Effect of oxalate and pH on chrysotile dissolution at 25  C: An experimental study

Rozalén, Marisa; Ramos, M. Elena; Fiore, Saverio; Gervilla, Fernando; Huertas, F. Javier

doi:10.2138/am.2014.4636

Cited by 13 publications

(17 citation statements)

References 47 publications

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“…The similarity in our Fe release rates to those of illite suggests that Fe is mainly released from the reactive surface on Fe-containing minerals by similar mechanisms to aluminosilicates (Fig. S2), which involve inward movement of dissolution from the grain edges (Brandt et al, 2003;Rozalén et al, 2008). Consequently, by applying Eq.…”

Section: Development Of a New Fe Dissolution Scheme Based On New Expementioning

confidence: 65%

“…In laboratory works, the enhanced dissolution rates of elements from phyllosilicate minerals have been observed during the initial period when metals are incongruently dissolved in solution (e.g., Malmström and Banwart, 1997;Brandt et al, 2003). Much slower quasi-steady-state dissolution rates after 10-14 days are typically observed for aluminosilicate minerals in acid solutions (Amram and Ganor, 2005;Lowson et al, 2005;Golubev et al, 2006;Rozalén et al, 2008;Bibi et al, 2011). Recent atmospheric chemical transport models have adopted the initial period of enhanced Fe release rate for the proton-promoted dissolution (Ito and Xu, 2014;Myriokefalitakis et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Delivery of anthropogenic bioavailable iron from mineral dust and combustion aerosols to the ocean

Ito¹,

Shi²

2015

Preprint

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Abstract. Atmospheric deposition of anthropogenic soluble iron (Fe) to the ocean has been suggested to modulate primary ocean productivity and thus indirectly affect the climate. A key process contributing to anthropogenic sources of soluble Fe is associated with air pollution, which acidifies Fe-containing mineral aerosols during their transport and leads to Fe transformation from insoluble to soluble forms. However, there is large uncertainty in our estimate of this anthropogenic soluble Fe. Here, we, for the first time, interactively combined laboratory kinetic experiments with global aerosol modeling to more accurately quantify anthropogenic soluble Fe due to air pollution. We firstly examined Fe dissolution kinetics of African dust samples at acidic pH values with and without ionic species commonly found in aerosol water (i.e., sulfate and oxalate). We then constructed a new empirical scheme for Fe release from mineral dust due to inorganic and organic anions in aerosol water, by using acidity as a master variable. We implemented this new scheme and applied an updated mineralogical emission database in a global atmospheric chemistry transport model to estimate the atmospheric concentration and deposition flux of soluble Fe under preindustrial and modern conditions. Our improved model successfully captured the inverse relationship of Fe solubility and total Fe loading measured over the North Atlantic Ocean (i.e., 1–2 orders of magnitude lower Fe solubility in North African- than combustion-influenced aerosols). The model results show a positive relationship between Fe solubility and water soluble organic carbon (WSOC)/Fe molar ratio, which is consistent with previous field measurements. We estimated that deposition of soluble Fe to the ocean increased from 0.05–0.07 Tg Fe yr−1 in preindustrial era to 0.11–0.12 Tg Fe yr−1 in present days, due to air pollution. Over the High Nitrate Low Chlorophyll (HNLC) regions of the ocean, the modeled Fe solubility remains low for mineral dust (< 1 %) in a base simulation but is substantially enhanced in a sensitivity simulation, which permits the Fe dissolution for mineral aerosols in the presence of excess oxalate under low acidity during daytime. Our model results suggest that human activities contribute to about half of the soluble Fe supply to a significant portion of the oceans in the Northern Hemisphere, while their contribution to oceans in high latitudes remains uncertain due to limited understanding of dust Fe dissolution under pristine conditions.

