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• New methods are requested for characterizing asbestos fibers in a mineral matrix. • SEM-Raman imaging is efficient for characterizing mineral fibers in-situ. • Confocal Raman imaging makes 3D analysis possible. • 3D analysis provides information on the aspect ratio and volume fraction of asbestos. • Fibers thinner than 400 nm can be identified by confocal Raman in SEM (λ = 532 nm). Asbestos consists in natural minerals crystallized in a specific habit and possessing in particular properties. In the case of Naturally Occurring Asbestos, usual methods applied to the identification of mineral fibers and the determination of their possible asbestiform nature seems not efficient, especially in the case of mineral fibers included in mineral matrix. We present a new in-situ method based on the use of confocal Raman-in-SEM imaging implemented in a Scanning Electron Microscope as an efficient method for in-situ mineralogy. The limitation of conventional methods is discussed. We applied 2D-Raman imaging to the identification of sub-micrometric fibers included in different mineral matrix. We were able to identify actinolite fibers down to 400 nm in diameter, included in feldspar, quartz and/or calcite matrix. Moreover, Confocal Raman allows the collection of 3D data that would provide access to critical information on the morphology of the amphibole fibers in the volume, such as aspect ratio, fibers distribution and amphibole volume fraction. We performed this method on various examples of rocks containing actinolite fibers of mean structural formula is: Na 0,04-0,12 Mg 2,79-3,73 Al 0,29-0,58 K 0,01 Ca 1,79-1,98 Mn 0,01-0,09 Fe2+ 0,99-1,91 Fe3+Si 7,64-7,73 O 22 (OH) 2. We demonstrated that coupling confocal Raman imaging and SEM is a new and efficient in-situ method for identification and morphological characterization of amphibole fibers. [ABSTRACT FROM AUTHOR]

In Naturally Occurring Asbestos (NOA) rich areas, water flows through asbestos bearing rocks and soils and generates waterborne fibres that may migrate in air and become a risk for humans. Research on the migration and dispersion after water vaporisation has been so far only marginally evaluated. This study investigates the migration in air of asbestos from a set of suspensions contaminated by chrysotile from Balangero (Italy), under controlled laboratory conditions. We evaluated i) the morphological modifications that might occur to chrysotile during migration from water to air, and ii) the amount of airborne chrysotile mobilised from standardised suspensions. Morphological alteration of asbestos fibres occurred during water-air migration and impacted on the analytical response of electron microscopy. Waterborne asbestos concentration higher than 40 ∙ 106 f/L generates in air concentration higher than 1 fibre per litre [f/L], the alarm threshold limit set by World Health Organization for airborne asbestos. A possible correlation between the waterborne fibre concentration as mass or number of fibres per volume unit [μg/L or f/L] was observed. [Display omitted] • A device is created to simulate and quantify water-to-air migration of asbestos. • Waterborne chrysotile asbestos migrates in air following turbulent motion of water. • A chrysotile waterborne concentration of 40·106 f/L generates > 1 f/L in air. [ABSTRACT FROM AUTHOR]