model is increased by a factor of 10 over the measured values, the calculated FS-Fe of the dust is still more than an order of magnitude lower than that measured in the field. Therefore, the physical sorting of dust particles alone is unlikely to be an important factor in the observed inverse relationship between the FS-Fe and FS-Al and the atmospheric mineral dust mass concentrations. The results suggest that processes such as chemical reactions and/or mixing with combustion particles are the main mechanisms to cause the increased FS-Fe in long-range transported dust aerosols.

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Section: Dissolved Fe and Al Extraction Sample Digestion And Trace mentioning

confidence: 64%

Minor effect of physical size sorting on iron solubility of transported mineral dust

et al. 2011

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“…Similar processes are known to affect the fraction of bioavailable Fe in mineral dust (e.g. Shi et al, 2009Shi et al, , 2011b. The interaction between these two elements in atmospheric aerosols will no doubt be the subject of future research.…”

Section: Discussionmentioning

confidence: 99%

Atmospheric acidification of mineral aerosols: a source of bioavailable phosphorus for the oceans

et al. 2011

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Abstract. Primary productivity of continental and marine ecosystems is often limited or co-limited by phosphorus. Deposition of atmospheric aerosols provides the major external source of phosphorus to marine surface waters. However, only a fraction of deposited aerosol phosphorus is water soluble and available for uptake by phytoplankton. We propose that atmospheric acidification of aerosols is a prime mechanism producing soluble phosphorus from soil-derived minerals. Acid mobilization is expected to be pronounced where polluted and dust-laden air masses mix. Our hypothesis is supported by the soluble compositions and reconstructed pH values for atmospheric particulate matter samples collected over a 5-yr period at Finokalia, Crete. In addition, at least tenfold increase in soluble phosphorus was observed when Saharan soil and dust were acidified in laboratory experiments which simulate atmospheric conditions. Aerosol acidification links bioavailable phosphorus supply to anthropogenic and natural acidic gas emissions, and may be a key regulator of ocean biogeochemistry.

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“…Under natural soil conditions, Fe(III) occurs bound to minerals, such as hematite, that are not soluble in water (Isaac, 1997;Zhu, 1997) and Fe dissolution is dependent on the water's ligand capacity as well as on the type and quantity of dust deposited on the surface (Mendez, 2010;Shi et al, 2011). An atmospheric process, particle aging, including photoreduction and proton reactions, controls variations in oxidation state, solubility, and bioavailability of iron oxides in dust and determines the ultimate influence these materials have on environmental and biological processes (Siefert et al, 1994;Reynolds et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Soluble iron nutrients in Saharan dust over the central Amazon rainforest

et al. 2017

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The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and its long-range transport might be an important source for the iron-limited Amazon rainforest. This study assesses the bioavailability of iron Fe(II) and Fe(III) in the particulate matter over the Amazon forest, which was transported from the Sahara desert (for the sake of our discussion, this term also includes the Sahel region). The sampling campaign was carried out above and below the forest canopy at the ATTO site (Amazon Tall Tower Observatory), a near-pristine area in the central Amazon Basin, from March to April 2015. Measurements reached peak concentrations for soluble Fe(III) (48 ng m−3), Fe(II) (16 ng m−3), Na (470 ng m−3), Ca (194 ng m−3), K (65 ng m−3), and Mg (89 ng m−3) during a time period of dust transport from the Sahara, as confirmed by ground-based and satellite remote sensing data and air mass backward trajectories. Dust sampled above the Amazon canopy included primary biological aerosols and other coarse particles up to 12 µm in diameter. Atmospheric transport of weathered Saharan dust, followed by surface deposition, resulted in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust, rich in soluble iron, and other minerals is likely to assist both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent species. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence of this input on the ecology of the forest canopy and topsoil is discussed, and we argue that this influence would likely be different from that of nutrients from the weathered Amazon bedrock, which otherwise provides the main source of soluble mineral nutrients

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Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing

Abstract: Abstract. We investigated the iron (Fe) dissolution kinetics of African (Tibesti) and Asian (Beijing) dust samples at acidic pH with the aim of reproducing the low pH conditions in atmospheric aerosols. The Beijing dust and three size fractions of the Tibesti dust (<20 µm: PM 20

Cited by 131 publications

References 63 publications

Minor effect of physical size sorting on iron solubility of transported mineral dust

Minor effect of physical size sorting on iron solubility of transported mineral dust

Atmospheric acidification of mineral aerosols: a source of bioavailable phosphorus for the oceans

Soluble iron nutrients in Saharan dust over the central Amazon rainforest

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