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Section: Development Of a New Fe Dissolution Scheme Based On New Expementioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Delivery of anthropogenic bioavailable iron from mineral dust and combustion aerosols to the ocean

Ito¹,

Shi²

2015

Preprint

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“…2), previous laboratory studies of single mineral phyllosilicate dissolution in acidic solutions showed that only the curled sheets have been transformed into a nearly pure silica phase, and analyses done around or inside the corroded zone do not show such depletion of Mg, Fe, Al and K (Turpault and Trotignon, 1994). Thus, the dissolution of micas was limited by Si release (Bibi et al, 2014;Rozalen et al, 2014;Turpault and Trotignon, 1994).…”

Section: Discussionmentioning

confidence: 97%

A nano-scale study of the mechanisms of non-exchangeable potassium release from micas

Wang

Zhou

et al. 2015

Applied Clay Science

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“…Over a broader pH range (pH 2–8), dissolution rates of Mg and Si were reported to scale exponentially with pH . Organic chelators such as oxalate, which are commonly observed in soils and were found to be exuded by lichens and fungi in contact with asbestos, enhance Mg dissolution rates of asbestos at acidic and mildly acidic pH values . In soil environments, rates of mineral weathering processes depend on specific chemical conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Many reported studies on chrysotile dissolution have provided valuable insight into the geochemistry of asbestos, but it is difficult to translate their findings to environmental systems such as soils. These include not only acid‐leaching studies, but also dissolution studies in which the pH was not or insufficiently buffered . In some studies very high ligand concentrations were used or pH buffering was done with metal chelators [e.g., (2‐amino‐2‐(hydroxymethyl)propane‐1,3‐diol (Tris) or citrate] without taking into account the effect of these ligands on chrysotile dissolution.…”

Section: Introductionmentioning

confidence: 99%

The Effect of pH and Biogenic Ligands on the Weathering of Chrysotile Asbestos: The Pivotal Role of Tetrahedral Fe in Dissolution Kinetics and Radical Formation

Walter

Schenkeveld

Reissner

et al. 2019

Chemistry A European J

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Chrysotile asbestos is a soil pollutant in many countries. It is a carcinogenic mineral, partly due to its surface chemistry. In chrysotile, Fe II and Fe III substitute Mg octahedra (Fe[6]), and Fe III substitutes Si tetrahedra (Fe[4]). Fe on fiber surfaces can generate hydroxyl radicals (HO . ) in Fenton reactions, which damage biomolecules. To better understand chrysotile weathering in soils, net Mg and Si dissolution rates over the pH range 3.0–11.5 were determined in the presence and absence of biogenic ligands. Also, HO . generation and Fe bulk speciation of pristine and weathered fibers were examined by EPR and Mössbauer spectroscopy. Dissolution rates were increased by ligands and inversely related to pH with complete inhibition at cement pH (11.5). Surface‐exposed Mg layers readily dissolved at low pH, but only after days at neutral pH. On longer timescales, the slow dissolution of Si layers became rate‐determining. In the absence of ligands, Fe[6] precipitated as Fenton‐inactive Fe phases, whereas Fe[4] (7 % of bulk Fe) remained redox‐active throughout two‐week experiments and at pH 7.5 generated 50±10 % of the HO . yield of Fe[6] at pristine fiber surfaces. Ligand‐promoted dissolution of Fe[4] (and potentially Al[4]) labilized exposed Si layers. This increased Si and Mg dissolution rates and lowered HO . generation to near‐background level. It is concluded that Fe[4] surface species control long‐term HO . generation and dissolution rates of chrysotile at natural soil pH.

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Effect of oxalate and pH on chrysotile dissolution at 25 C: An experimental study

Cited by 13 publications

References 47 publications

Delivery of anthropogenic bioavailable iron from mineral dust and combustion aerosols to the ocean

Delivery of anthropogenic bioavailable iron from mineral dust and combustion aerosols to the ocean

A nano-scale study of the mechanisms of non-exchangeable potassium release from micas

The Effect of pH and Biogenic Ligands on the Weathering of Chrysotile Asbestos: The Pivotal Role of Tetrahedral Fe in Dissolution Kinetics and Radical Formation

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