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Surface alteration mechanism and topochemistry of iron in tremolite asbestos: A step toward understanding the potential hazard of amphibole asbestos

TitoloSurface alteration mechanism and topochemistry of iron in tremolite asbestos: A step toward understanding the potential hazard of amphibole asbestos
Tipo di pubblicazioneArticolo su Rivista peer-reviewed
Anno di Pubblicazione2015
AutoriPacella, A., Fantauzzi M., Turci F., Cremisini C., Montereali Maria Rita, Nardi Elisa, Atzei D., Rossi A., and Andreozzi G.B.
RivistaChemical Geology
Volume405
Paginazione28-38
ISSN00092541
Parole chiaveAmorphous nanoparticles, amphibole, Asbestos, chemical alteration, Congruent dissolutions, Dissolution, Electron microscopy, hazard assessment, High resolution transmission electron microscopy, Incongruent dissolutions, Inductively coupled plasma, Inductively coupled plasma-optical emission spectrometry, Iron, Italy, Maryland, Multi-technique approach, Naturally occurring, Optical emission spectroscopy, oxidation, Photoelectrons, Photons, Spectrometry, Structural modifications, Surface chemistry, Toxicity, Transmission electron microscopy, Tremolite, United States, X ray photoelectron spectroscopy, X-ray spectroscopy
Abstract

Non-occupational, environmental and unintentional exposure to fibrous tremolite, one of the most widespread naturally occurring asbestos, represents a potentially significant geological risk in several parts of the world. The toxicity of amphibole asbestos is commonly related to iron content and oxidation state, but information available on surface iron topochemistry and amphibole alteration mechanism is still rather poor. With the aim to shed a light on this mechanism, two tremolite samples, one from Italy (Castelluccio) and one from USA (Maryland), immersed in a buffer solution (pH7.4) with H2O2 were characterized by a multi-technique approach. X-ray photoelectron spectroscopy (XPS) and high resolution-transmission electron microscopy (HR-TEM) were used to investigate the surface chemistry of the incubated samples and to detect structural modifications of the fibres, while inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the concentration of dissolved elements.An original four-step model for amphibole alteration pathway is proposed. The alteration process starts with an incongruent dissolution of the amphiboles that produces an amorphous, altered surface layer and that is followed by iron oxidation and formation of FeOOH species. Then the congruent dissolution of the altered layer starts and, subsequently, the residual Fe oxi-hydroxides aggregates and insoluble, Fe-rich, amorphous nanoparticles on top of the fibres are formed. The results are compared to those obtained on crocidolite, a highly toxic amphibole asbestos with a 10 to 20 times higher iron content than tremolite. The high chemical reactivity observed in the literature for tremolite appears to be related not only to its iron content and oxidation state, but also to the low nuclearity of iron on the altered surfaces, in contrast to pronounced Fe clusterization at crocidolite surfaces. This is a significant step toward a conceivable explanation of why asbestos tremolite is potentially as toxic as crocidolite. © 2015 Elsevier B.V.

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URLhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-84928739339&doi=10.1016%2fj.chemgeo.2015.03.028&partnerID=40&md5=1e10a8fab57ad285c8cc28c046c11b7d
DOI10.1016/j.chemgeo.2015.03.028
Citation KeyPacella201528