Iron solubility driven by speciation in dust sources to the ocean

Schroth, Andrew W.; Crusius, John; Sholkovitz, Edward R.; Bostick, Benjamín C.

doi:10.1038/ngeo501

Cited by 372 publications

(461 citation statements)

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“…Mezkhidze et al (2003) have assumed that hematite is an important source for the dissolved iron over the North Pacific, because most of the iron in surface soil of the Gobi deserts is found in the form of hematite (a-Fe 2 O 3 ) (Hseung and Jackson, 1952;Claquin et al, 1999). However, the assumption of hematite as the solely important source for dissolved iron may need to be revisited, as more comprehensive experimental data for chemical specificity of iron-rich dust become available (Cwiertny et al, 2008;Journet et al, 2008;Schroth et al, 2009;Fu et al, 2010). Here, the illite dissolution is also considered for specification of "structural iron", which is trapped in the crystal lattice of aluminosilicate minerals (RS4 in Table 1).…”

Section: Mineral Aerosol Dissolutionmentioning

confidence: 99%

“…In addition, cloud processing, which may involve radical reactions in liquid phase, has been suggested to increase the soluble iron particles in the fine mode (Zhu et al, 1992;Shi et al, 2009). The mineralogy of iron also influences the particulate iron solubility and may contribute to the size dependence of the soluble ironrich dust (Claquin et al, 1999;Cwiertny et al, 2008;Journet et al, 2008;Schroth et al, 2009). Compared to mineral dust aerosols, iron from combustion sources is suggested to be more soluble, and found more frequently in smaller particles (Chuang et al, 2005;Guieu et al, 2005;Sedwick et al, 2007;Sholkovitz et al, 2009).…”

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confidence: 99%

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Role of dust alkalinity in acid mobilization of iron

2010

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Abstract. Atmospheric processing of mineral aerosols by acid gases (e.g., SO 2 , HNO 3 , N 2 O 5 , and HCl) may play a key role in the transformation of insoluble iron (Fe in the oxidized or ferric (III) form) to soluble forms (e.g., Fe(II), inorganic soluble species of Fe(III), and organic complexes of iron). On the other hand, mineral dust particles have a potential of neutralizing the acidic species due to the alkaline buffer ability of carbonate minerals (e.g., CaCO 3 and MgCO 3 ). Here we demonstrate the impact of dust alkalinity on the acid mobilization of iron in a three-dimensional aerosol chemistry transport model that includes a mineral dissolution scheme. In our model simulations, most of the alkaline dust minerals cannot be entirely consumed by inorganic acids during the transport across the North Pacific Ocean. As a result, the inclusion of alkaline compounds in aqueous chemistry substantially limits the iron dissolution during the long-range transport to the North Pacific Ocean: only a small fraction of iron (<0.2%) dissolves from hematite in the coarse-mode dust aerosols with 0.45% soluble iron initially. On the other hand, a significant fraction of iron (1-2%) dissolves in the fine-mode dust aerosols due to the acid mobilization of the iron-containing minerals externally mixed with carbonate minerals. Consequently, the model quantitatively reproduces higher iron solubility in smaller particles as suggested by measurements over the Pacific Ocean. It implies that the buffering effect of alkaline content in dust aerosols might help to explain the inverse relationship between aerosol iron solubility and particle size. We also demonstrate that the iron solubility is sensitive to the chemical specification of iron-containing minerals in dust. Compared with the dust sources, soluble iron from combustion sources contributes to a relatively marginal effect for deCorrespondence to: A. Ito (akinorii@jamstec.go.jp) position of soluble iron over the North Pacific Ocean during springtime. Our results suggest that more comprehensive data for chemical specificity of iron-rich dust is needed to improve the predictive capability for size-segregated soluble iron particles.

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Section: Mineral Aerosol Dissolutionmentioning

confidence: 99%

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confidence: 99%

Role of dust alkalinity in acid mobilization of iron

2010

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“…oxidation states, bonding environments and mineralogy Schroth et al, 2009). Thus, due to higher solubility of iron trapped in the crystal lattice of aluminosilicates and the large abundance of clay minerals, Journet et al (2008) suggested that the use of hematite as a single source of DFe in biogeochemical models might cause an underestimation of the DFe supply to the ocean.…”

Section: Implications For Fe Fractional Solubilitymentioning

confidence: 99%

Mapping the physico-chemical properties of mineral dust in western Africa: mineralogical composition

et al. 2014

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Abstract. In the last few years, several ground-based and airborne field campaigns have allowed the exploration of the properties and impacts of mineral dust in western Africa, one of the major emission and transport areas worldwide. In this paper, we explore the synthesis of these observations to provide a large-scale quantitative view of the mineralogical composition and its variability according to source region and time after transport.This work reveals that mineral dust in western Africa is a mixture of clays, quartz, iron and titanium oxides, representing at least 92 % of the dust mass. Calcite ranged between 0.3 and 8.4 % of the dust mass, depending on the origin. Our data do not show a systematic dependence of the dust mineralogical composition on origin; this is to be the case as, in most of the instances, the data represent the composition of the atmospheric burden after 1-2 days after emission, when air masses mix and give rise to a more uniform dust load. This has implications for the representation of the mineral dust composition in regional and global circulation models and in satellite retrievals.Iron oxides account for 58 ± 7 % of the mass of elemental Fe and for between 2 and 5 % of the dust mass. Most of them are composed of goethite, representing between 52 and 78 % of the iron oxide mass. We estimate that titanium oxides account for 1-2 % of the dust mass, depending on whether the dust is of Saharan or Sahelian origin.The mineralogical composition is a critical parameter for estimating the radiative and biogeochemical impact of mineral dust. The results regarding dust composition have been used to estimate the optical properties as well as the iron fractional solubility of Saharan and Sahelian dust.Data presented in this paper are provided in numerical form upon email request while they are being turned into a public database, the Dust-Mapped Archived Properties (DUST-MAP), which is an open repository for compositional data from other source regions in Africa and worldwide.

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“…[20,21] This XANES analysis shows that iron oxyhydroxides and oxides are only part of the particulate iron in the ocean. Journet et al [22] and Schroth et al [23] have both shown that Fe-containing silicates (both clays and primary minerals) from putative atmospheric dust sources can have higher solubility than iron oxides. The abundance of clays and primary and secondary Fe-bearing silicates that we see in the water column begs for the examination of the bioavailability of these particulate iron species.…”

Section: Discussionmentioning

confidence: 99%

Visualising Fe speciation diversity in ocean particulate samples by micro X-ray absorption near-edge spectroscopy

Marcus

Lam

2014

Environ. Chem.

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Environmental context. Iron-bearing particles in the ocean have attracted interest due to the role of iron as an essential nutrient for microscopic algae, which form the base of the marine food chain. Modern techniques make it possible to analyse individual particles of iron to determine their composition, but the resulting flood of data can be overwhelming. We show a method of simplifying the data to answer such questions as what groups of minerals are present and whether they are different between ocean basins.Abstract. It is a well known truism that natural materials are inhomogeneous, so analysing them on a point-by-point basis can generate a large volume of data, from which it becomes challenging to extract understanding. In this paper, we show an example in which particles taken from the ocean in two different regions

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Iron solubility driven by speciation in dust sources to the ocean

Cited by 372 publications

References 24 publications

Role of dust alkalinity in acid mobilization of iron

Role of dust alkalinity in acid mobilization of iron

Mapping the physico-chemical properties of mineral dust in western Africa: mineralogical composition

Visualising Fe speciation diversity in ocean particulate samples by micro X-ray absorption near-edge spectroscopy

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